Post on 16-Oct-2021
transcript
Issue Date January 31, 2006
© 2006 Johnson Controls, Inc. www.johnsoncontrols.com Code No. LIT-6375080
APPLICATION NOTE
AHU Applications
Using AHU Applications .......................................................................3
Introduction......................................................................................................... 3
Key Concepts...................................................................................................... 4
AHU Applications ..............................................................................................................4 Mixed Air Single Path Applications ...................................................................................5 100% Outside Air Single Path Applications ....................................................................18 Mixed Air Dual Path or 100% Outside Air Dual Path Applications .................................. 20 Heat Recovery for 100% Outside Air Applications..........................................................25 Economizer .....................................................................................................................27 Preheat............................................................................................................................ 31 Heating............................................................................................................................ 37 Cooling ............................................................................................................................ 42 Dehumidification..............................................................................................................47 Humidification.................................................................................................................. 49 Modes of Operation.........................................................................................................51 Fan System .....................................................................................................................58 Using an AHU Application in a UNT Controller ...............................................................62
Procedure Overview......................................................................................... 64
Detailed Procedures......................................................................................... 65
Creating a Mixed Air Single Path Application..................................................................65 Creating a 100% Outside Air Single Path Application..................................................... 68 Creating a Mixed Air Dual Path or 100% Outside Air Dual Path Application .................. 69 Completing the Heat Recovery for 100% Outside Air Question/Answer Path ................ 70 Completing the Economizer Question/Answer Path .......................................................72 Completing the Minimum Duct Requirements Question/Answer Path ............................ 75 Completing the Vent and Purge Question/Answer Path .................................................79
AHU Applications Application Note 2
Completing the Preheat Question/Answer Path..............................................................81 Completing the Heating Question/Answer Path..............................................................89 Completing the Cooling Question/Answer Path ..............................................................98 Completing the Dehumidification Question/Answer Path..............................................106 Completing the Humidification Question/Answer Path..................................................109 Completing the Modes of Operation Question/Answer Path.........................................111 Completing the Fan System Control Question/Answer Path......................................... 117
Troubleshooting ............................................................................................. 125
Downloading an AHU Application ................................................................................. 125 Saving an AHU Application File for a UNT Controller ................................................... 126
Point Assignments and Parameters ............................................................. 127
Default Point Assignments ............................................................................................127 Default Parameters ......................................................................................................*131
AHU Applications Application Note 3
Using AHU Applications
Introduction The AHU (Air Handling Unit) application is capable of controlling many different air handlers and control strategies. This application note introduces AHU applications and provides procedures for configuring these applications using the question/answer path. This application note describes how to:
• create a mixed air single path application
• create a 100% outside air single path application
• create a mixed air dual path or 100% outside air dual path application
• complete the heat recovery for 100% outside air question/answer path
• complete the economizer question/answer path
• complete the minimum duct requirements question/answer path
• complete the vent and purge question/answer path
• complete the preheat question/answer path
• complete the heating question/answer path
• complete the cooling question/answer path
• complete the dehumidification question/answer path
• complete the humidification question/answer path
• complete the modes of operation question/answer path
• complete the fan system control question/answer path
AHU Applications Application Note 4
Key Concepts AHU Applications
The AHU application is capable of controlling many different air handlers and control strategies (Figure 1). The types of air handling applications that can be controlled include:
• Mixed Air Single Path
• Mixed Air Dual Path
• 100% Outside Air Single Path
• 100% Outside Air Dual Path
Air Handlers100% Outside Air
Dual Path
FLWCHT3
New
File
Air HandlersMixed Air
Single Path
Air HandlersMixed Air Dual Path
Air Handlers100% Outside Air
Single Path
Open
Select Existing File Name
Figure 1: AHU Application Path Each of these applications are explained in the following topics. Use the Table of Contents at the beginning of this document to locate the application you are using. Every question is listed for the entire AHU application, along with explanations for each answer. The AHU controller can be downloaded as a generic point multiplexer. The unused points can be user defined and used with up to 16 sideloops.
AHU Applications Application Note 5
Mixed Air Single Path Applications
Schematic Figure 2 is a schematic of a mixed air single path application.
AirflowStatusExhaust
N.C.
Mixed Air Dampers N.O.
N.C.Outside
Note:Coil arrangement may differ:- Preheat coil may be in the outside air duct before the mixed air sensor.- Heating coil may be after the cooling coil for dehumidification control.- Heating and/or cooling coil may be after the supply fan.
Mixed AirTemperature
PreheatTemperature
PreheatCoil
HeatingCoil
CoolingCoil Supply
Fan
ReturnFan
AirflowStatus
AirflowStation
AirflowStation
Humidifier
Return
Discharge
StaticPressureDischarge
AirTemperature
MASPDUCT
Return Air Temperature and
Humidity
Figure 2: Mixed Air Single Path Schematic
Control Strategy The first question in the mixed air single path question/answer path (Figure 50) asks you to select the control strategy. The available strategies are:
• Room Control
• Room Control of Cooling, Room Reset of Heating
• Supply Air Reset from Zone Temperature (Mixed Air)
• Return Air Control
• Constant Discharge Air Temperature
• Supply Air Reset from Return Temerature The following provides information on each of the six available strategies.
AHU Applications Application Note 6
Room Control The Room Control strategy uses the zone temperature to directly control each controlled device (Figure 3). As the zone temperature decreases into the heating proportional band, the system commands the preheat (if selected and sequenced) and heating devices in sequence. As the zone temperature increases above the zone cooling setpoint, the system controls the outdoor air damper (if selected and sequenced) and mechanical cooling device in sequence. As the zone temperature travels through the various proportional bands, the output to the associated controlled device ranges from 0 to 100%. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
AHU Applications Application Note 7
MA
SPR
AC
.cdr
Occupied
MaximumSelect
Logic
Multiply
0 - 1
EconomizerCommand
Return SetpointHeating DeadbandHeating Proportional BandPreheat Proportional BandHeating IntegrationEconomizer Proportional BandCooling DeadbandCooling Proportional BandCooling IntegrationReturn Air Temperature
Heating Command
Preheat Command
Cooling Command
Economizer Command
Go ToEconomizerSwitchover
Logic
Economizer
0
SupplyAirflow Shutdown
0
HeatingIntegration
Term
0
SupplyAirflow
Shutdown
0
CoolingIntegration
Term
0
Separate Mixed Air Closed Loop
100%
02 1
1 Mixed Air SetpointMixed Air Prop Band2
Mixed Air Integration TermMixed Air Deadband
Mixed Air Temperature
Economizer Command
Mixed Air Low Limit
1
02
1
12
Mixed Air Low Limit Setpoint
Mixed Air Low Limit Proportional Band
Mixed Air Temperature
Mixed Air Low LimitDeadbandMixed Air Low LimitIntegration Term
SupplyAirflow Shutdown
0
Mixed AirLow Limit
IntegrationTerm
0
Single PI
Return Control Sequencer
PHTGHTG
ECONCLG
3
2
14
1234
5
6
7567
Mixed AirLow Limit
Offset
MinimumPosition*
*See
the
section for more information.
Is Minimum Damper Position Reset from an Air Quality Sensor Needed?
Figure 3: Room Control
AHU Applications Application Note 8
Room Control of Cooling, Room Reset of Heating This control strategy uses the zone temperature to reset a discharge air heating setpoint and directly control the cooling device (Figure 4). As the zone temperature increases above the zone cooling setpoint, the system controls the outdoor air damper (if selected and sequenced) and mechanical cooling device in sequence. As the zone temperature travels through the proportional band, the output to the associated controlled device ranges from 0 to 100%. The controller calculates a discharge heating setpoint based on the input heating reset schedule. The discharge heating low limit establishes a calculated discharge setpoint when the zone temperature first enters the zone heating proportional band. The system adds the discharge heating reset band to this low limit. This value is the number of degrees the discharge setpoint changes as the zone temperature decreases through the zone heating proportional band. The discharge sensor then controls and sequences the preheat (if selected and sequenced) and heating device as the discharge temperature decreases below the calculated discharge setpoint. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control. The heating device will remain active when cooling is locked out based on the outside air temperature. This maintains a discharge heating low limit even when the zone temperature is in the cooling proportional band.
AHU Applications Application Note 9
SupplyAirflow
Shutdown
0
HeatingIntegration
Term
0
SupplyAirflow
Shutdown
0
CoolingIntegration
Term
0
MAS
PR
CR
R.c
dr
Economizer Command
Heating SetpointDischarge Htg Prop BandDischarge Htg IntegrationDischarge Preheat Prop BandDischarge Sensor
Economizer LogicOccupied
Mixed Air LowLimit Offset
Occupied
0 - 1
Heating Control 100%
0
0
ECON
Sequencer
CLGHTGReset
Zone SetpointHeating DeadbandHeating Proportional BandHeating IntegrationDischarge Heating Low LimitDischarge Heating Reset BandEconomizer Proportional BandCooling DeadbandCooling Proportional BandCooling IntegrationZone Temperature
0
Heating Command
Preheat Command
Multiply MaximumSelect
1
4
3 2
5
6
7
Discharge Heating SetpointCooling CommandEconomizer Command
Separate Mixed Air Closed Loop
100%
02 1
1 Mixed Air SetpointMixed Air Prop Band2
Mixed Air Integration TermMixed Air Deadband
Mixed Air TemperatureEconomizer Command
1
02
1
12
Mixed Air Low Limit Setpoint
Mixed Air Low Limit Proportional Band
Mixed Air Temperature
Mixed Air Low LimitDeadbandMixed Air Low LimitIntegration Term
SupplyAirflow Shutdown
0
Mixed AirLow Limit
IntegrationTerm
0
Single PI
8
123
45 678
Mixed AirLow Limit
Go ToEconomizerSwitchover
Logic
MinimumPosition*
*See
the section
for more information.
Is Minimum Damper Position Reset from an Air Quality Sensor Needed?
Figure 4: Room Control of Cooling, Room Reset of Heating
AHU Applications Application Note 10
Supply Air Reset from Zone Temperature (Mixed Air) The supply air reset from zone temperature strategy resets the discharge air setpoint for heating and cooling (Figure 5). The zone proportional band is divided by two and each half is active above and below the zone setpoint. As the zone temperature varies away from the zone setpoint within the zone proportional band, it calculates the actual discharge setpoint based on a discharge low limit and discharge reset band. This strategy uses a discharge sensor to control heating and cooling around the actual discharge setpoint. It controls and sequences the preheat (if selected and sequenced) and heating devices as the discharge temperature decreases below the actual discharge setpoint minus the heating deadband. The discharge sensor also controls the outside air damper (if selected and sequenced) and mechanical cooling device as the discharge air temperature increases above the actual discharge setpoint plus the cooling deadband. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
AHU Applications Application Note 11
HTGPHTG ECON
CLG
2
MA
SPA
RZT
.cdr
Discharge SetpointHeating DeadbandHeating Integration TimeHeating Proportional BandPreheat Proportional BandEconomizer Proportional BandCooling DeadbandCooling Integration TimeCooling Proportional BandDischarge Temperature
Go ToEconomizerSwitchover
Logic
Preheat CommandHeating CommandCooling CommandEconomizer Command
Occupied
MaximumSelect
Multiply
0 - 1
EconomizerCommand
0
43
5 6
7
1
0
12
2
1
1
2
21
1 Zone Setpoint
Zone Integration Time
Discharge Low Limit
Discharge Reset Band
Reset BandZone PI
0-100%
Zone Temperature
2
Separate Mixed Air Closed Loop
100%
0 2 1
1 Mixed Air SetpointMixed Air Prop Band2
Mixed Air Integration TermMixed Air Deadband
Mixed Air Temperature
Economizer Command
2
1 Mixed Air Low Limit SetpointMixed Air Low Limit Proportional Band
Mixed Air Temperature
Mixed Air Low LimitDeadbandMixed Air Low LimitIntegration Term
DischargeSetpoint
0% 100%
Single PI
1
12
345 6
7
SupplyAirflow
Shutdown
0
HeatingIntegration
Term
0
SupplyAirflow
Shutdown
0
CoolingIntegration
Term
0
SupplyAirflow
Shutdown
0
Mixed AirLow Limit
IntegrationTerm
0
SupplyAirflow Shutdown
0
Mixed AirLow Limit
IntegrationTerm
0
2 Zone Proportional Band 2
EconomizerLogic
Mixed AirLow Limit
Offset
Discharge Temperature Loop
Mixed Air Low Limit
MinimumPosition*
*See
the section
for more information.
Is Minimum Damper Position Reset from an Air Quality Sensor Needed?
Figure 5: Supply Air Reset from Zone Temperature
AHU Applications Application Note 12
Return Air Control The return air control strategy uses the return air temperature to directly control each controlled device (Figure 6). This strategy commands the preheat (if selected and sequenced) and heating devices in sequence as the return air temperature decreases below the return setpoint minus a heating deadband. As the return temperature increases above the return air setpoint, the return air control strategy controls the outdoor air damper (if selected and sequenced) and mechanical cooling devices in sequence. As the return air temperature varies through the heating and cooling proportional bands, the output to the controlled device ranges between 0 to 100%. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
AHU Applications Application Note 13
MASPRAC
Occupied
MaximumSelect
Logic
Multiply
0 - 1
EconomizerCommand
Return SetpointHeating DeadbandHeating Proportional BandPreheat Proportional BandHeating IntegrationEconomizer Proportional BandCooling DeadbandCooling Proportional BandCooling IntegrationReturn Air Temperature
Heating Command
Preheat Command
Cooling Command
Economizer Command
MinimumPosition
Go ToEconomizerSwitchover
Logic
Economizer
0
SupplyAirflow Shutdown
0
HeatingIntegration
Term
0
SupplyAirflow
Shutdown
0
CoolingIntegration
Term
0
Separate Mixed Air Closed Loop
100%
02 1
1 Mixed Air SetpointMixed Air Prop Band2
Mixed Air Integration TermMixed Air Deadband
Mixed Air Temperature
Economizer Command
Mixed Air Low Limit
1
02
1
12
Mixed Air Low Limit SetpointMixed Air Low Limit Proportional Band
Mixed Air Temperature
Mixed Air Low LimitDeadbandMixed Air Low LimitIntegration Term
SupplyAirflow Shutdown
0
Mixed AirLow Limit
IntegrationTerm
0
Single PI
Return Control Sequencer
PHTGHTG
ECONCLG
3
2
14
1234
5
6
7567
Mixed AirLow Limit
Offset
Figure 6: Return Air Control
AHU Applications Application Note 14
Constant Discharge Air Temperature The constant discharge air temperature strategy uses the discharge air temperature to directly control each controlled device (Figure 7). It commands, in sequence, the preheat (if selected and sequenced) and heating device as the discharge air temperature decreases into the heating proportional band. As the discharge temperature increases above the discharge air setpoint, the system controls the outdoor air damper (if selected and sequenced) and mechanical cooling devices in sequence. As the discharge temperature varies through heating and cooling proportional bands, the output to the controlled device ranges between 0 to 100%. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
AHU Applications Application Note 15
MA
SPC
DC
.cdr
Occupied
MaximumSelectMultiply
0 - 1Command
Discharge SetpointHeating DeadbandHeating Integration TimeHeating Proportional BandPreheat Proportional BandEconomizer Proportional BandCooling DeadbandCooling Integration TimeCooling Proportional BandDischarge Temperature
Economizer LogicSee Economizer Switchover Logic
0
Preheat Command
Heating Command
Cooling Command
Economizer Command
Mixed AirLow Limit
Offset
Go ToEconomizerSwitchover
Logic
Economizer
SupplyAirflow
Shutdown
0
HeatingIntegration
Term
0
SupplyAirflow
Shutdown
0
CoolingIntegration
Term
0
Separate Mixed Air Closed Loop
100%
0 2 1
1 Mixed Air Setpoint orDischarge Air SetpointMixed Air Prop Band2
Mixed Air Integration TermMixed Air Deadband
Mixed Air Temperature Economizer Command
Mixed Air Low Limit
1
02
1
12
Mixed Air Low Limit SetpointMixed Air Low Limit Proportional Band
Mixed Air Temperature
Mixed Air Low LimitDeadbandMixed Air Low LimitIntegration Term
SupplyAirflow
Shutdown
0Mixed AirLow LimitIntegration
Term
0
User-Selected Setpoint for Mixed Air Control
SupplyAirflow Shutdown
0
Mixed AirLow Limit
IntegrationTerm
0
Single PI
3
21
456
7
Discharge Control Sequencer
PHTGHTG
ECONCLG
32
14 5
76
MinimumPosition*
*See
the
section for more information.
Is Minimum Damper Position Reset from an Air Quality Sensor Needed?
Figure 7: Constant Discharge Air Control
AHU Applications Application Note 16
Supply Air Reset from Return Temperature The supply air reset from return temperature strategy resets the discharge air setpoint for heating and cooling (Figure 8). As the return temperature varies below the return high limit and within the return reset band, it calculates a discharge setpoint based on a discharge low limit and discharge reset band. The return proportional band is divided and active above and below the return setpoint. The discharge low limit establishes the discharge setpoint when the return temperature is at the warmest end of the return proportional band. The value of the discharge reset band is the number of degrees added to the discharge low limit as the return temperature decreases through the return proportional band. This strategy uses a discharge sensor to control heating and cooling around the calculated discharge setpoint. It controls and sequences the preheat (if selected and sequenced) and heating devices as the discharge temperature decreases below the calculated discharge setpoint minus the heating deadband. The discharge sensor also controls the outside air damper (if selected and sequenced) and mechanical cooling device as the discharge air temperature increases above the calculated discharge setpoint. As discharge temperature varies through the heating and cooling proportional bands, the outputs to the controlled devices modulate between 0 to 100%. Integration may be added to these control loops to eliminate the inherent offset associated with proportional only control. Economizer Command may include resetting the minimum position see Figure 8, based on indoor air quality. See the Is Minimum Damper Position Reset from an Air Quality Sensor Needed? section for more information.
AHU Applications Application Note 17
HTGPHTG ECON
CLG
2
MASPSART
Discharge SetpointHeating DeadbandHeating Integration TimeHeating Proportional BandPreheat Proportional BandEconomizer Proportional BandCooling DeadbandCooling Integration TimeCooling Proportional BandDischarge Temperature
Discharge Temperature Loop
Go ToEconomizerSwitchover
Logic
Preheat Command
Heating Command
Cooling Command
Economizer Command
Occupied
MaximumSelectMultiply
0 - 1
EconomizerCommand
MinimumPosition*
0
43 5 6
7
Mixed Air Low Limit
1
0
12
Return High LimitReturn Reset BandDischarge Low LimitDischarge Reset BandReturn Air Temperature
Reset Band
Separate Mixed Air Closed Loop
100%
0 2 1
1 Mixed Air SetpointMixed Air Prop Band2
Mixed Air Integration TermMixed Air Deadband
Mixed Air TemperatureEconomizer Command
2
1 Mixed Air Low Limit SetpointMixed Air Low Limit Proportional Band
Mixed Air SensorMA-T
Mixed Air Low LimitDeadbandMixed Air Low LimitIntegration Term
1
SupplyAirflow
Shutdown
0
HeatingIntegration
Term
0
SupplyAirflow
Shutdown
0
CoolingIntegration
Term
0
SupplyAirflow
Shutdown
0
Mixed AirLow Limit
IntegrationTerm
0
2
345 6
7 1
EconomizerLogic
Mixed AirLow Limit
Offset
*See
the section
for more information.
Is Minimum Damper Position Reset from an Air Quality Sensor Needed?
Figure 8: Supply Air Reset from Return Temperature
AHU Applications Application Note 18
100% Outside Air Single Path Applications
Schematic Figure 9 is a schematic of a 100% outside air single path application.
AirflowStatus
Exhaust
N.C.
Outside
Note:Coil arrangement may differ:- Heating coil may be after the cooling coil for dehumidification control.- Heating and/or cooling coil may be after the supply fan.
PreheatTemperature
PreheatCoil
HeatingCoil
CoolingCoil Supply
Fan
ExhaustFan
AirflowStatus
AirflowStation
AirflowStation
Humidifier
Return
Discharge
StaticPressureDischarge
Air Temperature
OASPDUCT
Exhaust AirTemperature
andHumidity
N.C.
Figure 9: 100% Outside Air Single Path Schematic
Question/Answer Path The questions and answers for 100% Outside Air Single Path (OASP) are identical to those for Mixed Air Single Path (MASP), with a few exceptions:
• 100% OASP provides exhaust air temperature control, instead of return air control as in MASP.
• Supply air reset from exhaust temperature is not available for 100% OA units, as supply air reset from return temperature was available for MASP units.
• The supply air reset from zone temperature is unique for 100% OA.
• There is no economizer section for 100% OA control, so when finished with this section, see the Heat Recovery for 100% Outside Air Applications section.
AHU Applications Application Note 19
Supply Air Reset from Zone Temperature (100% OA Single Path) The supply air reset from zone temperature strategy resets the discharge air setpoint for heating and cooling (Figure 10). As the zone temperature rises into the zone cooling proportional band, it calculates a discharge setpoint based on a discharge cooling low limit and discharge cooling reset band. When the zone temperature drops below the zone setpoint, minus the zone heating deadband and into the zone heating proportional band, a discharge setpoint is calculated based on a discharge heating low limit and discharge heating reset band. This strategy uses a discharge sensor to control heating and cooling around the calculated discharge setpoint. It controls and sequences the preheat (if selected and sequenced) and heating devices as the discharge temperature decreases below the actual discharge setpoint minus the discharge heating deadband. The discharge sensor also controls the mechanical cooling device as the discharge air temperature increases above the actual discharge setpoint. As discharge temperature varies through the heating and cooling proportional bands, the output to the controlled devices modulate between 0 to 100%. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
8
SPSARZT2
Zone SetpointHeating DeadbandHeating Proportional BandDischarge Heating Low LimitDischarge Heating Reset BandHeating IntegrationCooling Proportional BandDischarge Cooling Low LimitDischarge Cooling Reset BandCooling Integration
Discharge Setpoint
Heating DeadbandHeating Proportional BandPreheat Proportional BandCooling Proportional BandCooling Integration
Discharge LoopPreheat Command
Heating Command
Cooling Command
Zone Loop
1
4
3
2
5
67
1
432
5
6 78
9 10 11 12
10
12 11
9
Figure 10: Supply Air Reset from Zone Temperature
AHU Applications Application Note 20
Mixed Air Dual Path or 100% Outside Air Dual Path Applications
Schematic Figure 11 is a schematic of a dual path application.
SupplyFan
CoolingCoil
HeatingCoil
Hot DeckTemperature
Cold DeckTemperature
N.O.
Supply Air
Zone Control(by separate controller)
N.C.
MADPDUCT
* From PreheatCoil Discharge
* See 100% Outside Air Single Path or Mixed Air Single Path schematic for return/exhaust fan, dampers, and preheat coil.
Figure 11: Dual Path Schematic
Control Strategy The first question in the mixed air dual path or 100% outside air dual path question/answer path (Figures 52 and 53) asks you to select the control strategy. The available strategies are:
• Multizone Hot/Cold Deck Reset
• Dual Duct Hot/Cold Deck Reset
• Multizone Zone Control
• Dual Duct Zone Control The following provides information on each of the four available strategies.
Multizone Hot/Cold Deck Reset or Dual Duct Hot/Cold Deck Reset This control strategy controls typical multizone or dual duct type air handlers (Figure 12). It uses the temperature from the warmest and coldest zone, and calculates a cold deck and hot deck setpoint through a cold and hot deck reset schedule respectively. The cold deck setpoint and the cold deck discharge temperature controls the outdoor air damper (if sequenced with cooling) and mechanical cooling device in sequence. The hot deck setpoint and the hot deck temperature control the heating device. When a preheat device is selected, it will be controlled as a Separate Mixed Air Closed Loop. It is recommended that the preheat setpoint be a value lower than the cold deck low limit.
AHU Applications Application Note 21
DPRHCDR2
Hot Deck ControlColdest Zone High LimitColdest Zone Reset BandHot Deck Low LimitHot Deck Reset BandColdest Zone Temperature
Hot Deck Setpoint
Heating Proportional BandHeating Integration
HotDeck
Cold Deck Setpoint
Cooling Proportional BandCooling Integration
Cold Deck Control
Coldest Zone
Warmest ZoneWarmest Zone High LimitWarmest Zone Reset BandCold Deck Low LimitCold Deck Reset BandWarmest Zone Temperature
5
1
32
4
5
12
4
3
5 6
6
1
32
41
3
2
4
5
6
6
Heating Command
CoolingCommand
Figure 12: Multizone Hot/Cold Deck Reset or Dual Duct Hot/Cold Deck Reset
Reset Schedule The four input parameters of each reset schedule determine the reset schedule for the cold and hot deck. The hot zone high limit, hot zone reset band, cold deck low limit, and cold deck reset band establish the cold deck reset schedule. The system uses the warmest zone temperature to calculate the cold deck setpoint through this reset schedule. The cold zone high limit, cold zone reset band, hot deck low limit and hot deck reset band establish the hot deck reset schedule. The system uses the coldest zone temperature to calculate the hot deck setpoint through this reset schedule. The coolest and warmest zone temperatures are individual analog inputs. Zones that are not the warmest or coolest control their zone damper through separate control loops outside of this sequence.
Cold Deck Control If the system is mixed air dual path, the outdoor air damper and mechanical cooling device are in sequence. As the cold deck temperature rises above the calculated cold deck setpoint and enters the economizer proportional band, the economizer dampers will modulate from minimum position to 100% open (if economizer is enabled). The cold deck cooling deadband is added to the cold deck setpoint and establishes the cold deck temperature value at which the mechanical cooling proportional band begins. An alternate cooling deadband is used when Econ mode is not available. As the cold deck temperature rises through the cold deck proportional band, the mechanical cooling device will modulate from 0 to 100% open. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
AHU Applications Application Note 22
The system controls the outdoor air dampers from minimum position during the Occupied mode and from 0% during the Unoccupied mode. It is possible to eliminate the operation of the outdoor air damper in Unoccupied mode by setting the unoccupied economizer proportional band equal to zero.
Hot Deck Control The system controls the hot deck heating device when the hot deck temperature is below the calculated hot deck setpoint. As the temperature enters the heating proportional band, the output to the controlled device will modulate from 0 to 100% open. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control. Zone Mixing Damper Control For satisfying the load in the space, the system requires zones that are not the warmest or coldest to mix the hot and cold deck air streams. This means that a separate closed loop must exist outside the AHU controller to control each of the zone dampers. Individual zone temperature control may be a pneumatic loop with a T-4002 thermostat controlling the zone damper. The system brings the multiple thermostats into a C-2220 high/low signal selector that selects the zones with the greatest heating and cooling demands. The system brings these signals out of the C-2220 and into two FM-IAP101-0s. The FM-IAP101-0s convert the high and low pneumatic signals into 4 to 20 mA signals that connect into the AHU controller. HVAC PRO can scale this signal internally to the sensitivity range of the T-4002 thermostat.* * Refer to the Appendix D: Multizone Hot and Cold Deck Reset
Application Note in the Appendix section of the HVAC PRO User’s Manual, which explains how to set up the analog inputs for the warmest and coolest zones.
Typically, on digitally controlled zones, a supervisory system like Metasys® Companion/Facilitator or Metasys Network Control Module (NCM) is applied to select the warmest and coolest zones from the zone controllers, and then globally share this data with the AHU.
AHU Applications Application Note 23
Multizone Zone Control or Dual Duct Zone Control This control strategy takes the warmest and coldest zone inputs and directly controls the cold and hot deck respectively (Figure 13). It is appropriate for direct zone control of dual duct and multizone systems.
DPMRZC2
Coldest Zone Temperature (CZ-T)Zone Heating SetpointHeating Proportional BandHeating IntegrationWarmest Zone Temperature (WZ-T)Zone Cooling SetpointCooling Proportional BandCooling Integration
Hot Deck Command
Cold Deck Command
Zone LoopCLGHTG
34
12
2 1 3 4
CZ-T WZ-T
Figure 13: Zone Control
Warmest Zone Control The system controls the outdoor air damper (if selected and sequenced) and mechanical cooling device in sequence. As the warmest zone temperature rises above the calculated warmest zone setpoint and enters the economizer proportional band, the economizer dampers will modulate from minimum position to 100% open (if Econ is enabled). The warmest zone cooling deadband is added to the warmest zone setpoint and establishes the warmest zone temperature value at which the mechanical cooling proportional band begins. An alternate cooling deadband is used when Econ mode is not available. As the warmest zone temperature rises through the warmest zone proportional band, the mechanical cooling device will modulate from 0 to 100% open. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control. The system controls the outdoor air dampers from minimum position during the Occupied mode and from 0% during the Unoccupied mode. It is possible to eliminate the operation of the outdoor air damper by setting the unoccupied economizer proportional band equal to zero.
Coolest Zone Control The system controls the heating device below the calculated coolest zone setpoint. As the coolest zone temperature decreases below the calculated coolest zone setpoint and enters the heating proportional band, the output to the controlled device will modulate from 0 to 100% open. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
AHU Applications Application Note 24
Zone Mixing Damper Control For satisfying the load in the space, the system requires zones that are not the warmest or coldest to mix the hot and cold deck air streams. This means that a separate closed loop must exist outside the AHU controller to control each of the zone dampers. Individual zone temperature control may be a pneumatic loop with a T-4002 thermostat controlling the zone damper. The system brings the multiple thermostats into a C-2220 high/low signal selector that selects the warmest and coldest zones. The system brings the warmest and coldest zone signals out of the C-2220 and into two FM-IAP101-0s. The FM-IAP101-0s convert the high and low pneumatic signals into 4 to 20 mA signals that connect into the AHU controller. HVAC PRO scales this signal internally to the sensitivity range of the T-4002 thermostat.* * Refer to the Appendix D: Multizone Hot and Cold Deck Reset
Application Note in the Appendix section of the HVAC PRO User’s Manual, which explains how to set up the analog inputs for the warmest and coolest zones.
Typically, on digitally controlled zones, a supervisory system like Metasys Companion/Facilitator or Metasys NCM is applied to select the warmest and coolest zones from the zone controllers, and then “globally share” this data with the AHU.
AHU Applications Application Note 25
Heat Recovery for 100% Outside Air Applications
Heat Recovery Type The first question in the heat recovery for 100% outside air applications question/answer path (Figure 54) asks you to select the heat recovery type. The available types are:
• 2-position Output from Analog Input Sensor
• Run Around Glycol Loop The following provides information on each of the available types.
2-Position Output from Analog Input Sensor When the outdoor or discharge air temperature (user selectable via question) decreases below the heat recovery setpoint, a maintained binary output energizes, causing the 2-position heat recovery device (Figure 14) to be on or open. When the temperature increases to a value that is equal to the heat recovery setpoint plus the heat recovery differential, the controller commands the heat recovery device off or closed. If the heat recovery control sensor becomes unreliable, the command to the heat recovery device is off or closed. This control loop must have proven airflow. Whenever the system loses airflow or when the Shutdown mode is on, the system commands the heat recovery device off or closed.
HR2PDifferential
Outdoor Air or Discharge Air Temperature
Heat Recovery Setpoint
NOT
Shutdown
Airflow
00
OR
Compare FailSoft
BOHeat Recovery
Figure 14: Heat Recovery for 2-Position Device
Run Around Glycol Loop When the heat recovery temperature decreases below the heat recovery setpoint and into the heat recovery proportional band, the 3-way valve opens to allow modulated flow between the exhaust and supply coils (Figure 15).
AHU Applications Application Note 26
HR-GL
BO
PI Control
Multiply
Shutdown Airflow
Heat Recovery AO
1.0%Differential 1.0%
Glycol Low Limit
Heat Recovery SetpointProportional Band
IntegrationOffset
DeadbandHeat Recovery AI
0
0
Glycol Low Limit SetpointProportional Band
IntegrationDeadband
Glycol Temperature
Pump Start
ComparePI
12
12
0 - 1
1 2
0
1
12
Figure 15: Run Around Glycol Loop Whenever the glycol temperature decreases below the glycol low limit setpoint, the low limit loop backs off the heat recovery loop causing more flow to the exhaust coil to protect the exhaust coil from condensation and frost. The Shutdown mode or loss of airflow commands the output to the heat recovery valve to 0% open. See Figure 16.
Return
Discharge
Exhaust
Glycol TemperaturePump
Heat RecoveryValve
HeatRecovery
Temperature
Outside N.C.
GLYCOL
N.C.
Figure 16: Heat Recovery Device
AHU Applications Application Note 27
Economizer
Description The system controls the outdoor air dampers from minimum position during the Occupied mode and from 0% during the Unoccupied mode. Through the unoccupied control parameters, you can eliminate outdoor air damper operation during the Unoccupied mode.
ELCAMAS
100%
Vent Airflow Shutdown
100%
Economizer Command
Outdoor Air TemperatureFailSoft
Purge
0
0 Economizer Command AOMinimum Position, 0, or
Last Command
Figure 17: Economizer Logic Common to All Systems
Switchover Strategy The last question in the economizer question/answer path (Figure 55) asks you to select the switchover strategy. The available strategies are:
• None
• Software (N2) Command
• Hardware BI Point
• Dry Bulb
• Enthalpy Comparison
• Outdoor Air Enthalpy
• Fixed Temperature Differential The following provides information on each of the available strategies.
None When you do not select an economizer strategy, the outdoor air damper modulates from minimum position to 100% open to provide cooling without switchover logic intervention. Unless “free cooling” from outside air is available year around, this selection is usually not valid (that is, the outdoor air dampers will open to provide cooling even when the outdoor air has a high heat content).
AHU Applications Application Note 28
Software (N2) Command A binary data point is generated for a Facility Management System (FMS) to command (Figure 18). One controller can determine economizer changeover logic and report it to the FMS which can then distribute the information to the other controllers on the network through their binary data points. When economizer is commanded on, free cooling is available.
ELN2C
N2 Command(ECON)
Minimum Position
Control Command From Sequencer
ECON
Figure 18: Software (N2) Command
Hardware BI Point A binary input is used to read the output from an outdoor air temperature switch (Figure 19). When the switch closes (BI is On), the economizer status is off; when the switch opens (BI is Off), the economizer status is on. When economizer status is on, free cooling is available.
EBI
NOTBIECON
ECON
Figure 19: Hardware BI Point
Dry Bulb The outdoor air temperature is compared to an economizer switchover setpoint to determine economizer status (Figure 20). The economizer status is off when the outdoor air temperature exceeds the switchover setpoint. When the outdoor air temperature is less than the switchover setpoint minus a two degree differential, economizer status is on. If the outdoor air sensor is unreliable, economizer status is off. When economizer status is on, free cooling is available.
EDBS
Switchover DifferentialECON
Outdoor Air Temperature CompareSwitchover Setpoint
Figure 20: Dry Bulb Switchover
AHU Applications Application Note 29
Enthalpy Comparison Return air temperature and humidity are used to calculate the return air enthalpy (Figure 21). Outdoor air temperature and humidity are used for calculating outdoor air enthalpy which is then compared to the return air enthalpy. When the outdoor air enthalpy exceeds the return air enthalpy, or the outdoor air temperature exceeds the dry bulb default, economizer status is off. When the outdoor air enthalpy is less than the return air enthalpy minus the enthalpy differential switchover and the outdoor air temperature is less than the dry bulb default minus a two degree differential, economizer status is on. If either the return temperature or return humidity becomes unreliable, the outdoor air enthalpy is compared to a failsoft enthalpy of 30 Btu/lb. If the outdoor air humidity sensor becomes unreliable, the outdoor air temperature is compared to the default economizer setpoint. If the outdoor air temperature sensor becomes unreliable, the economizer status is off. When the economizer status is on, free cooling is available.
EC
Outdoor Air Temperature
Outdoor Air RH
EnthalpyCalculation
Outdoor Air Temperature Compare
NOTORCompare
12
1 2ECON
EnthalpyDifferential
Economizer SwitchoverDry Bulb Setpoint
(Default)
EnthalpyCalculation
Return Air Temperature
Return Air RH
Figure 21: Enthalpy Comparison
AHU Applications Application Note 30
Outdoor Air Enthalpy Outdoor air temperature and humidity are used to calculate outdoor air enthalpy for comparison to an enthalpy switchover setpoint (Figure 22). If the outdoor air enthalpy exceeds the enthalpy switchover setpoint, or if the outdoor air temperature exceeds the default economizer setpoint, economizer status is off. When the outdoor air enthalpy is below the enthalpy switchover setpoint minus a differential of one Btu/lb, and if the outdoor air temperature is below the default economizer setpoint default minus a two degree differential, the economizer status is on. If the humidity sensor is unreliable, then the controller uses only the default economizer setpoint to determine economizer status. If the outdoor air sensor becomes unreliable, the economizer status is off. When economizer status is on, free cooling is available.
EOAES
Differential
Outdoor Air Temperature
Outdoor Air RH
EnthalpyCalculation
Outdoor Enthalpy Setpoint
Outdoor Air TemperatureEconomizer Switchover
Dry Bulb Setpoint
Compare
NOTORCompare
12
1 2ECON
Figure 22: Outdoor Air Enthalpy
Fixed Temperature Differential The outdoor air temperature is subtracted from the return air temperature and compared to the temperature differential switchover (Figure 23). Economizer status is off when the difference between the temperatures is less than the temperature differential switchover. When the difference between the temperatures exceeds the temperature differential switchover plus a two degree differential, the economizer status is on. If either the outdoor air or return air sensors becomes unreliable, economizer status will be off. When economizer status is on, free cooling is available.
EFTD
Return Temperature
Outdoor Temperature
Subtract
Economizer Switchover Differential
SetpointDifferential = 2.0
Compare NOT ECON
Figure 23: Fixed Temperature Differential
AHU Applications Application Note 31
Preheat
Device Type The first question in the preheat question/answer path (Figure 61) asks you to select the preheat device type. The available types are:
• 2 Position Steam/Water Valve (Sensor Cntl’d)
• Face and Bypass w/Vlv Switch over Seq w/Htg Clg
• Modulated Single Coil
• Staged The following provides information on each of the available types.
2 Position Steam/Water Valve (Sensor Cntl’d) When the outdoor, mixed, or discharge temperature (user selected) falls below the preheat low limit setpoint, the controller commands a binary output to on (Figure 24). When the temperature rises above the preheat low limit setpoint plus the preheat low limit differential, the controller commands the binary output to off. Airflow interlock is optional in this control loop.
AHU Applications Application Note 32
PC2PV
Airflow Interlock (BI)or
Remain in Control (1)
(Preheat Lockout)
0%100%
Purge
Vent
NOTBOPreheat
Shutdown
Differential
AND
Compare
Outdoor Air Temperature
Loss of Airflow Choice0% = 0
100% = 1Remain in Control = 1
0, 1
0
NOT
AND
Compare
FailSoft
AND
AND
NOT
OR
AND OR
AIPreheat Low Limit
Setpoint Differential
Figure 24: 2-Position Steam/Water Valve
Face and Bypass w/Vlv Switch over Seq w/Htg Clg This control strategy is part of the main control strategy selected at the beginning of HVAC PRO (Figure 25). The discharge air or zone temperature controls this loop depending on your selection. When the outdoor air temperature is below the outdoor air face and bypass switchover setpoint, the controller commands the preheat valve to 100% open, while it modulates the face and bypass damper. As the control temperature falls through the preheat proportional band, the damper shall modulate from bypass (0%) to face (100%). When the outdoor air temperature rises above the outdoor air face and bypass switchover setpoint plus the outdoor temperature face/bypass differential setpoint, the controller commands the face damper to 100% face and modulates the preheat valve to obtain the control setpoint.
AHU Applications Application Note 33
PCFB
.cdr
100%
Pump Start
100%
Vent Airflow
Shutdown
BO
Airflow Shutdown
FailSoft
AO Preheat Valve
CompareOutdoor TemperatureFace and Bypass
Switch Setpoint
Preheat Command
FailSoft
Purge
0
OutdoorTemperature
0
(Lockout)
Compare
AO Face and Bypass
Compare00
SetpointOutdoor Temperature
Differential
0, 100, orRemain in
Control
0, 100, orRemain in
Control
0, 100, orRemain in
Control
0, 100, orRemain in
Control
0, 100, orLast Reliable
Command
0, 100, orLast Reliable
Command
Figure 25: Face and Bypass with Valve Switchover
AHU Applications Application Note 34
The preheat proportional band allows the sequence of preheat operation as the control temperature decreases below the control setpoint. A heating device can be sequenced and controlled as the control temperature continues to decrease below the preheat band. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control. The integration term for this control loop is shared with the sequenced heating device. This option is not valid for Dual Path units.
Modulated Single Coil This strategy allows the preheat device to be controlled as an independent loop or as part of the main control strategy (Figure 26). The preheat proportional band allows the sequence of preheat operation as the control temperature decreases below the control setpoint. A heating device can be sequenced and controlled as the control temperature continues to decrease below the preheat proportional band. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control. The integration term for this control loop is shared with the sequenced heating device.
PMSC2
PI
Outdoor TemperatureSetpoint
Differential
Purge Vent Airflow
Shutdown
AOPreheat
BOPump
Preheat SetpointProportional Band
IntegrationOffset
Deadband
Mixed Air Temperature (Rev 1.0)Separate Sensor (Rev 2.0)
or
Preheat Command
FailSoft
0, 100, orLast Reliable
Command
0
0
0
0
00
Compare
Compare
12
12
Figure 26: Modulated Single Coil
AHU Applications Application Note 35
Staged This strategy allows electric preheat stages to be controlled as an independent loop or as part of the main control strategy (Figure 27). The preheat stages energize as the control temperature decreases into the preheat proportional band. It can be sequenced with a preheat device if selected. Adding integration to a control loop with staged outputs is not advised, as it usually results in the constant cycling of the outputs. Staged outputs are airflow interlocked. The integration for this loop is shared with the sequenced heating device.
PS2
Preheat SetpointProportional Band
IntegrationOffset
Deadband
Mixed Air Temperature (Rev 1.0)Separate Sensor (Rev 2.0)
Purge
Outdoor Temperature
Lockout Setpoint
Differential
Vent
Compare
Airflow
Preheat Command
or
Shutdown
0, 100, orRemain in
Control
00
0 0
FailSoft
BOSequencer
Timers
1234
12
1
2
>
Figure 27: Staged
Sequencer - Number of Stages The minimum on/off and interstage on/off timers can be adjusted once for all stages or for each individual stage. Once it is on, the minimum on timer keeps a stage energized for a minimum time period. Once it is off, the minimum off timer does not allow a stage to be re-energized for a minimum time period. The interstage delay on and off timers prevent the next stage from energizing or de-energizing until the interstage timer has expired. The interstage on timer for Stage 1 controls the elapsed time before Stage 2 may be turned on. The interstage timer for Stage 2 must elapse before Stage 3 may be turned on, and so on. The reverse is true for the interstage off timers. The interstage on of the last stage has no effect, and the interstage off of the first stage has no effect.
AHU Applications Application Note 36
Use the cycles per hour adjustment to restrict the unit from over cycling by providing a minimum time between starts. The cycle per hour feature divides a one hour period into equal cycle intervals. A value of six divides a one hour period into six, 10-minute intervals. Once a stage is commanded on, ten minutes must elapse before another on command is issued. Once a stage is turned off, it cannot be turned on again until the cycle per hour interval and minimum off timer are satisfied. The starting point of the first stage can be adjusted to any value that is 5% or greater and less than the starting point of the second stage. The command and starting point of each stage is based on the 0 to 100% command into the sequencer, with the proportional division of the number of stages over a 0 to 100% range. When you select the first stage to start at 0%, the starting point of the first stage defaults to the normal proportional division (that is, 3 stages would start at 33, 67, and 100% commands). You can override the preheat stages by commanding the pseudo-analog output for preheat. This ensures a 0 to 100% override value is used, keeping the timers inside the sequencing logic active. Individual binary outputs are not eligible to be overridden when part of a sequencer.
IMPORTANT: Staged outputs remain on for their defined minimum on time, regardless of their commanded state.
When all stages must be turned off without delay, adjust the interstage off time to 0. The minimum on timer can hold a stage on even though the Shutdown mode or airflow interlock is active. Keep minimum on timers at the smallest possible value or 0. AHU controllers with C06 firmware or later and UNT (Unitary) controllers with B00 firmware or later will utilize an Instant Off feature. This feature will force all staged outputs off on loss of airflow or shutdown regardless of timer conditions.
AHU Applications Application Note 37
Heating
Device Type The first question in the heating question/answer path (Figure 64) asks you to select the heating device type. The available types are:
• Modulated Single Coil
• Modulated Common Htg and Clg Coil
• Staged
• 2-Position Valve w/Face and Bypass
• Position Adjust - Incremental The following provides information on each of the available types.
Modulated Single Coil The system controls the modulated single heating coil through the main control sequence of operation (Figure 28). The controller sequences the operation of the heating coil with preheat (if selected and sequenced) and cooling. The heating valve will modulate as the control temperature decreases below the control setpoint and into the heating proportional band. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
ABO1A
SoftHeating
Command
Purge Vent Airflow Shutdown
AO
Pump Start
BO0
0
0
00, 100, or
Last Reliable Command
0
Compare
Heating LockoutSee Lockout illustration. (Figure 29)
Fail
Figure 28: Modulated Single Coil Heating
AHU Applications Application Note 38
HeatingLockout
N2 Command
Outdoor Air TemperatureHeating Lockout Setpoint
Differential
Compare
HeatingLockout
Outdoor Air TemperatureHeating Lockout Setpoint
Differential
Compare
N2 Command withAI Backup
AI Switch
N2 Command Status
N2 Command
HeatingLockout
CommandLOCKOUT
Figure 29: Lockout
Modulated Common Htg and Clg Coil The common heating and cooling coil is controlled through the main sequence of operation (Figure 30). During the Winter mode of operation (sum/win = on), the controller shall modulate the valve from fully closed to open as the control temperature decreases below the control setpoint and passes through the heating proportional band (Figure 31). The heating signal shall be sequenced with preheat (if selected and sequenced). During the Summer mode of operation (sum/win = off), the controller shall modulate the valve from fully closed to open as the control temperature increases above the control setpoint and passes through the cooling proportional band. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
AHU Applications Application Note 39
ABO2
SoftHeating Command
Purge Vent Airflow Shutdown
AOCooling
Command
AISetpoint
Differential
BO
orSUM / WIN(N2 or BI)
0
0
0
0
00, 100, or
Last Reliable Command
Pump Start
Compare
CompareHeating and Cooling Lockout
See Lockout illustrations.(Figures 29 and 35)
Fail
Figure 30: Modulated Common Heating and Cooling Coil
HeatingHigh SetpointDifferential
Heating/Cooling Sensor
Winter Mode
Summer ModeAHUSUMWI
Figure 31: Summer/Winter Switchover
Staged This strategy allows electric heating stages to be controlled as part of the main control strategy (Figure 32). The heating stages energize as the control temperature decreases into the heating proportional band. It can be sequenced with a preheat device if selected. Adding integration to a control loop with staged outputs is not advised, as it usually results in the constant cycling of the outputs.
AHU Applications Application Note 40
ABO3
Airflow ShutdownVentPurge
0
0
0
0
0
BOFace and Bypass
Compare
Heating Command
0, 100, orLast Reliable Command
BOSequencer
Timers
1234
AOVernier Control
Heating LockoutSee Lockout illustration. (Figure 29)
FailSoft
Figure 32: Staged Heating
2-Position Valve w/Face and Bypass The heating command from the main control sequence modulates a face and bypass damper as the control temperature decreases into the heating proportional band (Figure 33). A 2-position command will open a heating valve when the heating command increases above a user adjustable setpoint. This output has adjustable minimum on and off timers. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
ABO3A
FailSoft
Airflow ShutdownVentPurge
Heating Command
0
0
0
0
00, 100, or
Last Reliable Command
Compare
AOFace and Bypass
BOValve
Heating LockoutSee Lockout illustration. (Figure 29)
Figure 33: 2-Position Valve with Face and Bypass
Position Adjust – Incremental The controller uses two binary outputs to position the control valve. The stroke time you specify determines the timing of these binary outputs. The controller uses the zone temperature to determine the required position of the valve. Then it energizes the appropriate output for a percent of full stroke to achieve the required valve position.
AHU Applications Application Note 41
As the zone temperature drops below the heating setpoint, the controller energizes the appropriate output to open the valve. As the zone temperature increases, the controller energizes the other output to close the valve. When the temperature is within the deadband of the controller, neither output is energized and the valve stays in its current position. As the required position drops below the current position, the controller energizes the appropriate output to close the valve. As the required position increases, the controller energizes the other output to open the valve. When the change from the current position to the calculated new position is within the controller’s deadband, neither output is energized, leaving the valve in its current position. The controller uses overdrive logic to ensure the position of the valve. When the output reaches 99%, it will be driven for 1.5 times the stroke time, causing the valve to reach its 100% position.
Sequencer - Number of Stages You can adjust the minimum on/off and interstage on/off timers once for all stages or for each individual stage. Once it is turned on, the minimum on timer keeps a stage energized for the input time period. The minimum off timer does not allow a stage to be re-energized for a time period once it is turned off. The interstage delay on and off timers prevent the next stage from energizing or de-energizing until the interstage timer has expired. The interstage on timer for Stage 1 controls the elapsed time before Stage 2 may be turned on. The interstage timer for Stage 2 must elapse before Stage 3 may be turned on, and so on. The reverse is true for the interstage off timers. The interstage on of the last stage has no effect, and the interstage off of the first stage has no effect. Use the cycles per hour adjustment to restrict the unit from over cycling by providing a minimum time between starts. The cycle per hour feature divides a one hour period into equal cycle intervals. A value of six divides a one hour period into six 10-minute intervals. Once a stage is turned on, ten minutes must elapse before another on command is issued. Once a stage is turned off, it cannot be turned on again until the cycle per hour interval and minimum off timer is satisfied.
AHU Applications Application Note 42
The starting point of the first stage can be adjusted to any value that is 5% or greater and less than the starting point of the second stage. When you answer this question 0%, the stages are automatically proportioned over the heating proportional band. The command and starting point of each stage is based on the 0 to 100% command into the sequencer, with the proportional division of the number of stages over a 0 to 100% range. When you select the first stage to start at 0%, the starting point of the first stage defaults to the normal proportional division (i.e., 3 stages would start at 33, 67, and 100% commands). You can override the heating stages by commanding the pseudo-analog output for heating. This ensures a 0 to 100% override value is used, keeping the timers inside the sequencing logic active. Individual binary outputs are not eligible to be overridden when part of a sequencer.
IMPORTANT: Staged outputs remain on for their defined minimum on time, regardless of their commanded state.
When all stages must be turned off without delay, adjust the interstage off time to 0. The minimum on timer can hold a stage on even though the Shutdown mode or airflow interlock is active. Keep minimum on timers at the smallest possible value or 0. AHU controllers with C06 firmware or later and UNT controllers with B00 firmware or later will utilize an Instant Off feature. This feature will force all staged outputs off on loss of airflow or shutdown regardless of timer conditions.
Cooling
Device Type The first question in the cooling question/answer path (Figure 68) asks you to select the cooling device type. The available types are:
• Modulated Single Coil
• Staged
• 2-Position Valve w/Face and Bypass
• Position Adjust - Incremental The following provides information on each of the available types.
AHU Applications Application Note 43
Modulated Single Coil The system controls the modulated single cooling coil through the main control sequence (Figure 34). The controller sequences operation of the cooling coil with heating and outdoor air damper operation (if sequenced). As the control temperature increases above the zone or discharge setpoint, through the cooling deadband and into the cooling proportional band, the controller issues a 0 to 100% command to the cooling device. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
ABO4A
Vent Airflow Shutdown
AO
DehumidificationLogic
CoolingCommand
00
0
0
0
FailSoft
BOPump Start
0, 100, or Last Reliable Command
Compare
See the
section.
Cooling LockoutSee Lockout illustration. (Figure 35)
Purge
Dehumidification
Figure 34: Modulated Single Coil Cooling
CoolingLockout
N2 Command
Outdoor Air TemperatureCooling Lockout Setpoint
Differential
Compare
CoolingLockout
Outdoor Air TemperatureCooling Lockout Setpoint
Differential
Compare
N2 Command withAI Backup
AI Switch
N2 Command Status
N2 Command
CoolingLockout
Command
CLGLOCK
Figure 35: Lockout
AHU Applications Application Note 44
Staged This strategy allows Direct Expansion (DX) cooling stages to be controlled as part of the main control strategy (Figure 36). The controller sequences the DX stages as the control temperature increases into the cooling proportional band. Adding integration to a control loop with staged outputs is not advised as it usually results in the constant cycling of the outputs.
ABO4B
FailSoft
Purge Vent Airflow Shutdown
DehumidificationLogic
CoolingCommand
0 0 0
0
0, 100, orRemain in Control
BOSequencer
Timers
1234
AOVernier Control
Cooling LockoutSee Lockout illustration. (Figure 35)
See theDehumidification
section.
Figure 36: Staged Cooling
2-Position Valve w/Face and Bypass The cooling command from the main control sequence modulates a face and bypass damper as the control temperature increases into the cooling proportional band. A 2-position command will open a cooling valve when the cooling command increases above a user adjustable setpoint. This output has adjustable minimum on and off timers. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
Position Adjust – Incremental The controller uses two binary outputs to position the control valve. The timing of these outputs is based on an operator specified stroke time. The controller uses the zone temperature to determine the required position of the valve. Then the controller will cause the appropriate output to energize for a percent of full stroke to achieve the required valve position. As the zone temperature rises above the cooling setpoint, the controller energizes the appropriate output to open the valve. As the zone temperature decreases, the controller energizes the other output to close the valve. When the temperature is within the deadband of the controller neither output energizes, leaving the valve in its current position. The controller uses overdrive logic to ensure the position of the valve. When the output reaches 99%, it will be driven for 1.5 times the stroke time, causing the valve to reach its 100% position.
AHU Applications Application Note 45
Sequencer - Number of Stages The minimum on/off and interstage on/off timers can be adjusted once for all stages or for each individual stage. Once turned on, the minimum on timer keeps a stage energized for the input time period. Once turned off, the minimum off timer does not allow a stage to re-energize for the input time period. The interstage delay on and off timers prevent the next stage from energizing or de-energizing until the interstage timer has expired. The interstage on timer for Stage 1 controls the elapsed time before Stage 2 may be turned on. The interstage timer for Stage 2 must elapse before Stage 3 may be turned on, and so on. The reverse is true for the interstage off timers. The interstage on of the last stage has no effect, and the interstage off of the first stage has no effect. Use the cycles per hour adjustment to restrict the unit from over cycling by providing a minimum time between starts. The cycle per hour feature divides a one hour period into equal cycle intervals. A value of six divides a one hour period into six 10-minute intervals. Once a stage is turned on, ten minutes must elapse before another on command can be issued. Once a stage is turned off, it cannot be turned on again until the cycle per hour interval and minimum off timer is satisfied.
ABO4C
FailSoft
Purge Vent Airflow Shutdown
DehumidificationLogic
CoolingCommand
AOFace and Bypass
0 0
0
00, 100, or
Last Reliable Command
0BO
Cooling Valve
Compare
Cooling LockoutSee Lockout illustration. (Figure 35)
See theDehumidification
section.
Figure 37: Rotational Sequencing of Cooling
AHU Applications Application Note 46
The starting point of the first stage can be adjusted to any value that is 5% or greater and less than the starting point of the second stage. The command and starting point of each stage is based on the 0 to 100% command into the sequencer, with the proportional division of the number of stages over a 0 to 100% range. When you select the first stage to start at 0%, the starting point of the first stage defaults to the normal proportional division (that is, 3 stages would start at 33, 67, and 100% commands). You can override the DX stages by commanding the pseudo-analog output for cooling. This ensures a 0 to 100% override value is used, keeping the timers inside the sequencing logic active. Individual binary outputs are not eligible to be overridden when part of a sequencer.
IMPORTANT: Staged outputs remain on for their defined minimum on time, regardless of their commanded state.
When all stages must be turned off without delay, adjust the interstage off time to 0. The minimum on timer can hold a stage on even though the Shutdown mode or airflow interlock is active. Keep minimum on timers at the smallest possible value or 0. AHU controllers with C06 firmware or later and UNT controllers with B00 firmware or later will utilize an Instant Off feature. This feature will force all staged outputs off on loss of airflow or shutdown regardless of timer conditions.
AHU Applications Application Note 47
Dehumidification
Control Strategy The first question in the dehumidification question/answer path (Figure 70) asks you to select the control strategy. The available strategies are:
• High Signal Selection w/Cooling Command
• Addition of Dehumid. and Cooling Command The following provides information on each of the available strategies.
High Signal Selection w/Cooling Command This control strategy selects the highest signal between the sensible cooling command and the dehumidification command, then outputs the selected value to the cooling device (Figure 38). The cooling command originates from the main temperature control sequence of operation. When the relative humidity increases above the humidity setpoint and into the dehumidification proportional band, a dehumidification command is determined. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
ABO5
SoftMaximum
Select
Dehumidification SetpointProportional Band
IntegrationDeadband
Humidity AIOffset
0
Integration
Airflow
PI 0
Go ToCoolingLogic
1 orOccupied
1 2 0 orLast Command
12
CoolingCommand
Fail
Figure 38: High Signal Selection with Cooling Command
Addition of Dehumidification and Cooling Command This control strategy adds the sensible cooling command from the main sequence of operation to the dehumidification command and outputs the total value to the cooling device (Figure 39). The cooling command originates from the main temperature control sequence of operation. When the relative humidity increases above the humidity setpoint and into the dehumidification proportional band, a dehumidification command is determined. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
AHU Applications Application Note 48
ABO5A
FailSoft
Dehumidification SetpointProportional Band
IntegrationDeadband
Humidity AIOffset
Integration
Airflow
Go ToCoolingLogic
100.0
PI
ADDMinimum
Select
0
0
1 orOccupied
12
21 0 orLast Command
CoolingCommand
Figure 39: Addition of Dehumidification and Cooling Command
AHU Applications Application Note 49
Humidification
Description A humidity high limit device is recommended with any humidification strategy. The device should be located in the supply duct, at least eight feet downstream of the humidifier. A device such as the HLC-1000 can be used to limit the electronic signal to the humidifier from the controllers analog output when a high limit setpoint is reached.
Sequencer - Number of Stages The minimum on/off and interstage on/off timers can be adjusted once for all stages or for each individual stage. Once turned on, the minimum on timer keeps a stage energized for the input time period. Once turned off, the minimum off timer does not allow a stage to re-energize for the input time period. The interstage delay on and off timers prevent the next stage from energizing or de-energizing until the interstage timer has expired. The interstage on timer for Stage 1 controls the elapsed time before Stage 2 may be turned on. The interstage timer for Stage 2 must elapse before Stage 3 may be turned on, and so on. The reverse is true for the interstage off timers. The interstage on of the last stage has no effect, and the interstage off of the first stage has no effect. Use the cycles per hour adjustment to restrict the unit from over cycling by providing a minimum time between starts. The cycle per hour feature divides a one hour period into equal cycle intervals. A value of six divides a one hour period into six 10-minute intervals. Once a stage is turned on, ten minutes must elapse before another on command can be issued. Once a stage is turned off, it cannot be turned on again until the cycle per hour interval and minimum off timer is satisfied. The command and starting point of each stage is based on the 0 to 100% command into the sequencer, with the proportional division of the number of stages over a 0 to 100% range (i.e., 3 stages would start at 33, 67, and 100% commands). You can override the humidity stages by commanding the pseudo-analog output for humidity. This ensures a 0 to 100% override value is used, keeping the timers inside the sequencing logic active. Individual binary outputs are not eligible to be overridden when part of a sequencer.
IMPORTANT: Staged outputs remain on for their defined minimum on time, regardless of their commanded state.
AHU Applications Application Note 50
When all stages must be turned off without delay, adjust the interstage off time to 0. The minimum on timer can hold a stage on even though the Shutdown mode or airflow interlock is active. Keep minimum on timers at the smallest possible value or 0. AHU controllers with C06 firmware or later and UNT controllers with B00 firmware or later will utilize an Instant Off feature. This feature will force all staged outputs off on loss of airflow or shutdown regardless of timer conditions.
AHU Applications Application Note 51
Modes of Operation
Unoccupied Control Strategy Note: When occupied is on, the controller assumes the occupied
setpoints and operates as normal.
The first question in the modes of operation question/answer path (Figure 73) asks you to select the control strategy. The available strategies are:
• Intermittent Night Operation from Zone Sensor
• Setup/Setback of Htg/Clg Setpts in Main Seq Operation from Zone (Only in Room Control Strategy)
The following provides information on each of the available strategies.
Intermittent Night Operation from Zone Sensor The intermittent night operation selection is a valid option for all the AHU control strategies including:
• Room Control
• Return Air Control
• Constant Discharge Air Control
• Supply Air Reset from Return/Exhaust
• Room Control of Cooling/Room Reset of Heating
• Supply Air Reset from Zone This selection requires a zone sensor which will only be used for night operation. When the controller is in the Unoccupied mode and the zone temperature is above the night cooling or below the night heating setpoint, the unit will start (Figure 40).
AHU Applications Application Note 52
BO9
XOROccupied
Warmup/Cooldown
Two Minutes
15 Seconds
BOSupply Fan
Zone TemperatureNight Heating
SetpointDifferential
Zone TemperatureNight Cooling
SetpointDifferential
Shutdown
Supply Air Flow
NOT AND AND
OR OR
DelayOn
DelayOff
AND
NOT
OR
Compare
Compare
Figure 40: Intermittent Night Operation: Supply Fan Start The system controls the control temperature around the occupied heating and cooling setpoints. When the constant discharge air control strategy is selected, user adjustable unoccupied discharge heating and cooling setpoints are used. When the system commands the fan on due to zone temperature, the appropriate discharge temperature is delivered to the zone. The controller commands the fan system off when the zone temperature increases above the night heating setpoint plus the night heating differential, or below the night cooling setpoint minus the night cooling differential. If the mixed air dampers are sequenced with cooling, you may want to prevent free cooling in the Unoccupied mode by setting the unoccupied economizer proportional band to 0. When the economizer status is not on, the mechanical cooling algorithm operates with the alternate cooling deadband (default = 0). This moves the starting point of mechanical cooling to the control setpoint.
AHU Applications Application Note 53
BO9A
Shutdown BOSupply Fan
Zone TemperatureNight Heating
SetpointDifferential
Zone TemperatureNight Cooling
SetpointDifferential
XOR
Return Air Flow15 Seconds
BOReturn FanFan
Delay
Occupied
Warmup/Cooldown
NOT
OR OR
AND
Supply Air Flow15 Seconds
Fan Delay Between
FansAND
DelayOff
DelayOff
DelayOn
AND
AND
NOT
DelayOn
AND
OR
Compare
Compare
Figure 41: Intermittent Night Operation: Supply and Return Fan Start
Setup/Setback of Htg/Clg Setpts in Main Seq Operation from Zone (Only in Room Control Strategy) The setup and setback option is only available when the main control strategy is room control. The controller adds the setup value to the zone cooling setpoint and subtracts the setback value from the zone or heating setpoint. The controller does not use the heating deadband when calculating the setback value. The setback value replaces the heating deadband. The unit fans will start when the preheat (if selected and sequenced), heating, economizer (if selected and sequenced) or cooling proportional command reaches 10% and the unit will stop when the commands have decreased to 1%. Once the unit fan starts and airflow status is on, the command is passed through to the appropriate heating or cooling device. It is likely that once the unit starts in the Setup/Setback mode, it will continue to run for the rest of the unoccupied period while maintaining the setup or setback setpoint. See Figures 42 through 44.
AHU Applications Application Note 54
ABO7
ADD
Warmup/Cooldown
Warmup/Cooldown
Occupied
ZoneSetpoint
Occupied
Go toMain Control Strategy
(Zone Setpoint)
Setup
Setback
0 0
ADD
Go toMain Control Strategy(Heating Deadband)
HeatingDeadband
Figure 42: Setup and Setback: Setpoint Logic
ABO7A
Zone Heating Command 10%
Shutdown
Occupied
NOT
Zone Economizer Command 10%
Zone Preheat Command 10%
Airflow15 Seconds
Zone Cooling Command 10%
DelayOn
DelayOff
2 Minutes
BOSupply Fan
XOR
Compare
Compare
Compare
Compare
OR
OR
OR
OR
AND
NOT AND
AND
Figure 43: Setup and Setback: Single Supply Fan
AHU Applications Application Note 55
BO8
Supply Air Flow
15 Seconds
15 Seconds
Return Air Flow
XOR
Shutdown
Occupied
Fan DelayBetween Fans
2 Minutes
Fan DelayBO
Return Fan
ADD
DelayOn
DelayOff
DelayOff
DelayOn
BOSupply Fan
Same Logic asSingle Supply Fan
Logic
NOT
OR
AND
AND AND
NOT AND
Figure 44: Setup and Setback: Supply and Return Fan Logic
If the mixed air dampers are sequenced with cooling, you may want to prevent free cooling in the Unoccupied mode by setting the unoccupied economizer proportional band to 0. When the economizer status is not on, the mechanical cooling algorithm operates with the alternate cooling deadband (default = 0). This moves the starting point of mechanical cooling to the control setpoint value plus the setup value.
Shutdown Mode The default of the Shutdown mode (Figure 45) is off. When shutdown is enabled, all outputs to fans are turned off, outside air dampers are closed, and the humidity devices are shutdown. Preheat, heating, and cooling outputs will be shutdown to 0% command if the user specified they be affected by shutdown. Otherwise, they will go to their loss of airflow position. In Shutdown mode, all integration timers are set to 0, so no windup occurs when the system is put back into control.
AHU Applications Application Note 56
B010A
N2 Command StatusZone Bus Communication Status
Default Shutdown Start
Default Shutdown Stop
N2 ShutdownCommand
ShutdownCommand
TimeSchedule
Start/Stop
OR
Figure 45: Shutdown Mode
Warmup/Cooldown Mode The Warmup/Cooldown mode is only available if an unoccupied strategy is selected and may only operate in the Unoccupied mode. When commanded on, the Warmup/Cooldown mode stops the unoccupied temperature control strategy selected and starts the fan system if it is not running. It then controls to the temperature setpoints selected for occupied operation. On mixed air systems, if free cooling is available, the mixed air dampers shall modulate from 0 to 100% open, ignoring the minimum outside air position. As the control temperature approaches the control setpoint, the system modulates or stages the controlled devices (preheat, heating, cooling). When the controller switches into Occupied mode, warmup/cooldown ends. This allows the minimum outdoor air dampers to open. Even though Warmup mode ends, it remains on until commanded off. When the Occupied mode is turned off, but the warmup/cooldown is left on, Warmup/Cooldown mode will operate until commanded off. If you selected the constant discharge air control strategy, an unoccupied discharge air setpoint is used until the zone temperature achieves the warmup/cooldown zone setpoint. If the zone temperature is below the warmup/cooldown zone setpoint, the unoccupied heating discharge air setpoint shall be used. If the zone temperature is above the warmup/cooldown zone setpoint, the unoccupied cooling discharge air setpoint shall be used. Once the zone temperature reaches the warmup/cooldown zone setpoint, the discharge air will control to the (occupied) discharge air setpoint. The warmup/cooldown zone differential is used to prevent switching back to the unoccupied discharge air setpoints once the warmup/cooldown zone setpoint is achieved.
AHU Applications Application Note 57
Airflow Interlock and Alarm An airflow switch is incorporated into the controller operation. A two minute delay is in effect after a command to start the fan is sent, allowing time to prove airflow. Airflow must be proven in order to operate the economizer output. If loss of airflow is detected for more than 15 seconds, the preheat, heating, and cooling outputs will be commanded to the user selected loss of airflow output and a fan alarm indication will be given. If you select a return fan, return airflow must be proven for normal operation. In the Fan System Control section, a Fan Commanded Off Upon Loss of Air Flow question is asked. If you answer no, a loss of airflow will not shut down the fan system. Once airflow is in alarm, the airflow status must toggle from off to on to clear the alarm.
Default Schedule When you initiate Occupied mode and shutdown through the software (N2) command only, you can input a default occupied and shutdown start/stop time schedule. This schedule is in effect whenever the N2 Bus is offline longer than ten minutes. The time clock that operates inside the AHU controller is not battery backed. It resets to 00:00 whenever you apply power to the controller or the controller goes through a reset condition, such as when downloaded.
B010
N2 Command StatusZone Bus Communication Status
Default Occupied Start
Default Occupied Stop
OccupiedCommand
TimeSchedule
Start/Stop
OR
N2 OccupiedCommand
Figure 46: Default Schedule The only way to set the controller’s time clock to any time other than 00:00 is through the NCM or Companion/Facilitator via the N2 Bus, or a Zone Terminal (ZT) configured with a weekly schedule for that controller. Whenever you connect a laptop to the Zone Bus (but not a ZT), the controller enters the Service mode. The Service mode disconnects the AHU controller from the N2 Bus. The Occupied mode can be overridden from the Commissioning program of HVAC PRO when you connect the laptop to the Zone Bus (or N2 Bus).
AHU Applications Application Note 58
Fan System
Control Type The first question in the fan system control question/answer path (Figure 75) asks you to select the fan system control type. The available types are:
• Single Supply Fan with Static Press. Cntl.
• Single Sup/Ret Vol Match w/Static Pres Cntl
• Single Supply, Low/High Speed Control
• Constant Volume The following provides information on each of the available types.
Single Supply Fan with Static Press. Cntl. Supply fan output is the trigger for static pressure control. Supply fan status enables the integration term. If the ramp control is not used, the proportional output must be sufficient to make the fan status. This control strategy allows the control of variable frequency/speed drives, inlet vanes or discharge dampers that control static pressure within the air handling system. The static pressure setpoint is in inches of Water Gauge (WG) or Pascals for metric units. The static pressure proportional band, integration value, and derivative weight determine the gain of the control loop. An integration value is always recommended to eliminate the proportional offset in this control loop, as precise static pressure control is required in most cases. Usually derivative control action is not necessary, and the derivative weight should be input as 0. The system adds the static pressure offset value to the PID control calculation and usually remains at 0. The static pressure deadband value establishes a range above and below the static pressure setpoint where the error is considered 0. The deadband is applied above and below the static pressure setpoint. If the static sensor becomes unreliable, the command to the static pressure control device equals 0%.
AHU Applications Application Note 59
NORAMP
AOSupply FanControl
000
Static Pressure
StaticIntegrationTerm
FailSoft
0
MINSelect
Static Pressure 1Static Pressure 2
Supply Fan Cmd
XORANDDelayON
Supply FanCommand
DelayOFF
SupplyAirflow
Process VariableSetpoint
Proportional BandIntegrationDerivative
OffsetDeadband
Figure 47: Single Supply Fan, Static Pressure, without Ramp Control
Single Sup/Ret Vol Match w/Static Pres Cntl Supply fan output is the trigger for static pressure control. Supply fan status enables the integration term. If the ramp control is not used, the proportional output must be sufficient to make the fan status. This control strategy allows the control of variable frequency/speed drives, inlet vane or discharge dampers that control static pressure within the air handling system. The static pressure setpoint is in inches of Water Gauge (WG) or Pascals for metric units. The static pressure proportional band, integration value, and derivative weight determine the gain of the control loop. An integration value is always recommended to eliminate the proportional offset in this control loop, as precise static pressure control is required in most cases. Usually derivative control action is not necessary, and the derivative weight should be input as 0. The system adds the static pressure offset value to the PID control calculation and usually remains at 0. The static pressure deadband value establishes a range above and below the static pressure setpoint where the error is considered 0. The deadband is applied above and below the static pressure setpoint. If the static sensor becomes unreliable, the command to the static pressure control device equals 0%. In the volume matching strategy, the return fan is to track the CFM delivery of the supply fan.
AHU Applications Application Note 60
RFMSSFO
0
0
Static Integration Term
FailSoft
0
DelayOFFSupply Airflow
CFMCalculation
Supply VolumeVelocity Pressure SUB
Return Fan Offset
Process VariableSetpoint
Proportional BandIntegrationDerivative
OffsetDeadband
AOReturnFanControl
CFMCalculation
Return Volume Velocity Pressure
Duct Area
Duct Area
Unocc CFM DifferentialOcc CFM Differential
Occupancy
Figure 48: Single Supply and Return Fan, Volume Matching, without Static Ramp
The controller uses the CFM differential as the setpoint, and calculates the controlled variable or feedback, by subtracting the return CFM from the supply CFM. The return volume proportional band integration value and derivative weight determines the gain of the return fan control loop. An integration value is always recommended to eliminate the proportional offset in this control loop, as precise volume control is required in most cases. Usually, derivative control action is not necessary and the derivative weight should be input as 0. If the return fan is started by means other than the AHU, supply fan status enables the return fan control integration. If the AHU supply fan is ramped on startup (supply or return started first), an active supply fan ramp or return fan status enables the return fan control integration. If the AHU starts the return fan first and there is no ramp of the supply fan on startup, the return fan integration is enabled for two minutes after the return fan command is on to allow for fan status to make. Return fan command and return fan not in alarm enables the return fan control integration. If the supply fan or return fan CFM calculation is unreliable, the output to the return fan equals 0%.
AHU Applications Application Note 61
Single Supply, Low/High Speed Control This strategy controls a two speed fan motor. Upon startup, the low speed fan energizes. After a five minute delay the controller analyzes the velocity pressure of the supply air and allows the high speed circuit to energize. This strategy always starts the low speed fan first when a supply fan command is received.
BO13
Supply FanCommand
BOLow Speed
Five MinutesCoast Time
BOHigh SpeedDelay
OnAND Delay
On
Compare
Coast TimeTwo Minutes
ADD
DelayOff
NOT DelayOn
Supply VelocityPressure
SetpointDifferential
Figure 49: Single Supply Fan; Low/High Speed Control If the velocity pressure is above the high speed velocity pressure setpoint, the controller commands the fan off, for the time period entered for coast time. After this timer expires, the high speed fan circuit energizes. When the velocity pressure decreases below the high speed velocity pressure setpoint minus the velocity pressure differential, the fan de-energizes again for a period equal to the coast time. When this timer expires, the low speed circuit fan energizes.
Constant Volume The fans start in the Occupied mode, Warmup mode, Vent or Purge mode, intermittent night operation, or setup/setback operation.
AHU Applications Application Note 62
Using an AHU Application in a UNT Controller With HVAC PRO Release 5.10 or later, it is possible to select a UNT as a target device for an AHU application. Valid target devices include all UNT1nn-n controllers. With the 8 K UNTs, the question is not whether the configuration will fit in the controller, but if there are enough hardware points on the UNT for the configuration. Most likely, you will run out of Analog Output (AO) points first. If this is the case, you can use a Zone Bus actuator like the M100 motor actuator for the extra AOs.
Table 1: Default Zone Bus Addresses for Analog Outputs Output Address Damper Command 20 Preheat Valve 21 Heating Valve 22 Cooling Valve 23 Humid Valve 24 Supply Fan Cntl 25 Return Fan Cntl 26
The Zone Bus addresses listed in Table 1 are based on the default locations of analog outputs assigned by HVAC PRO during the Question and Answer session. If you move the analog output location within an HVAC PRO configuration, HVAC PRO will recalculate the Zone Bus address using the equation: ZB Address = AO Number + 19.
Default Point Types The AHU application Question and Answer session assigns point type defaults that are compatible with AHU controller hardware, but may not be compatible with UNT controller hardware. AHU controllers support the Current type for analog input sensors and analog output points. Since the Current type is not supported by the UNT controller hardware, any analog input sensor or analog output point configured as Current must be changed before targeting the application to a UNT controller. Voltage type is supported.
AHU Applications Application Note 63
Instant Off Feature When using staged outputs in the UNT, the Binary Output (BO) Instant Off feature operates properly. So if the stages are on, and shutdown is turned on or airflow status is open, the staged outputs will ignore the minimum on timers and go off immediately. The Instant Off feature is also available on AHU controllers with firmware Revision C06 or later.
Momentary Start/Stop Momentary start/stop points will operate properly on the UNT controller when loaded with an AHU configuration.
Accumulator Point The accumulator point (BI-4) on the UNT controller operates as usual, even when the UNT controller is loaded with an AHU configuration.
Binary Parameters The locations of certain binary parameters loaded by the AHU application Question and Answer session are not supported by UNT1nn-0 devices. All UNT1nn-0 devices are removed from the Target Device Selection if you select anything but Hardware BI Point or Hardware AI Point to initiate any modes, as shown in Table 2.
Table 2: Mode/Command Mode/Command Name BD Address Cooling Lockout Cmd 205 Econ Switch 199 Heating Lockout Cmd 204 Occupied Command 196 Preht Lockout Cmd 203 Purge Command 194 Shutdown Command 197 Summer/Winter 198 Vent Command 193 Warmup/Cooldown Command 195
The following message will appear in the Reason Not Allowed window: Device UNT1nn-0 does not support BYTE (mode/command name) at address nnn. The location where these parameters would exist in the AHU controller is not supported in the UNT1nn-0.
AHU Applications Application Note 64
Procedure Overview Table 3: Using AHU Applications To Do This Follow These Steps: Create a Mixed Air Single Path Application
From the File menu, select New. Select Air Handlers MA Single Path. Answer the questions as they are presented. When finished, go to the Economizer section.
Create a 100% Outside Air Single Path Application
From the File menu, select New. Select Air Handlers 100% OA Single Path. Answer the questions as they are presented. When finished, go to the Heat Recovery for 100% Outside Air section.
Create a Mixed Air Dual Path or 100% Outside Air Dual Path Application
From the File menu, select New. Select Air Handlers MA Dual Path or Air Handlers 100% OA Dual Path. Answer the questions as they are presented. After completing the Mixed Air Dual Path section of the question/answer path, go to the Economizer section. After completing the 100% Outside Air Dual Path section of the question/answer path, go to the Heat Recovery for 100% Outside Air section, since there is no Economizer available for 100% OA units.
Complete the Heat Recovery for 100% Outside Air Question/Answer Path
Answer the questions as they are presented. When finished, go to the Preheat section.
Complete the Economizer Question/Answer Path
Answer the questions as they are presented. When finished, go to the Minimum Duct Requirements section.
Complete the Minimum Duct Requirements Question/Answer Path
Answer the questions as they are presented. When finished, go to the Vent and Purge section.
Complete the Vent and Purge Question/Answer Path
Answer the questions as they are presented. When finished, go to the Preheat section.
Complete the Preheat Question/Answer Path
Answer the questions as they are presented. When finished, go to the Heating section.
Complete the Heating Question/Answer Path
Answer the questions as they are presented. After completing the Heating section of the question/answer path for none, modulated single coil, staged, or 2-position valve with face and bypass, go to the Cooling section. After completing the Heating section of the question/answer path for modulated common heating and cooling coil, go to the Dehumidification section.
Complete the Cooling Question/Answer Path
Answer the questions as they are presented. After completing the Cooling section of the question/answer path for None, go to the Humidification section. For all other cooling strategies, go to the Dehumidification section.
Complete the Dehumidification Question/Answer Path
Answer the questions as they are presented. When finished, go to the Humidification section.
Complete the Humidification Question/Answer Path
Answer the questions as they are presented. When finished, go to the Modes of Operation section.
Complete the Modes of Operation Question/Answer Path
Answer the questions as they are presented.
Complete the Fan System Control Question/Answer Path
Answer the questions as they are presented.
AHU Applications Application Note 65
Detailed Procedures Creating a Mixed Air Single Path Application
To create a mixed air single path application: 1. From the File menu, select New. 2. Select Air Handlers MA Single Path. 3. Answer the questions as they are presented (Figure 50), using the
control strategy information in the Key Concepts section and the information presented in the remainder of this procedure as a guide.
4. After the Mixed Air Single Path section, the question/answer path continues on to the Economizer section.
Select the Control Strategy
No Remote Setpoint
Slider
MASP
Supply Air Resetfrom Return Temperature
RoomControl
Supply Air Reset from Zone
Temperature
Room Controlof Cooling
Room Reset of Heating
ConstantDischarge AirTemperature
Return AirControl
SingleZone Setpoint
DualZone Setpoints
Is a RemoteZone Setpoint
Needed?
Are Remote ZoneSetpoints forHeating and
Cooling Needed?
ToEconomizer
Section
TMZ Digital Room Sensor
No Dual Remote Setpoint Sliders
TMZ Digital RoomSensor
No Remote Setpoint
Slider
Is a RemoteZone Setpoint
Needed?
TMZ Digital Room Sensor
Select the Setpoint Type
Figure 50: Mixed Air Single Path Questions and Answers
AHU Applications Application Note 66
Select the Control Strategy See the Key Concepts section for descriptions of each of the control strategy options.
Select the Setpoint Type Choose among the options in Table 4.
Table 4: Select the Setpoint Type Option Description Single Zone Setpoint
Single setpoint uses a zone setpoint and a deadband. When the zone temperature is within the heating deadband, the zone heating and cooling commands are 0%.
Dual Zone Setpoints
The dual setpoints strategy uses separate cooling and heating setpoints. When the zone temperature is between the cooling and heating setpoints, the zone heating and cooling commands are 0%.
Is a Remote Zone Setpoint Needed? Choose among the options in Table 5.
Table 5: Is a Remote Zone Setpoint Needed? Option Description No The zone setpoint and heating deadband used for sequencing
heating and cooling outputs for all modes of operation are defined in HVAC PRO.
Remote Setpoint Slider
An AI is defined as the remote zone setpoint. A single cooling setpoint adjustment from a room thermostat is used to establish the zone setpoints for sequencing heating and cooling during the Occupied mode. The unoccupied and standby setpoints defined in HVAC PRO are used during the Unoccupied and Standby modes. If the remote AI becomes unreliable, the controller will use the occupied zone setpoints defined in HVAC PRO.
TMZ Digital Room Sensor
Points, parameters and logic are assigned to provide setpoints adjustable from a either a supervisory system, a configuration/commissioning tool, or a TMZ Digital Room Sensor. The heating and cooling setpoints are adjustable from the supervisory system, configuration/commissioning tool or TMZ. The Heating Setpoint and Cooling Setpoint are adjustable with default values of 20°C (68.0°F) and 22°C (72°F) respectively. Additional parameters are loaded to provide information for the TMZ to display to the user.
AHU Applications Application Note 67
Are Remote Zone Setpoints for Heating and Cooling Needed? Choose among the options in Table 6.
Table 6: Are Remote Zone Setpoints for Heating and Cooling Needed? Option Description No The zone setpoints used for sequencing heating and cooling
outputs for all modes of operation are defined in HVAC PRO. Dual Remote Setpoint Sliders
Two AIs are defined as the heating and cooling setpoints. Separate heating and cooling setpoint adjustments are used to establish the zone setpoints for sequencing heating and cooling during the Occupied mode. The unoccupied and standby setpoints defined in HVAC PRO are used during Unoccupied and Standby modes. If the remote AI becomes unreliable, the controller will use the occupied zone setpoints defined in HVAC PRO.
TMZ Remote Digital Sensor
Points, parameters and logic are assigned to provide setpoints adjustable from a either a supervisory system, a configuration/commissioning tool, or a TMZ digital room sensor. The heating and cooling setpoints are adjustable from the supervisory system, configuration/commissioning tool or TMZ. The Heating Setpoint and Cooling Setpoint are adjustable with default values of 20°C (68°F) and 22°C (72°F) respectively. Additional parameters are loaded to provide information for the TMZ to display to the user.
AHU Applications Application Note 68
Creating a 100% Outside Air Single Path Application To create a 100% outside air single path application: 1. From the File menu, select New. 2. Select Air Handlers 100% OA Single Path. 3. Answer the questions as they are presented (Figure 51), using the
information presented in the Key Concepts section and the Mixed Single Air Path Applications topic as a guide.
4. After the 100% Outside Air Single Path section, the question/answer path continues on to the Heat Recovery for 100% Outside Air section.
100OASP
Select the Setpoint Type
RoomControl
RoomControl Cooling
Room ResetHeating
Supply AirReset FromZone Temp
ExhaustAir TempControl
ConstantDischarge
Air Temperature
Single ZoneSetpoint
Dual ZoneSetpoints
Is a Remote ZoneSetpoint Needed?
Are Remote ZoneSetpoints forHeating and
Cooling Needed?
Select the Control Strategy
To Heat Recovery
Section
No Remote Setpoint Slider
TMZ Digital Room Sensor
No Dual Remote Setpoint Sliders
TMZ Digital Room Sensor
Figure 51: 100% Outside Air Single Path Questions and Answers
AHU Applications Application Note 69
Creating a Mixed Air Dual Path or 100% Outside Air Dual Path Application
To create a mixed air dual path or 100% outside air dual path application: 1. From the File menu, select New. 2. Select Air Handlers MA Dual Path or Air Handlers 100% OA
Dual Path. 3. Answer the questions as they are presented (Figures 52 and 53),
using the information presented in the Key Concepts section as a guide.
4. After the Mixed Air Dual Path section, the question/answer path continues on to the Economizer section. After the 100% Outside Air Dual Path section, the question/answer path continues on to the Heat Recovery for 100% Outside Air section, since there is no Economizer available for 100% OA units.
Mixed Air Dual Path
To Economizer Section
MultizoneHot/Cold
Deck Reset
MultizoneZone Control
Dual DuctHot/Cold
Deck Reset
Dual DuctZone Control
MADP
Figure 52: Mixed Air Dual Path Questions and Answers
100% Outside Air Dual Path
To Heat Recovery Section
MultizoneHot/Cold
Deck Reset
MultizoneZone Control
Dual DuctHot/Cold
Deck Reset
Dual DuctZone Control
100OADP
Figure 53: 100% Outside Air Dual Path Questions and Answers
AHU Applications Application Note 70
Completing the Heat Recovery for 100% Outside Air Question/Answer Path
To complete the heat recovery for 100% outside air question/answer path: 1. Answer the questions as they are presented (Figure 54), using the
information presented in the Key Concepts section and the remainder of this procedure as a guide.
2. After the Heat Recovery for 100% Outside Air section, the question/answer path continues on to the Preheat section.
HEATREC
None
Select the Analog Input
No Yes
Maintained MomentaryPulse
ToPreheatSection
Select the Type of Heat Recovery Device:
2 Pos Output fromAnalog Input Sensor
OutdoorAir Sensor
DischargeAir Sensor
Run AroundGlycol Loop
Type of PumpOutput
Is pump start neededupon sensor entering
prop band?
Figure 54: Heat Recovery for 100% Outside Air Questions and Answers
AHU Applications Application Note 71
Select the Heat Recovery Type Choose among the options in Table 7.
Table 7: Select the Heat Recovery Type Option Description None No point/parameter assignment or logic sequence for this
selection. 2-Position Output from Analog Input Sensor
See the Key Concepts section for a description of this option.
Run Around Glycol Loop
See the Key Concepts section for a description of this option.
Is Pump Start Needed upon Sensor Entering Prop Band? Choose among the options in Table 8.
Table 8: Is Pump Start Needed upon Sensor Entering Prop Band? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes The pump start option allows a pump operation whenever the
command to the heat recovery device is greater than 1% open.
Type of Pump Output Choose among the options in Table 9.
Table 9: Type of Pump Output Option Description Maintained A single binary output is assigned. It will be energized when the
pump command is on and de-energized when the pump command is off.
Momentary Pulse
A pair of binary outputs are assigned. The start output will be energized momentarily when the pump command is on and the stop output will be energized momentarily when the pump command is off. A momentary output has a pulse duration of 1.5 seconds.
AHU Applications Application Note 72
Completing the Economizer Question/Answer Path To complete the economizer question/answer path: 1. Answer the questions as they are presented (Figure 55), using the
information presented in the Key Concepts section and the remainder of this procedure as a guide.
2. After the Economizer section, the question/answer path continues on to the Minimum Duct Requirements section.
Select Damper Control Strategy
Which setpoint shall be used?
No
Select The Economizer Switchover Strategy
None Dry Bulb
ToMinimum DuctRequirements
Section
Yes
Separate Mixed Air Closed Loop Sequenced with Heatingand Cooling
Is a Mixed AirLow LimitRequired?
SeparateMixed Air Setpoint
DischargeAir Setpoint
(Cold Deck forDual Path)
Only Asked If Strategy isDischarge Control or
Supply Air Reset
Software(N2) Command
HardwareBI point
EnthalpyComparison
Outdoor AirEnthalpy
FixedTemperatureDifferential
ECON
NoYes
Is Low Limit Override of Minimum Required?
Figure 55: Economizer
AHU Applications Application Note 73
Select the Damper Control Strategy Choose among the options in Table 10.
Table 10: Select the Damper Control Strategy Option Description Separate Mixed Air Closed Loop
This strategy provides a separate control loop for the outdoor air dampers based on the mixed air sensor. A temperature setpoint is selected and maintained when free cooling is available and economizer is on. The direct acting output shall open the outside air dampers from minimum position to 100% as the mixed air temperature rises through the proportional band. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control.
Sequenced with Heating and Cooling
This strategy allows the sequencing of the outside air dampers with the mechanical cooling device when free cooling is available and economizer is on. The direct acting output shall open the outside air dampers from minimum position to 100% as the controlled temperature rises through the economizer proportional band. The economizer proportional band must not exceed the sum of the cooling deadband and the cooling proportional band. If this is not done, the economizer output will stop increasing when the cooling output reaches 100%. When the Economizer mode is off (free cooling not available), an alternate cooling deadband is used to shift the cooling proportional band left towards the control setpoint. This causes mechanical cooling to modulate or energize at a temperature closer to the control setpoint in comparison to the normal cooling deadband when free cooling is available. The cooling integration term for the mechanical cooling device is also used by the economizer dampers.
Which Setpoint Shall Be Used? Choose among the options in Table 11.
Table 11: Which Setpoint Shall Be Used? Option Description Separate Mixed Air Setpoint
A mixed air setpoint shall be added to the parameters list for mixed air temperature control.
Discharge Air Setpoint (Cold Deck for Dual Path)
The mixed air closed loop will maintain the same setpoint as the discharge or supply air loop (cold deck for dual path). The actual mixed air setpoint will be available for the user to monitor.
AHU Applications Application Note 74
Is a Mixed Air Low Limit Required? Choose among the options in Table 12.
Table 12: Is a Mixed Air Low Limit Required? Option Description Yes A mixed air temperature sensor will be assigned to an AI and will
be used to maintain the low limit logic for the economizer cycle. Control will be achieved through a reverse acting PI algorithm that will back off the economizer command and position the damper to maintain the low limit setpoint. The mixed air low limit control will override the minimum position setting if the mixed temperature continues to drop below setpoint which can occur with low ambient conditions in the outdoor air. If you desire a minimum position regardless of the mixed air low limit logic (for example, you are not in danger of freezing mechanical equipment), use a damper offset which will not allow the damper to go below this value during Occupied mode. Integration has been added to this control loop to eliminate the inherent offset associated with proportional only control.
No No point/parameter assignment or logic sequence for this selection.
Is Low Limit Override of Minimum Required? Choose among the options in Table 13.
Table 13: Is Low Limit Override of Minimum Required? Option Description Yes A mixed air temperature sensor will be assigned to an AI and will
be used to maintain the low limit logic for the economizer cycle. Control will be achieved through a reverse acting PI algorithm that will back off the economizer command and position the damper to maintain the low limit setpoint. The mixed air low limit control will override the minimum position setting if the mixed temperature continues to drop below setpoint which can occur with low ambient conditions in the outdoor air. Integration has been added to this control loop to eliminate the inherent offset associated with proportional only control.
No No point/parameter assignment or logic sequence for this selection.
Select Economizer Switchover Strategy See the Key Concepts section for a description of the economizer switchover strategy options.
AHU Applications Application Note 75
Completing the Minimum Duct Requirements Question/Answer Path
To complete the minimum duct requirements question/answer path: 1. Answer the questions as they are presented (Figure 56), using the
information presented in the remainder of this procedure as a guide.
2. After the Minimum Duct Requirements section, the question/answer path continues on to the Vent and Purge section.
Is a Separate Minimum Duct used for minimum position?
No
2 Position
Pitot Tube0%
Yes
How Is the Minimum DamperControlled
Minimum Closed LoopVolume Control
Select Type of Air Flow Measuring
Station
Scaled Input-Flow StationThermistor
Is Minimum Damper PositionReset from an Air Quality
Sensor Needed?
MinimumPosition
Last ReliableCommand
For Unreliable Outdoor Airor Control Sensor
Command Outdoor Air Damper to:
For Unreliable Outdoor Airor Control Sensor
Command Outdoor Air Damper to:
Is Minimum Damper PositionReset from an Air Quality Sensor
Needed?
ToVent and Purge
Section
No Yes
No Yes
0%MinimumPosition
Last ReliableCommand
MINDUCT
Figure 56: Minimum Duct Requirements
AHU Applications Application Note 76
Is a Separate Minimum Duct Used for Minimum Position? Choose among the options in Table 14.
Table 14: Is a Separate Minimum Duct Used for Minimum Position? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes A minimum damper control strategy must be selected by the user,
either 2-position or minimum closed loop volume control. See How is the Minimum Damper Controlled? for logic and point assignments.
Is Minimum Damper Position Reset from an Air Quality Sensor Needed? Choose among the options in Table 15.
Table 15: Is Minimum Damper Position Reset from an Air Quality Sensor Needed? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes An input from an air quality sensor resets the minimum position of
the outdoor air damper to an increased value (Figure 57). The controller does this through the inputs of indoor air quality low limit and indoor air quality reset band. These inputs adjust the minimum position setpoint from minimum position through the minimum position reset band. The indoor air quality defaults are in reference to a carbon dioxide sensor that indicates Parts Per Million (PPM). The minimum position reset schedule is in percent position or CFM, depending upon the type of minimum damper strategy selected. High carbon dioxide is usually a good indication that more outside air is required. However, low carbon dioxide is not always a good indication of contaminant free air.
IAQ2
Occupied
Air Quality SensorAir Quality Low Limit
Air Quality Reset BandMinimum Position
Minimum Reset Band
Reset
IAQ Minimum Setpoint
Minimum Position
(% or CFM)
0
12
34 1 2
3
4
Figure 57: Minimum Damper Reset from Air Quality Sensor
AHU Applications Application Note 77
For Unreliable Outdoor Air or Control Sensor, Command Outdoor Air Damper To Choose among the options in Table 16.
Table 16: For Unreliable Outdoor Air or Control Sensor, Command Outdoor Air Damper To Option Description Minimum Position
Drive the damper to the minimum position.
0% Drive the damper to the 0% open position. Last Reliable Command
Hold the output at the last reliable position.
How is the Minimum Damper Controlled? Choose among the options in Table 17.
Table 17: How is the Minimum Damper Controlled? Option Description 2-Position The 2-position strategy energizes a binary output whenever the
controller switches into the Occupied mode of operation (Figure 58). During the Unoccupied or Shutdown mode, the binary output for 2-position control is off. During the Vent or Purge mode, the controller energizes the binary output (damper) even if the controller is in the Unoccupied mode.
Minimum Closed Loop Volume Control
The minimum volume closed loop strategy allows control to a minimum air volume setpoint (CFM) via conventional PI control (Figure 59). As the volume (CFM) of air through an airflow measuring station decreases below the minimum volume setpoint and into the CFM proportional band, the minimum damper is modulated open. The CFM deadband suspends any change in the control output when the actual CFM is within the this deadband region. The full input deadband value is in effect on the positive and negative side of the CFM setpoint. Integration may be added to this control loop to eliminate the inherent offset associated with proportional only control. The minimum duct area input is the square foot area of the airflow measuring station (provided by device manufacturer). The area is required by the controller to calculate the CFM. The CFM offset, is a value in percent that the controller adds to the command after it performs the proportional and integration control calculation.
Occupied
AirflowPurge Vent
BO
Shutdown
0 SMD2PDNOTWarmup
OR OR OR AND
Figure 58: 2-Position Minimum Damper
AHU Applications Application Note 78
MPMCLD2CFM = (Velocity) x (ft )2
CFM Integration
AI Linearized Velocity Input
AIMinimum Damper
Airflow
Supply Air Commandv
ORNOT
CFMCalculation
(Linear)
PI Control
NOT OR
From Air Quality Reset Logic
(If Used)
00 or100
FailSoft 0
CFMCalculation
P
Airflow Shutdown
0Duct Area (ft )2
Constant (K)Duct Area (ft )2
CFM = 4005( P /K ) (ft ) 2
AI Velocity Pressure
Minimum Volume CFM Setpoint
CFM Proportional BandCFM Integration
CFM OffsetCFM Deadband
1
2
12
Figure 59: Minimum Volume Closed Loop Application
Select the Type of Air Flow Measuring Station Choose among the options in Table 18.
Table 18: Select the Type of Air Flow Measuring Station Option Description Pitot Tube This selection is required when the controller needs to calculate
the square root of the velocity pressure reading. The area of the face of the airflow station is required, and a constant is required to extract any amplification of the velocity pressure that is present in the design of the Pitot tube traverse. The formula for the CFM calculation of the Pitot tube method is:
KPv4005ACFM ∗∗=
Where: Pv = velocity pressure (in. WG) K = constant (provided by the manufacturer) A = area of the airflow station (sq ft)
Scaled Input-Flow Station (Thermistor)
This selection is intended for a packaged airflow station having a linear output ranged in velocity (FPM) or volume (CFM). In cases where the airflow station outputs a linear CFM signal, adjust the value for the area of the airflow measuring station to 1.0. CFM = (V)(A) Where: V = velocity (ft/min) A = area of the airflow station (sq ft)
AHU Applications Application Note 79
Completing the Vent and Purge Question/Answer Path To complete the vent and purge question/answer path: 1. Answer the questions as they are presented (Figure 60), using the
information presented in the remainder of this procedure as a guide.
2. After the Vent and Purge section, the question/answer path continues on to the Preheat section.
Is Vent and Purge Mode Needed?
No
Select the Method to Control the Vent Mode:
Select the Method to Control the Purge Mode:
To Preheat Section
Yes
Software(N2) Command
HardwareBI point
Both withBI backup
Both canactivate
VENTPURG
Software(N2) Command
HardwareBI point
Both withBI backup
Both canactivate
Figure 60: Vent and Purge
AHU Applications Application Note 80
Is Vent and Purge Mode Needed? Choose among the options in Table 19.
Table 19: Is Vent and Purge Mode Needed? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes The Vent and Purge modes open the outdoor air damper to 100%
when the controller commands it to on. The difference between the two modes is purge shuts off all mechanical heating, cooling, and humidification while vent allows all heating, cooling, and humidification to remain in control. If the controller commands Vent and Purge modes on simultaneously, Vent mode takes priority. Both modes are active during Occupied or Unoccupied modes of operation but are not effective during the Shutdown mode. The outdoor air dampers will not open until the supply airflow status is on. Either mode energizes the supply fan start command.
Select the Method to Control the Vent Mode Choose among the options in Table 20.
Table 20: Select the Method to Control the Vent Mode Option Description Software (N2) Command
A Vent mode binary data point is provided for a Facility Management System (FMS) to command. If communications are lost with the FMS, the controller will maintain the last commanded state for ten minutes. The default of the Vent mode is off.
Hardware BI Point
A hardware binary input is provided to switch the controller into the Vent mode; when the contact is closed, the Vent mode will be active.
Both with BI Backup
A Vent mode binary data point is provided for a facility management system to command. If communication with the FMS is lost, the status of the binary input is used to determine Vent mode.
Both can Activate
A Vent mode binary data point is provided for a facility management system to command. A hardware binary input is also provided to switch the controller into Vent mode. Either point can place the controller into the Vent mode. Both points must be off for the controller to release to the previous mode.
AHU Applications Application Note 81
Select the Method to Control the Purge Mode Choose among the options in Table 21.
Table 21: Select the Method to Control the Purge Mode Option Description Software (N2) Command
A Purge mode binary data point is provided for a facility management system to command. If communication is lost with the FMS, the controller will maintain the last commanded state for ten minutes. The default of the Purge mode is off.
Hardware BI Point
A hardware binary input is provided to switch the controller into the Purge mode; when the contact is closed, the Purge mode will be active.
Both with BI Backup
A Purge mode binary data point is provided for a facility management system to command. If communication with the FMS is lost, the status of the binary input is used to determine Purge mode.
Both can Activate
A Purge mode binary data point is provided for a facility management system to command. A hardware binary input is also provided to switch the controller into Purge mode. Either point can place the controller into the Purge mode. Both points must be off for the controller to release to the previous mode.
Completing the Preheat Question/Answer Path To complete the preheat question/answer path: 1. Answer the questions as they are presented (Figure 61), using the
information presented in the remainder of this procedure as a guide.
2. After the Preheat section, the question/answer path continues on to the Heating section.
AHU Applications Application Note 82
PREHEAT
Select Type of Preheat Control Strategy
No Yes
None
0% 100%
Software (N2) Command
HardwareAI point
Both withAI backup
0% 100%
0% 100%
Is pump start upon a preheat command needed?
No Yes
Type of Output Signal
Maintained
0% 100%
No Yes
0% 100% Last Reliable Command
To Heating Section
Software (N2) Command
HardwareAI point
Both withAI backup
Should the Preheat output gogo to 0% during Shutdown?*
Yes Use loss of airflow defaults
Should the Preheat output go to 0% during Shutdown?
Yes Use loss of airflow defaults
Is Preheat Lockout from outdoor air temperature needed ?
Should the Preheat outputgo to 0% during Shutdown?*
Yes Use loss of airflow defaults
Upon loss of air flow, the valve will be commanded to:
2 Pos Steam/WaterValve (Sensor Cntl'd)
Enter the ControlSensor
OutdoorAir
MixedAir
DischargeAir
Upon loss of air flow, the valve will be commanded to:
Remain inControl
Is Preheat Lockout from outdoor air temperature needed?
Select the MethodTo Initiate Preheat Lockout
If the control sensor becomes unreliable,
command preheat valve to:
Face/Bypass w/vlvSwitch over Seq w/Htg Clg*
Upon loss of airflow,the value will be commanded to:
Remain inControl
Select the Methodto Initiate Preheat Lockout
If the control sensor becomes unreliable,
command preheat valve to:
ModulatedSingle Coil
Select thePreheat Control
Strategy
Closed Loopwith separate
sensor
Sequenced with Heating and Cooling*
Remain inControl
MomentaryPulse
G
H
* Not an option on dual path units
Figure 61: Preheat
AHU Applications Application Note 83
Figure 62: Preheat (Cont.)
AHU Applications Application Note 84
Select the Type of Preheat Device Choose among the options in Table 22.
Table 22: Select the Type of Preheat Device Option Description None No point/parameter assignment or logic sequence for this
selection. 2-Position Steam/Water Valve (Sensor Cntl’d)
See the Key Concepts section for a description of this option.
Face and Bypass w/Vlv Switch over Seq w/Htg Clg
See the Key Concepts section for a description of this option.
Modulated Single Coil
See the Key Concepts section for a description of this option.
Staged See the Key Concepts section for a description of this option.
Enter the Control Sensor (2-Position Only) Choose among the options in Table 23.
Table 23: Enter the Control Sensor (2-Position Only) Option Description Outdoor Air When the outdoor air temperature falls below the preheat low limit
setpoint, the controller commands a binary output to on. When the outdoor air temperature rises above the preheat low limit setpoint plus the differential, the BO will be commanded off.
Mixed Air When the mixed air temperature falls below the preheat low limit setpoint, the controller commands a binary output to on. When the mixed air temperature rises above the preheat low limit setpoint plus the differential, the BO will be commanded off.
Discharge Air
When the discharge air temperature falls below the preheat low limit setpoint, the controller commands a binary output to on. When the discharge air temperature rises above the preheat low limit setpoint plus the differential, the BO will be commanded off.
AHU Applications Application Note 85
Should the Preheat Command Go to 0% on Shutdown? Choose among the options in Table 24.
Table 24: Should the Preheat Command Go to 0% on Shutdown? Option Description Yes When the Shutdown mode is on, the controlled device will be
commanded to 0%. Use Loss of Airflow Defaults
The Shutdown mode will have no effect on the controlled device. Shutdown will turn the fan off causing the loss of airflow. The position of the controlled device will be determined by how the Loss of Air Flow question is answered.
Upon Loss of Air Flow, the Valve will be Commanded To Choose among the options in Table 25.
Table 25: Upon Loss of Air Flow, the Valve will be Commanded To Option Description 0% Drive the preheat valve to the 0% open position and bypass
damper to 0%. 100% Drive the preheat valve to the 100% open position and bypass
damper to 0%. Remain In Control
Continue to control as normal. This strategy is intended to be used only where the coil has an effect on the sensor when airflow is off, that is the sensor is in close proximity to the coil.
Is Preheat Lockout from Outdoor Air Temperature Needed? Choose among the options in Table 26.
Table 26: Is Preheat Lockout from Outdoor Air Temperature Needed? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes All preheat control strategies may be locked out. The preheat
lockout can be initiated from a controller input, or over the N2 Bus by a FMS.
AHU Applications Application Note 86
Select the Method to Initiate Preheat Lockout
HeatingLockout
N2 Command
Outdoor Air TemperatureHeating Lockout Setpoint
Differential
Compare
HeatingLockout
Outdoor Air TemperatureHeating Lockout Setpoint
Differential
Compare
N2 Command withAI Backup
AI Switch
N2 Com Status
N2 Command
HeatingLockout
CommandLOCKOUT
Figure 63: Lockout Choose among the options in Table 27.
Table 27: Select the Method to Initiate Preheat Lockout Option Description Software (N2) Command
A binary data point is provided to initiate the preheat lockout. If communication is lost with the FMS, the controller will maintain the last commanded state for ten minutes. The default of the preheat lockout is off.
Hardware AI Point
An analog input is assigned for an outside air temperature sensor. When the outside air temperature is above the preheat lockout setpoint, the preheat will be locked out; when the outside air temperature is below the setpoint minus the differential, the preheat will be enabled. If the analog input becomes unreliable, the preheat will failsoft enabled.
Both with AI Backup
A binary data point is provided to initiate the preheat lockout. If communication is lost with the FMS, the controller will use the outside air sensor as a backup for the preheat lockout decision. In the event N2 communications is lost, when the outside air temperature is above the preheat lockout setpoint, the preheat will be locked out; when the outside air temperature is below the setpoint minus the differential, the preheat will be enabled. If the analog input becomes unreliable, the preheat will failsoft enabled.
AHU Applications Application Note 87
If the Control Sensor Becomes Unreliable, Command Preheat Valve To Choose among the options in Table 28.
Table 28: If the Control Sensor Becomes Unreliable, Command Preheat Valve To Option Description 0% Drive the valve to the 0% open position. 100% Drive the valve to the 100% open position. Last Reliable Command
Hold the output at the last reliable position. This option is not available on a 2-position steam strategy.
Is Pump Start upon a Preheat Command Needed? Choose among the options in Table 29.
Table 29: Is Pump Start upon a Preheat Command Needed? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes Preheat Control Strategies “Face and Bypass Valve Sequenced
with Heating and Cooling” and “Modulated Single Coil” have the option of an additional output assigned for a pump. This output will be energized when the heating command is greater than 1%.
Type of Output Signal Choose among the options in Table 30.
Table 30: Type of Output Signal Option Description Maintained A single binary output is assigned. It will be energized when the
pump command is on and de-energized when the pump command is off.
Momentary Pulse
A pair of binary outputs are assigned. The start output will be energized momentarily when the pump command is on and the stop output will be energized momentarily when the pump command is off. A momentary output has a pulse duration of 1.5 seconds.
AHU Applications Application Note 88
Select the Preheat Control Strategy (Staged and Modulated) Choose among the options in Table 31.
Table 31: Select the Preheat Control Strategy (Staged and Modulated) Option Description Closed Loop with Separate Sensor
When configured as a closed loop, the preheat setpoint with separate sensor, the preheat setpoint, proportional band, integration value, offset, and deadband control the action of the preheat device.
Part of Main Ctl Sequenced with Heating and Cooling
When configured as sequenced with heating and cooling, the preheat proportional band allows the preheat device to be controlled as the control temperature decreases below the control setpoint. The integration term is shared with the heating device. This option is not available on Dual Path units.
Sequencer - Number of Stages See the Key Concepts section for a description of these options.
Is Vernier Control Needed? (AO Control for % after Stage) Choose among the options in Table 32.
Table 32: Is Vernier Control Needed? (AO Control for % after Stage) Option Description No No point/parameter assignment or logic sequence for this
selection. Yes This strategy allows an analog output to be commanded from 0 to
100% between each stage of preheat. The analog command increases from 0 to 100% as the sequencer command from the control strategy increases from 0 to the starting point of the first stage. When you select Vernier control, the starting point of the first stage defaults to the normal proportional division of the number of stages plus one (i.e., 3 stages would start at 25, 50, and 75% commands). When the sequencer preheat command rises above the first stage on percent, the analog command begins again at 0 and increases to 100% until the sequencer command equals the starting point of the second stage. The analog output operation between each stage is consistent between all stages. The Vernier control strategy cannot be used with rotational sequencing.
AHU Applications Application Note 89
Is Rotational Sequencing Needed? Choose among the options in Table 33.
Table 33: Is Rotational Sequencing Needed? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes The rotational sequencing option allows each stage to be the next
started (in order) after the controller turns off the first stage. For example, if Stages 1 - 2 - 3 - 4 energize and then turn off in the opposite order, the next sequence is 2 - 3 - 4 - 1. This new order de-energizes in reverse, and then reorders as 3 - 4 - 1 - 2. When you select the rotational sequencing feature, you cannot use Vernier control.
Completing the Heating Question/Answer Path To complete the heating question/answer path: 1. Answer the questions as they are presented (Figure 64), using the
information presented in the Key Concepts section and the remainder of this procedure as a guide.
2. After the Heating section, the question/answer path continues on either to the Cooling section (for Heating device=None, Modulated single coil, Staged, or 2-Position valve with face and bypass) or the Dehumidification section (for Heating device= Modulated common heating and cooling coil).
AHU Applications Application Note 90
Select the type of heating device:
None Modulatedsingle coil
Modulated common htg and clg coil
Staged 2 Position valve w/face and bypass
B C
No Yes
Will pump startupon heating commandgreater than 0% open?
Type of output signal:
Maintained Momentarypulse
No Yes
Is outdoor air lockoutof heating needed?
Select the method to initiate
Heating Lockout:
If the control sensor becomes unreliable, command heating valve to:
0% 100% Last Reliable command
Upon loss of air flow, the heating valve will be commanded to:
0% 100% Remain in Control
A
Method of determining heating or cooling:
Software(N2)
command
Hardware BI point
HardwareAI point
Will pump start upon a htg/clg command greater
than 0% open?
No Yes
Type of output signal:
Maintained Momentarypulse
No Yes
Is outdoor air lockoutof heating needed?
Select the method to initiate
Heating Lockout:
D
Software(N2)
command
Hardware BI point
HardwareAI point
Software(N2)
command
Hardware BI point
HardwareAI point
Yes Use loss of airflow defaults
Should the heating output go to 0% during shutdown
AHUHTG1
Position AdjustIncremental
Figure 64: Heating
AHU Applications Application Note 91
B
No Yes
Is outdoor air lockoutof heating needed?
Select the method to initiate
Heating Lockout:
Sequencer: No. of Stages
One Two thru Nine
Is Vernier control needed (AO control
for % control between stages)?
No Yes
Is Vernier control needed (AO control
for % control after stage)?
No Yes
Is rotational sequencing
needed?
No Yes
If the control sensor becomes unreliable,
command heating valve to:
0% 100% Last Reliable command
Does the electric heat require a 2 position command to face and bypass damper?
No Yes
A
Type of output signal:
Maintained Momentarypulse
C
No Yes
Is outdoor air lockoutof heating needed?
Select the method to initiate
Heating Lockout:
If the control sensor becomes unreliable,
command heating valve to:
0% 100% Last Reliable command
Upon loss of air flow, the heating valve will be commanded to:
0% 100% Remain in Control
To Cooling Section AHUHTG2
Yes Use loss of airflow defaults
Should the heating output go to 0% during shutdown?
Software(N2)
command
Hardware BI point
HardwareAI point
Software(N2)
command
Hardware BI point
HardwareAI point
Figure 65: Heating (Cont.)
AHU Applications Application Note 92
If the control sensor becomes unreliable,
command htg/clg valve to:
0% 100% Last Reliable command
Upon loss of air flow, the htg/clg valve will be commanded to:
0% 100% Remain in Control
To Dehumidification
Section
D
AHUHTG3
No Yes
Is outdoor air lockoutof cooling needed?
Select the method to initiate
Cooling Lockout:
Software(N2)
command
Hardware BI point
HardwareAI point
Yes Use loss of airflow defaults
Should the htg/clg output go to 0% during shutdown?
Figure 66: Heating (Cont.)
AHU Applications Application Note 93
Select the Type of Heating Device Choose among the options in Table 34.
Table 34: Select the Type of Heating Device Option Description None No point/parameter assignment or logic sequence for this
selection. Modulated Single Coil
See the Key Concepts section for a description of this option.
Modulated Common Htg and Clg Coil
See the Key Concepts section for a description of this option.
Staged See the Key Concepts section for a description of this option. 2-Position Valve w/Face and Bypass
See the Key Concepts section for a description of this option.
Position Adjust – Incremental
See the Key Concepts section for a description of this option.
Will Pump Start Upon a Heating Command Greater than 0% Open? Choose among the options in Table 35.
Table 35: Will Pump Start Upon a Heating Command Greater than 0% Open? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes The heating control strategies titled “Modulated Single Coil,”
“Common Heating and Cooling,” and “2-Position Face and Bypass Valve” have the option of an additional output assigned for a pump. This output will be energized when the heating command is greater than 1%.
AHU Applications Application Note 94
Type of Output Signal Choose among the options in Table 36.
Table 36: Type of Output Signal Option Description Maintained A single binary output is assigned. It will be energized when the
pump command is on and de-energized when the pump command is off.
Momentary Pulse
A pair of binary outputs are assigned. The start output will be energized momentarily when the pump command is on and the stop output will be energized momentarily when the pump command is off. A momentary output has a pulse duration of 1.5 seconds.
Is Outdoor Air Lockout of Heating Needed? Choose among the options in Table 37.
Table 37: Is Outdoor Air Lockout of Heating Needed? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes All heating control strategies may be locked out. The heating
lockout can be initiated from a controller input or over the N2 Bus by an FMS.
HeatingLockout
N2 Command
Outdoor Air TemperatureHeating Lockout Setpoint
Differential
Compare
HeatingLockout
Outdoor Air TemperatureHeating Lockout Setpoint
Differential
Compare
N2 Command withAI Backup
AI Switch
N2 Com Status
N2 Command
HeatingLockout
CommandLOCKOUT
Figure 67: Heating Lockout
AHU Applications Application Note 95
Select the Method to Initiate Heating Lockout Choose among the options in Table 38.
Table 38: Select the Method to Initiate Heating Lockout Option Description Software (N2) Command
A binary data point is provided to initiate the heating lockout (Figure 67). If communication is lost with the FMS, the controller will maintain the last commanded state for ten minutes. The default of the heating lockout is off.
Hardware BI Point
A hardware binary input is provided to initiate heating lockout. When the contact is closed, heating lockout is initiated.
Hardware AI Point
An analog input is assigned to outdoor air temperature, for when the outside air temperature drops below the heating lockout setpoint and differential. If the analog input becomes unreliable, the heating will failsoft enabled.
If the Control Sensor Becomes Unreliable, Command Heating Valve To Choose among the options in Table 39.
Table 39: If the Control Sensor Becomes Unreliable, Command Heating Valve To Option Description 0% Drive the valve to the 0% open position. 100% Drive the valve to the 100% open position. Last Reliable Command
Hold the output at the last reliable position.
Should the Heat Command go to 0% on Shutdown? Choose among the options in Table 40.
Table 40: Should the Heat Command go to 0% on Shutdown? Option Description Yes When the Shutdown mode is on, the controlled device will be
commanded to 0%. Use Loss of Airflow Defaults
The Shutdown mode will have no effect on the controlled device. Shutdown will turn the fan off causing the loss of airflow. The position of the controlled device will be determined by how the Loss of Air Flow question is answered.
AHU Applications Application Note 96
Upon Loss of Air Flow, the Heating Valve will be Commanded To Choose among the options in Table 41.
Table 41: Upon Loss of Air Flow, the Heating Valve will be Commanded To Option Description 0% Drive the valve to the 0% open position. 100% Drive the valve to the 100% open position. Remain In Control
Continue to control as normal. This strategy is intended to be used only where the coil has an effect on the sensor when airflow is off, that is the sensor is in close proximity to the coil.
Method of Determining Heating or Cooling Choose among the options in Table 42.
Table 42: Method of Determining Heating or Cooling Option Description Software (N2) Command
A binary data point is provided to initiate the heating/cooling switchover. If communication is lost with the FMS, the controller will maintain the last commanded state for ten minutes. The default of the sum/win is off, which will leave the AHU in Summer mode for cooling. The controller is in the Winter mode of operation when sum/win = on (1) and in the Summer mode when it is off (0).
Hardware BI Point
A binary input is provided to initiate the heating/cooling switchover. The controller is in the Winter mode of operation when sum/win = on (BI contact is closed) and in the Summer mode when it is off (BI contact is open).
Hardware AI Point
An analog input is assigned as a hot/cold water temperature sensor. The controller is in the Winter mode of operation when sum/win = on and in the Summer mode when it is off. When the AI is greater than the setpoint, sum/win = on and when the AI is less than the setpoint minus the differential, sum/win = off. The default setpoint differential is 7°C (40°F), and should remain a relatively large value if adjusted.
Sequencer - Number of Stages See the Key Concepts section for a description of these options.
AHU Applications Application Note 97
Is Vernier Control Needed (AO Control for % Control Between Stages) Choose among the options in Table 43.
Table 43: Is Vernier Control Needed (AO Control for % Control Between Stages) Option Description No No point/parameter assignment or logic sequence for this
selection. Yes This strategy allows an analog output to be commanded from 0 to
100% between each stage of heating. The analog command increases from 0 to 100% as the sequencer command from the control strategy increases from 0 to the starting point of the first stage. When you select Vernier control, the starting point of the first stage defaults to the normal proportional division of the number of stages plus one (i.e., 3 stages would start at 25, 50, and 75% commands). When the sequencer heating command rises above the first stage on percent, the analog command begins again at 0 and increases to 100% until the sequencer command equals the starting point of the second stage. The analog output operation between each stage is consistent between all stages. The Vernier control strategy cannot be used with rotational sequencing.
Is Rotational Sequencing Needed? Choose among the options in Table 44.
Table 44: Is Rotational Sequencing Needed? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes The rotational sequencing option allows each stage to be the next
started (in order) after the controller turns off the first stage. For example, if Stages 1 - 2 - 3 - 4 energize and then turn off in the opposite order, the next sequence is 2 - 3 - 4 - 1. This new order de-energizes in reverse, and then reorders as 3 - 4 - 1 - 2. When you select the rotational sequencing feature, you cannot use Vernier control.
AHU Applications Application Note 98
Does the Electric Heat Require a 2-Position Command to Face and Bypass Damper? Choose among the options in Table 45.
Table 45: Does the Electric Heat Require a 2-Position Command to Face and Bypass Damper? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes A binary output is assigned as a heat face/bypass. This output will
turn on when the heating command reaches 11% and goes back off at 1%.
Select Output Type Choose among the options in Table 46.
Table 46: Select Output Type Option Description Maintained A single binary output is assigned. It will be energized when the
valve is commanded open and de-energized when the valve is commanded closed.
Momentary Pulse
A pair of binary outputs are assigned, the open output will be energized momentarily when the valve is commanded open and the close output will be energized momentarily when the valve is commanded closed. A momentary output has a pulse duration of 1.5 seconds.
Completing the Cooling Question/Answer Path To complete the cooling question/answer path: 1. Answer the questions as they are presented (Figure 68), using the
information presented in the Key Concepts section and the remainder of this procedure as a guide.
2. After the Cooling section, the question/answer path continues on either to the Humidification section (Cooling device = None) or to the Dehumidification section (all other cooling devices).
AHU Applications Application Note 99
Select the type of cooling device:
None Modulatedsingle coil
Staged 2 Position valve w/face and bypass
If the control sensor becomes unreliable, the cooling valve
is commanded to:
0% 100% Last Reliable command
If the control sensor becomes unreliable, the cooling stages are commanded to:
0% 100% Last Reliable command
To Dehumidification
Section
Upon loss of air flow, the cooling valve will be commanded to:
0% 100% Remain in Control
No Yes
Is pump startupon cooling command
greater than 0% needed?
Type of output signal:
Maintained Momentarypulse
No Yes
Is outdoor air lockoutof cooling needed?
Select the method to initiate
Cooling Lockout:
Software (N2) Command
HardwareAI point
Both withAI backup
No Yes
Is outdoor air lockoutof cooling needed?
Select the method to initiate
Cooling Lockout:
Sequencer: No of Stages
One Two through Nine
Is Vernier control needed (AO control
for % control between stages)?
No Yes
Is Vernier control needed (AO control
for % control after stage)?
No Yes
Is rotational sequencing
needed?
No Yes
No Yes
Is outdoor air lockoutof cooling needed?
Select the method to initiate
Cooling Lockout:
Upon loss of air flow, the cooling output will
be commanded to:
0% 100%Open
Remain in Control
If the control sensor becomes unreliable, the cooling output is
commanded to:
0% 100% Last Reliable command
To Humidification
Section AHUCLG
Type of output signal:
Maintained Momentarypulse
Should the cooling outputgo to 0% during shutdown?
Yes Use loss of airflow defaults
Should the cooling outputgo to 0% during shutdown?
Yes Use loss of airflow defaults
Software (N2) Command
HardwareAI point
Both withAI backup
Software(N2)
Command
HardwareAI point
Both withAI backup
Position Adjustincremental
Figure 68: Cooling
AHU Applications Application Note 100
Select the Type of Cooling Device Choose among the options in Table 47.
Table 47: Select the Type of Cooling Device Option Description None No point/parameter assignment or logic sequence for this
selection. Note: When you select None (no cooling apparatus), HVAC PRO
does not display questions for dehumidification. Modulated Single Coil
See the Key Concepts section for a description of this option.
Staged See the Key Concepts section for a description of this option. 2-Position Valve w/Face and Bypass
See the Key Concepts section for a description of this option.
Position Adjust – Incremental
See the Key Concepts section for a description of this option.
Should the Cooling Command Go to 0% on Shutdown? Choose among the options in Table 48.
Table 48: Should the Cooling Command Go to 0% on Shutdown? Option Description Yes When the Shutdown mode is on, the controlled device will be
commanded to 0%. Use Loss of Airflow Defaults
The Shutdown mode will have no effect on the controlled device. Shutdown will turn the fan off causing the loss of airflow. The position of the controlled device will be determined by how the Loss of Air Flow question is answered.
Upon Loss of Air Flow, the Cooling Valve will be Commanded To Choose among the options in Table 49.
Table 49: Upon Loss of Air Flow, the Cooling Valve will be Commanded To Option Description 0% Drive the valve to the 0% open position. 100% Drive the valve to the 100% open position. Remain In Control
Continue to control as normal. This strategy is intended to be used only where the coil has an effect on the sensor when airflow is off, that is the sensor is in close proximity to the coil.
AHU Applications Application Note 101
Is Pump Start Upon Cooling Command Greater Than 0% Needed? Choose among the options in Table 50.
Table 50: Is Pump Start Upon Cooling Command Greater Than 0% Needed? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes The cooling control strategies titled “Modulated Single Coil,”
“Common Heating and Cooling,” and “2-Position Face and Bypass Valve” have the option of an additional output assigned for a pump. This output will be energized when the cooling command is greater than 1%.
Type of Output Signal Choose among the options in Table 51.
Table 51: Type of Output Signal Option Description Maintained A single binary output is assigned. It will be energized when the
pump command is on and de-energized when the pump command is off.
Momentary Pulse
A pair of binary outputs are assigned. The start output will be energized momentarily when the pump command is on and the stop output will be energized momentarily when the pump command is off. A momentary output has a pulse duration of 1.5 seconds.
Is Outdoor Air Lockout of Cooling Needed? Choose among the options in Table 52.
Table 52: Is Outdoor Air Lockout of Cooling Needed? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes All cooling control strategies may be locked out. The cooling
lockout can be initiated from a controller input, or over the N2 Bus by a FMS.
AHU Applications Application Note 102
Select the Method to Initiate Cooling Lockout Choose among the options in Table 53.
Table 53: Select the Method to Initiate Cooling Lockout Option Description Software (N2) Command
A binary data point is provided to initiate the cooling lockout (Figure 69). If communication is lost with the FMS, the controller will maintain the last commanded state for ten minutes. The default of the cooling lockout is off.
Hardware AI Point
An analog input is assigned for an outside air temperature sensor. When the outside air temperature is below the cooling lockout setpoint, the cooling will be locked out; when the outside air temperature is above the setpoint plus the differential, the cooling will be enabled. If the analog input becomes unreliable, the cooling failsoft is enabled.
Both with AI Backup
A binary data point is provided to initiate the cooling lockout. If communication is lost with the FMS, the controller will use the outside air sensor as a backup for the cooling lockout decision. If the analog input becomes unreliable, the cooling failsoft is enabled. In the event N2 communications is lost when the outside air temperature is below the cooling lockout setpoint, the cooling will be locked out; when the outside air temperature is above the setpoint plus the differential, the cooling will be enabled. If the analog input becomes unreliable, the cooling failsoft is enabled.
CoolingLockout
N2 Command
Outdoor Air TemperatureCooling Lockout Setpoint
Differential
Compare
CoolingLockout
Outdoor Air TemperatureCooling Lockout Setpoint
Differential
Compare
N2 Command withAI Backup
AI Switch
N2 Command Status
N2 Command
CoolingLockout
Command
CLGLOCK
Figure 69: Lockout
AHU Applications Application Note 103
If the Control Sensor Becomes Unreliable, the Cooling Valve is Commanded To Choose among the options in Table 54.
Table 54: If the Control Sensor Becomes Unreliable, the Cooling Valve is Commanded To Option Description 0% Drive the valve to the 0% open position. 100% Drive the valve to the 100% open position. Last Reliable Command
Hold the output at the last reliable position.
Sequencer - Number of Stages See the Key Concepts section for a description of these options.
Is Vernier Control Needed? (AO Control for % Control Between Stages) Choose among the options in Table 55.
Table 55: Is Vernier Control Needed? (AO Control for % Control Between Stages) Option Description No No point/parameter assignment or logic sequence for this
selection. Yes This strategy allows an analog output to be commanded from 0 to
100% between each stage of cooling. The analog command increases from 0 to 100% as the sequencer cooling command from the control strategy increases from 0 to the starting point of the first stage. When you select Vernier control, the starting point of the first stage defaults to the normal proportional division of the number of stages plus one (i.e., 3 stages would start at 25, 50, and 75% commands). When the sequencer command rises above the first stage on percent, the analog command begins again at 0 and increases to 100% until the sequencer command equals the starting point of the second stage. The analog output operation between each stage is consistent between all stages. The Vernier control strategy cannot be used with rotational sequencing.
AHU Applications Application Note 104
Is Rotational Sequencing Needed? Choose among the options in Table 56.
Table 56: Is Rotational Sequencing Needed? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes The rotational sequencing option allows each stage to be the next
started (in order) after the controller turns off the first stage. For example, if Stages 1 - 2 - 3 – 4 energize and then turn off in the opposite order, the next sequence is 2 - 3 - 4 - 1. This new order de-energizes in reverse, and then reorders as 3 - 4 - 1 - 2. When you select the rotational sequencing feature, you cannot use Vernier control.
If the Control Sensor Becomes Unreliable Command Cooling Stages To Choose among the options in Table 57.
Table 57: If the Control Sensor Becomes Unreliable Command Cooling Stages To Option Description 0% Turn all stages off. 100% Turn all stages on. Last Reliable Command
Hold the staged outputs at the last reliable command.
Type of Output Signal (2-Position Valve) Choose among the options in Table 58.
Table 58: Type of Output Signal (2-Position Valve) Option Description Maintained A single binary output is assigned. It will be energized when the
valve is commanded open and de-energized when the valve is commanded closed.
Momentary Pulse
A pair of binary outputs are assigned, the open output will be energized momentarily when the valve is commanded open and the close output will be energized momentarily when the valve is commanded closed. A momentary output has a pulse duration of 1.5 seconds.
AHU Applications Application Note 105
Should the Cooling Command Go to 0% on Shutdown? Choose among the options in Table 59.
Table 59: Should the Cooling Command Go to 0% on Shutdown? Option Description Yes When the Shutdown mode is on, the controlled device will be
commanded to 0%. Use Loss of Airflow Defaults
The Shutdown mode will have no effect on the controlled device. Shutdown will turn the fan off causing the loss of airflow. The position of the controlled device will be determined by how the Loss of Air Flow question is answered.
Upon Loss of Air Flow, the Cooling Face and Bypass Damper will be Commanded To Choose among the options in Table 60.
Table 60: Upon Loss of Air Flow, the Cooling Face and Bypass Damper will be Commanded To Option Description 0% Drive the damper to the 0% face position and turn valve off. 100% Drive the damper to the 100% face position and turn the valve on. Remain In Control
Continue to control as normal. This strategy is intended to be used only where the coil has an effect on the sensor when airflow is off, that is the sensor is in close proximity to the coil.
If the Control Sensor Becomes Unreliable, the Cooling Face and Bypass Damper is Commanded To Choose among the options in Table 61.
Table 61: If the Control Sensor Becomes Unreliable, the Cooling Face and Bypass Damper is Commanded To Option Description 0% Drive the damper to the 0% face position and turn valve off. 100% Drive the damper to the 100% face position and turn the valve on. Last Reliable Command
Hold the output at the last reliable position and commands.
AHU Applications Application Note 106
Completing the Dehumidification Question/Answer Path To complete the dehumidification question/answer path: 1. Answer the questions as they are presented (Figure 70), using the
information presented in the Key Concepts section and the remainder of this procedure as a guide.
2. After the Dehumidification section, the question/answer path continues on to the Humidification section.
Select the dehumidification control strategy
None High signal selectionw/ cooling command
Addition of dehumidificationand cooling command
Select the humiditysensor for dehumidification
To Humidification
Section
Zone Return/Exhaust Air
Is dehumidification needed duringunoccupied mode?
No Yes
If the humidity sensor becomes unreliable, dehumid command =
0% Last reliablecommand
DEHUMID
Figure 70: Dehumidification
AHU Applications Application Note 107
Select the Dehumidification Control Strategy Choose among the options in Table 62.
Table 62: Select the Dehumidification Control Strategy Option Description None No point/parameter assignment or logic sequence for this
selection. High Signal Selection w/Cooling Command
See the Key Concepts section for a description of this option.
Addition of Dehumid. and Cooling Command
See the Key Concepts section for a description of this option.
Select the Humidity Sensor for Dehumidification Choose among the options in Table 63.
Table 63: Select the Humidity Sensor for Dehumidification Option Description Zone An analog input for a zone humidity sensor is defined. Return/ Exhaust Air
An analog input for a duct insertion return/exhaust air humidity sensor is defined.
Is Dehumidification Needed During Unoccupied Mode? Choose among the options in Table 64.
Table 64: Is Dehumidification Needed During Unoccupied Mode? Option Description No Dehumidification will only be active in the Occupied mode of
operation. Yes When Dehumidification is in use during the Unoccupied mode of
operation, the control output can be commanded above 0% open only during periods of positive supply airflow.
AHU Applications Application Note 108
If the Humidity Sensor Becomes Unreliable, Dehumid. Command = Choose among the options in Table 65.
Table 65: If the Humidity Sensor Becomes Unreliable, Dehumid. Command = Option Description 0% Dehumidification command goes to 0%. Last Reliable Command
Hold the command at the last reliable value.
AHU Applications Application Note 109
Completing the Humidification Question/Answer Path To complete the humidification question/answer path: 1. Answer the questions as they are presented (Figure 71), using the
information presented in the Key Concepts section and the remainder of this procedure as a guide.
2. After the Humidification section, the question/answer path continues on to the Modes of Operation section.
None
To Modes ofOperation
Section
Select humidification control strategy:
Staged Modulated
SEQUENCER: Number of stages
One through Nine
Select the setpoint type
Single humidificationsetpoint
% RH setpoint resetby outdoor air temp.
Select the humidity sensor for humidification
Zone Return/Exhaust air
Is humidification needed duringunoccupied mode?
No Yes
HUMID
Figure 71: Humidification
AHU Applications Application Note 110
Select the Humidification Control Strategy Choose among the options in Table 66.
Table 66: Select the Humidification Control Strategy Option Description None No point/parameter assignment or logic sequence for this
selection. Staged As the control humidity decreases below the user defined setpoint
and into the humidification proportional band, the controller calculates a 0 to 100% command. Staged humidification requires parameter inputs for cycle, interstage, and minimum on/off timers. Vernier and rotational sequencing is not available for staged humidification outputs. Adding integration to a control loop with staged outputs is not advised, as it usually results in the constant cycling of the outputs.
Modulated The system controls the modulated humidity (i.e., steam) coil based on the provided humidity sensor (Figure 72). As the control humidity decreases below the user defined setpoint and into the humidification proportional band, the controller issues a 0 to 100% command to the humidification device. During PI control, if the humidity sensor value is within the deadband area, the error is considered 0 and the control output holds constant. In proportional only control, if the sensor value is within the deadband area, the output command is 0%.
ABO6
Purge Vent
Shutdown
FailSoft
Humidity AIHumidification Setpoint
Proportional BandIntegrationDeadband
Offset
PI Control
Outdoor Temperature AI Outdoor Low Limit
Outdoor Reset BandHumidification Low Limit
Humidification Reset Band
Humidity Reset
HumidityIntegration
AO0
0
0 0
1 orOccupied
12
12
0
Shutdown
0
0
AND
Supply AirflowSupply Fan
Figure 72: Modulated Humidification Reset from Outside Air Temperature
Sequencer - Number of Stages See the Key Concepts section for a description of these options.
AHU Applications Application Note 111
Select the Setpoint Type Choose among the options in Table 67.
Table 67: Select the Setpoint Type Option Description Single Humidification Setpoint
A single humidification setpoint is used for humidification control. The value entered for the humidity deadband is active equally above and below the setpoint.
% RH Setpoint Reset by Outdoor Air Temp.
The outdoor air reset schedule performs a direct readjustment of the humidification setpoint. As the outdoor air temperature decreases, the humidification setpoint also decreases. The reset schedule is configured through the humidity low limit and reset band. It is associated with the outdoor air low limit and reset band.
Select the Humidity Sensor for Humidification Choose among the options in Table 68.
Table 68: Select the Humidity Sensor for Humidification Option Description Zone An analog input for a zone humidity sensor is defined. Return/ Exhaust Air
An analog input for a duct insertion return/exhaust air humidity sensor is defined.
Is Humidification Needed During Unoccupied Mode? Choose among the options in Table 69.
Table 69: Is Humidification Needed During Unoccupied Mode? Option Description No Humidification will only be active in the Occupied mode of
operation. Yes When humidification is in use during the Unoccupied mode of
operation, the control output can be commanded above 0% open only during periods of positive supply airflow.
Completing the Modes of Operation Question/Answer Path To complete the modes of operation question/answer path: 1. Answer the questions as they are presented (Figure 73), using the
information presented in the Key Concepts section and the remainder of this procedure as a guide.
2. After the Modes of Operation section, the question/answer path continues on to the Fan System Control section.
AHU Applications Application Note 112
Select the unoccupied control strategy:
None Intermittent night operation from zone
Select the method to control the occupied/unoccupied mode of operation:
Software(N2) command
Hardware BI point
Both withBI backup
Both can activate
Should a default occ/unocc schedule
take effect when the N2 is disconnected?
No Yes
How is shutdown mode initiated?
Should a default shutdown schedule
take effect when the N2 is
disconnected?
No Yes
Setup/setbackof htg/clg setpts
in main seqoperation from zone*
* only in room
controlstrategy
How is warmup/cooldown initiated?
No warmup/cooldown needed
Power fail restart logic?
No Yes
UNOCC
To Fan System
ControlSection
How is shutdown mode initiated?
Should a default shutdown schedule
take affect when the N2 is
disconnected?
No Yes
Software(N2) command
Hardware BI point
Both withBI backup
Both can activate
Software(N2) command
Hardware BI point
Both withBI backup
Both can activate
Software(N2) command
Hardware BI point
Both withBI backup
Both can activate
Figure 73: Modes of Operation
AHU Applications Application Note 113
Select the Unoccupied Control Strategy Choose among the options in Table 70.
Table 70: Select the Unoccupied Control Strategy Option Description None No point/parameter assignment or logic sequence for
this selection. The controller always operates in Occupied mode and only shuts down through Shutdown mode. HVAC PRO does not display questions for warmup/cooldown since this is an unoccupied feature.
Intermittent Night Operation from Zone Sensor
See the Key Concepts section for a description of this option.
Setup/Setback of Htg/Clg Setpts in Main Seq Operation from Zone (Only in Room Control Strategy)
See the Key Concepts section for a description of this option.
AHU Applications Application Note 114
Select the Method to Control the Occupied/Unoccupied Mode of Operation Choose among the options in Table 71.
Table 71: Select the Method to Control the Occupied/Unoccupied Mode of Operation Option Description Software (N2) Command
An occupied binary data point is provided for a facility management system to command. A default/backup time schedule in the controller takes effect when loss of communication with a supervisory device occurs. The time schedule follows occupied start and stop time parameters based on the controller’s internal clock. The controller’s clock is not battery backed and will reset to 00:00 hours whenever the controller resets, such as occurs after a power failure. Only a supervisory device (Companion/Facilitator, NCM, or ZT) can set the controller’s clock. When both start and stop time parameters are set to the same value, occupied remains on in standalone. If the backup schedule is not used and communication loss with a supervisory device occurs, the controller will maintain the last commanded state for ten minutes and then default the Occupied mode as on.
Hardware BI Point
A hardware binary input is provided to switch the controller between Occupied and Unoccupied modes. When the contact is closed, occupied status is on.
Both with BI Backup
An occupied binary data point is provided for a facility management system to command. If communication with the FMS is lost, the status of the binary input is used to determine Occupied mode.
Both can Activate
An occupied binary data point is provided for a facility management system to command. A hardware binary input is also provided to switch the controller between Occupied and Unoccupied modes. Either point can place the controller into the Occupied mode. Both points must be off for the controller to be in the Unoccupied mode.
AHU Applications Application Note 115
How is Shutdown Mode Initiated? Choose among the options in Table 72.
Table 72: How is Shutdown Mode Initiated? Option Description Software (N2) Command
A shutdown binary data point is provided for a facility management system to command. If the backup schedule is not used and communication loss with a supervisory device occurs, the controller will maintain the last commanded state for ten minutes and then default to Occupied mode as on.
Hardware BI Point
A hardware binary input is provided to switch the controller into the Shutdown mode. When the contact is closed, the Shutdown mode is on.
Both with BI Backup
A shutdown binary data point is provided for a facility management system to command and a hardware binary input is provided for backup. If communication with the FMS is lost, the status of the binary input is used to determine Shutdown mode.
Both can Activate
A shutdown binary data point is provided for a facility management system to command. A hardware binary input is also provided to switch the controller into Shutdown mode. Either point can place the controller into the Shutdown mode. Both points must be off for the controller to turn Shutdown mode off. When shutdown is enabled, all outputs to fans are turned off and the economizer dampers are closed. Preheat, heating, and cooling outputs will be shutdown to 0% command if the user specified they be affected by shutdown. Otherwise, they will go to their “loss of airflow position”. In Shutdown mode, all integration timers are set to 0, so no windup occurs when the system is put back into control.
AHU Applications Application Note 116
Should a Default Shutdown Schedule Take Effect When the N2 is Disconnected? Choose among the options in Table 73.
Table 73: Should a Default Shutdown Schedule Take Effect When the N2 is Disconnected? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes A default/backup time schedule in the controller takes effect when
loss of communication with a supervisory device occurs. The time schedule follows shutdown start and stop time parameters based on the controller’s internal clock. The controller’s clock is not battery backed and will reset to 00:00 hours whenever the controller resets, such as occurs after a power failure. Only a supervisory device (Companion/Facilitator, NCM, or ZT) can set the controller’s clock. When both start and stop time parameters are set to the same value, shutdown remains on in standalone. If the backup schedule is not used and communication loss with a supervisory device occurs, the controller will maintain the last commanded state for ten minutes and then default the Shutdown mode as off.
How is Warmup/Cooldown Initiated? Choose among the options in Table 74.
Table 74: How is Warmup/Cooldown Initiated? Option Description No Warmup/Cooldown Mode Needed
No point/parameter assignment or logic sequence for this selection.
Software (N2) Command
A warmup/cooldown binary data point is provided for a facility management system to command. If communication is lost with the FMS, the controller will maintain the last commanded state for ten minutes. The default of the Warmup/Cooldown mode is off.
Hardware BI Point
A hardware binary input is provided to switch the controller into the Warmup/Cooldown mode. When the contact is closed, the Warmup/Cooldown mode is on.
Both with BI Backup
A warmup/cooldown binary data point is provided for a facility management system to command and a hardware binary input is provided for backup. If communication with the FMS is lost, the status of the binary input is used to determine warmup/cooldown mode.
Both can Activate
A warmup/cooldown binary data point is provided for a facility management system to command. A hardware binary input is also provided to switch the controller into Warmup/Cooldown mode. Either point can place the controller into the Warmup/Cooldown mode. Both points must be off for the controller to turn Warmup/Cooldown mode off.
AHU Applications Application Note 117
Power Fail Restart Logic?
ShutdownCommand
Shutdown
ORNOT
B010B
DelayOnRestart Delay Time
Controller Reset Trigger
Figure 74: Power Fail Restart Choose among the options in Table 75.
Table 75: Power Fail Restart Logic? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes A power fail restart delay time delays the startup of the unit after a
power failure or controller reset condition. This logic holds the controller in Shutdown mode until the restart timer expires. This strategy prevents the startup of multiple controllers upon the restoration of power. When power is restored to the controller, the reset trigger is initially equal to 0. This results in shutdown being on. When reset completes, the reset trigger is equal to on. This causes a delay before shutdown is commanded back to off.
Completing the Fan System Control Question/Answer Path To complete the fan system control question/answer path: 1. Answer the questions as they are presented (Figure 75), using the
information presented in the Key Concepts section and the remainder of this procedure as a guide.
2. The Fan System Control section is the final portion of the question/answer path. You have completed the AHU applications question and answer path.
AHU Applications Application Note 118
Select the fan system control type:
Single Supply fan, w/static press cntl
Single sup/ret vol match w/stat pres ctl
Single supply, low/high speed
control
Constant volume
Is low static selection between
two sensors needed?
No Yes
Is ramp control upon supply fan startup needed?
No Yes
Is supply flow needed from an air flow measuring
station?
No Yes
Select the type of air flow
measurement:
Pitot tube
Scaled input-air flow station thermistor
Should the supply/return fan be commanded "OFF" upon a loss of air flow?
No Yes
Maintained Momentary Pulse
Type of output signal (supply) :
Is an alternate flow differential setpoint required for unocc'd or warmup modes?
No Yes
Is low static selection between
two sensors needed?
No Yes
Is ramp control upon supply fan startup needed?
No Yes
Is supply flow needed from an air flow measuring
station?
No Yes
Select the type of air flow
measurement:
Pitot tube
Scaled input-air flow station thermistor
FANSYSE
Figure 75: Fan System Control
AHU Applications Application Note 119
Will the controller start and stop the return fan?
No Yes
Select which fan should start first:
Supply Return
Type of output signal (return) :
Maintained Momentary Pulse
DONE
E
FANSYS
Figure 76: Fan System Control (Cont.)
Select the Fan System Control Type Choose among the options in Table 76.
Table 76: Select the Fan System Control Type Option Description Single Supply Fan with Static Press. Cntl
See the Key Concepts section for a description of this option.
Single Sup/Ret Vol Match w/Static Press Cntl
See the Key Concepts section for a description of this option.
Single Supply, Low/High Speed Control
See the Key Concepts section for a description of this option.
Constant Volume See the Key Concepts section for a description of this option.
AHU Applications Application Note 120
Is Low Static Selection Between Two Sensors Needed? Choose among the options in Table 77.
Table 77: Is Low Static Selection Between Two Sensors Needed? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes Two static pressure sensors can be selected for the AHU
controller configuration. The lowest static pressure value is in use as the input to the static pressure PID control loop.
Is Ramp Control Upon Supply Fan Startup Needed? Choose among the options in Table 78.
Table 78: Is Ramp Control Upon Supply Fan Startup Needed? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes A ramp step, in percent per second, is a user adjustable
parameter. When the static pressure setpoint is obtained during the ramp routine, the PID loop internal integration value will be set equal to the ramp signal offset and the ramp will end. This will provide a smooth transition from the ramp routine to PID control. For example, to achieve 30% command in ten minutes calculate the ramp step as follows: 10 min x 60 secs = 600 seconds 30% ÷ 600 secs = 0.05% per second, so the ramp step is 0.05% Note: If the fan status is not on by the time the step reaches
setpoint, the fan output will go to 0% and the ramp will restart.
AHU Applications Application Note 121
WITHRAMP
0
0
Static Pressure
StaticIntegrationTerm
FailSoft
0
MINSelect
Static Pressure 1Static Pressure 2
Supply Fan Cmd
ORDelayOFF
SupplyAirflow
Stored Integration
ANDCOMPARE>
Static Setpoint
Ramp Status
RAMP0
Supply Ramp Step
SUBStatic Offset
Ramp
Process VariableSetpoint
Proportional BandIntegrationDerivative
OffsetDeadband
AOSupply FanControl
Figure 77: Single Supply Fan, Static Pressure, with Ramp Control
RFMSSFRN
0
0
ReturnVolumeIntegrationTerm
FailSoft
0
Return Fan Cmd
ORDelayOFFReturn Airflow
CFMCalculation
Supply VolumeVelocity Pressure SUB
Return Fan Offset
Supply Ramp StatusON = Ramping
When supply fan ramp is chosen:
When supply fan ramp is not chosen:
XORDelayON
Return FanCommand
Unocc CFM Differential
Occupancy
Occ CFM Differential
Process VariableSetpoint
Proportional BandIntegrationDerivative
OffsetDeadband
AOReturn FanControl
CFMCalculation
Return Volume Velocity Pressure
Duct Area
Duct Area
Figure 78: Single Supply/Return Fan, Volume Matching, with Ramp Control
AHU Applications Application Note 122
Is Supply Flow Needed from an Air Flow Measuring Station? Choose among the options in Table 79.
Table 79: Is Supply Flow Needed from an Air Flow Measuring Station? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes Supply airflow in CFM is calculated for monitoring purposes only.
Select the Type of Air Flow Measurement Choose among the options in Table 80.
Table 80: Select the Type of Air Flow Measurement Option Description Pitot Tube This selection is required when the controller needs to calculate
the square root of the velocity pressure reading. The area of the face of the airflow station is required, and a constant is required to extract any amplification of the velocity pressure that is present in the design of the Pitot tube traverse. The formula for the CFM calculation of the Pitot tube method is shown in Figure 79.
Airflow Station (Thermistor)
This selection is intended for a packaged airflow station having a linear output ranged in velocity (FPM) or volume (CFM). In cases where the airflow station outputs a linear CFM signal, adjust the value for the area of the airflow measuring station to 1.0. CFM = (V)(A) Where: V = velocity (ft/min) A = area of the airflow station (sq ft)
BO11A
Supply Velocity PressureDuct AreaConstant
CFMCALC
CFM
CFM = (4005) (Pv/K) (A) Where: Pv = velocity pressure (in. WG)
K = constant (provided by the device manufacturer)A = area of the airflow station (sq ft)
MULTIPLY CFM
BO11B
Velocity(ft/min)
Duct Area
Figure 79: CFM Calculations
AHU Applications Application Note 123
Is an Alternate Flow Differential Setpoint Required for Unocc’d or Warmup Modes? Choose among the options in Table 81.
Table 81: Is an Alternate Flow Differential Setpoint Required for Unocc’d of Warmup Modes? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes The CFM differential can be adjusted to a different value
(typically 0) for unoccupied operation.
Type of Output Signal (Supply) Choose among the options in Table 82.
Table 82: Type of Output Signal (Supply) Option Description Maintained A single binary output is assigned. It will be energized when the
fan command is on and de-energized when the fan command is off.
Momentary Pulse
A pair of binary outputs are assigned. The start output will be energized momentarily when the fan command is on and the stop output will be energized momentarily when the fan command is off. A momentary output has a pulse duration of 1.5 seconds.
Should the Supply/Return Fan be Commanded “OFF” Upon a Loss of Air Flow? Choose among the options in Table 83.
Table 83: Should the Supply/Return Fan be Commanded “OFF” Upon a Loss of Air Flow? Option Description No If airflow interlock is selected and airflow is lost, the controller will
leave the fan command on and will still give airflow status indication and airflow failure alarm.
Yes When airflow is lost, after a user adjustable delay, the fan alarm will go on and the fan command will be turned off. The occupied or Warmup/Cooldown mode must toggle on, or the shutdown must toggle off to trigger another start command to the fan. Also, if the airflow status is toggled on, a start command will be issued and the fan alarm will clear.
AHU Applications Application Note 124
Will the Controller Start and Stop the Return Fan? Choose among the options in Table 84.
Table 84: Will the Controller Start and Stop the Return Fan? Option Description No No point/parameter assignment or logic sequence for this
selection. Yes The controller will start and stop the return fan in sequence with
the supply fan. A user-adjustable fan delay time is loaded in the supply fan parameters list. This is the time between the start commands of the supply fan and the return fan.
Type of Output Signal (Return) Choose among the options in Table 85.
Table 85: Type of Output Signal (Return) Option Description Maintained A single binary output is assigned. It will be energized when the
fan command is on and de-energized when the fan command is off. Supply fan airflow status triggers the start and stop commands to the return fan.
Momentary Pulse
A pair of binary outputs are assigned. The start output will be energized momentarily when the fan command is on and the stop output will be energized momentary when the fan command is off. A momentary output has a pulse duration of 1.5 seconds. Supply fan airflow status triggers the start and stop commands to the return fan.
Select Which Fan Should Start First Choose among the options in Table 86.
Table 86: Select Which Fan Should Start First Option Description Supply or Return
When selecting the supply and return fan start/stop, the user can select if the return or the supply fan will start first. It may be necessary to start the return fan first. This strategy could prevent damage to ductwork, or avoid a low temperature switch from dropping out the supply fan starter circuit due to excessively low ambient outside air during startup by pressurizing the mixed air temperature plenum with warmer return air.
AHU Applications Application Note 125
Troubleshooting Downloading an AHU Application
The following concerns problems that may be encountered when downloading an AHU assembled at HVAC PRO Release 4.00 or 5.00. Note: This overflow is only likely to occur on a very limited
number of jobs. Do not let this hamper the upgrade of your AHU jobs to HVAC PRO Release 5.00.
Table 87: Troubleshooting AHU Controllers Error/Condition Problem Solution Large Configurations Overflow the Amount of Configuration Space in the AHU Memory
Due to the enhancements/improvements made in the AHU paths since HVAC PRO Release 3.0, some large configurations may overflow the amount of configuration space in the AHU memory. The problem affects AHU revisions C05 or earlier. The user will not be informed that the program is too large, and the following symptoms can occur: • The AHU, after the download,
resets continually. • The Binary Inputs no longer
update their actual condition.
If you experience one of the symptoms described in the Problem column after downloading the AHU, perform the following: 1. Download the file AHU500.EXE from the Main
Board of the Bulletin Board System. This file is self-extracting and will give you
three files: AHUASM.EXE, FIXRESET.EXE and README.TXT.
2. Perform the steps in the README file to fix the reset problem.
3. Download the AHU with your original program created with an earlier release of HVAC PRO.
If you are upgrading your AHU programs or configuring a new AHU with HVAC PRO Release 5.00, perform the following: 1. Download the file AHU500.EXE from the Main
Board of the Bulletin Board System. This file is self-extracting and will give you
three files: AHUASM.EXE, FIXRESET.EXE and README.TXT.
2. Assemble your AHU configuration with HVAC PRO Release 5.0.
This new assembler will generate an error message Configuration Data Overflow if the file you are assembling will overflow the AHU memory. The object code necessary for download will not be created.
3. If your AHU configuration generates this message, re-configure and download at HVAC PRO Release 3.03.
AHU Applications Application Note 126
Saving an AHU Application File for a UNT Controller When using the Save As command to save a configuration to a different target device, all available devices should appear in the Devices window. If the Devices window reads No Target Device, look in the Reason Not Allowed: at the bottom of the screen for the reason. The most common reasons are provided below, along with suggested solutions for these issues. No Target Device is a valid option to save a configuration temporarily until you decide which option is best for your application. Note: It is not possible to load a UNT application into an AHU or
VAV (Variable Air Volume controller). It is not possible to load an AHU application into a VAV.
Table 88: Reasons for No Target Device Message Reason Solutions The device UNT1nn-n does not have enough AIs.
• Move the AIs up into the first six AIs if possible.
• Eliminate a feature that uses an AI. The device UNT1nn-n does not have enough AOs.
• Move the voltage AOs up into the first two AOs.
• Change the AO device type to a Zone Bus, and move it to AO-3 or greater.
The device UNT1nn-n does not have enough BIs.
Eliminate a feature that uses a BI.
The device UNT1nn-n does not support one of the AI sensors.
Change AI sensor types to Resistive or Voltage.
The device UNT1nn-n does not support one of the AO types.
Change AO device types to Voltage, Pneumatic, or Zone Bus.
AHU Applications Application Note 127
Point Assignments and Parameters Default Point Assignments
Table 89 provides the default point assignments for AHU applications.
Table 89: AHU Application Default Point Assignments Point Type Point Index Point Name AI 1st available Glycol Temp AI 1st available Heat Recov Temp AI 1st available Htg/Clg Sensor AI 1st available Minpos Vel Press AI 1st available OA Rel Humid AI 1st available Return Vel Press AI 1st available Return Velocity AI 1st available Supply Velocity AI 1 Outdoor Air Temp AI 2 Mixed Air Temp AI 3 Disch Air Temp AI 3 Hot Deck Temp AI 4 Cold Deck Temp AI 4 Zone Temp AI 5 Exhaust Temp AI 5 Minpos Velocity AI 5 Return Air Temp AI 6 Preheat Control AI 7 Coldest Zone AI 7 Rem Clg Setpoint AI 7 Static Press AI 7 Static Press #1 AI 7 Zone Rel Humid AI 8 Air Quality AI 8 Rem Htg Setpoint AI 8 Rem Zone Setpnt AI 8 Return Rel Humid AI 8 Static Press #2 AI 8 Supply Vel Press AI 8 Warmest Zone Continued on next page . . .
AHU Applications Application Note 128
Point Type (Cont.)
Point Index Point Name
BI 1st available Purge BI 1st available Return Airflow BI 1st available Supply Airflow BI 1st available Vent BI 2 Econ Switch BI 2 Occupied BI 2 Warmup/Cooldown BI 2 Summer/Winter BI 3 Shutdown AO 1st available Clg Face/Bypass AO 1st available Cooling Valve AO 1st available Cooling Vernier AO 1st available Heating Valve AO 1st available Heating Vernier AO 1st available Ht Recov Valve AO 1st available Htg Face/Bypass AO 1st available Htg/Clg Valve AO 1st available Humid Valve AO 1st available Min Damper Cmd AO 1st available Preheat Valve AO 1st available Preheat Vernier AO 1st available Preht Face/Bypass AO 1st available Return Fan Cntl AO 1st available Supply Fan Cntl AO 1 Damper Command AO 5 Humid Command AO 6 Preheat Command AO 7 Heating Command AO 8 Cooling Command AO 8 Preheat Control Continued on next page . . .
AHU Applications Application Note 129
Point Type (Cont.)
Point Index Point Name
BO 1st available Cooling Pump BO 1st available Cooling Pump BO 1st available Cooling Pump Off BO 1st available Cooling Stage 1 BO 1st available Cooling Stage 2 BO 1st available Cooling Stage 3 BO 1st available Cooling Stage 4 BO 1st available Cooling Stage 5 BO 1st available Cooling Stage 6 BO 1st available Cooling Stage 7 BO 1st available Cooling Stage 8 BO 1st available Cooling Stage 9 BO 1st available Cooling Valve BO 1st available Cooling Valve BO 1st available Cooling Valve Off BO 1st available Heating Pump BO 1st available Heating Pump BO 1st available Heating Pump Off BO 1st available Heating Stage 1 BO 1st available Heating Stage 2 BO 1st available Heating Stage 3 BO 1st available Heating Stage 4 BO 1st available Heating Stage 5 BO 1st available Heating Stage 6 BO 1st available Heating Stage 7 BO 1st available Heating Stage 8 BO 1st available Heating Stage 9 BO 1st available Heating Valve BO 1st available Heating Valve BO 1st available Heating Valve Off BO 1st available Ht Recov Pump BO 1st available Ht Recov Pump BO 1st available Ht Recov PumpOff BO 1st available Ht Recov Valve BO 1st available Htg Face/Bypass Continued on next page . . .
AHU Applications Application Note 130
Point Type (Cont.)
Point Index Point Name
BO 1st available Htg Face/Bypass BO 1st available Humid Stage 1 BO 1st available Humid Stage 2 BO 1st available Humid Stage 3 BO 1st available Humid Stage 4 BO 1st available Humid Stage 5 BO 1st available Humid Stage 6 BO 1st available Humid Stage 7 BO 1st available Humid Stage 8 BO 1st available Humid Stage 9 BO 1st available Min Damper Cmd BO 1st available Preheat Pump BO 1st available Preheat Pump BO 1st available Preheat Pump Off BO 1st available Preheat Stage 1 BO 1st available Preheat Stage 2 BO 1st available Preheat Stage 3 BO 1st available Preheat Stage 4 BO 1st available Preheat Stage 5 BO 1st available Preheat Stage 6 BO 1st available Preheat Stage 7 BO 1st available Preheat Stage 8 BO 1st available Preheat Stage 9 BO 1st available Preheat Valve BO 1st available Return Fan BO 1st available Return Fan BO 1st available Return Fan Off BO 1st available Supfan HI Off BO 1st available Supfan HI Speed BO 1st available Supfan HI Speed BO 1st available Supfan LO Off BO 1st available Supfan LO Speed BO 1st available Supfan LO Speed BO 1st available Supply Fan BO 1st available Supply Fan BO 1st available Supply Fan Off
AHU Applications Application Note 131
Default Parameters Table 90 provides the default parameters for AHU applications. Note: Values in parentheses are metric defaults.
Table 90: AHU Application Default Parameters Parameter Point
Location Default Value Description
Actual Cold Deck Setpt
ADF 18 calculated variable Actual cold deck setpoint being used
Actual Disch Clg Setpt ADF 18 calculated variable Actual discharge air cooling setpoint being used
Actual Disch Htg Setpt ADF 17 calculated variable Actual discharge air heating setpoint being used
Actual Disch Setpt ADF 17 calculated variable Actual discharge air setpoint being used Actual Hot Deck Setpt ADF 17 calculated variable Actual hot deck setpoint being used Actual Humid Setpt ADF 23 calculated variable Actual humidity setpoint Actual Mxd Air Setpnt ADF 24 calculated variable Actual mixed air setpoint Alt Clg Deadband ADF 146 0.0°C (0.0°F) Alternate cooling deadband when damper is
closed Cld Deck Low Lim ADF 144 12.0°C (55.0°F) Cold Deck Reset - cold deck low limit setpoint Cld Deck RBand ADF 145 11.0°C (20.0°F) Cold Deck Reset - cold deck reset band Cld Zone Hi Lim ADF 138 22.0°C (72.0°F) Hot Deck Reset - coldest zone low limit
setpoint Cld Zone RBand ADF 139 -2.0°C (-4.0°F) Hot Deck Reset - coldest zone reset band Clg % Stage 1 SP ADI 227 0.0% Percent command required for the first stage
to turn on Clg 2 Pos SP ADF 179 1% (1%) 2-position cooling valve setpoint Clg Lockout Cmd BD 205 0 = Off Cooling lockout command Clg Lockout Stat BD 22 0 = Off Cooling lockout status Clg OA Diff ADF 178 1.5°C (3.0°F) Cooling lockout OA differential Clg OA Setpoint ADF 177 12.0°C (55.0°F) Cooling lockout OA setpoint Coast Time ADF 252 10.0 Secute
(10.0 Sec) Coast time for two speed fan
Cold Deck DBand ADF 136 28.0°C (50.0°F) Deadband for the cold deck temperature loop Cold Deck Int Tm ADF 132 60 Integration time for the cold deck temperature
loop Cold Deck PBand ADF 137 16.0°C (30.0°F) Proportional band for the cold deck
temperature loop Cooling Command AO 8 Calculated value Cooling command Cooling Setpoint ADF 130 22.0°C (72.0°F) Zone Control - cooling setpoint Damper Duct Area ADF 157 0.4 sq m (4.0 sq ft) Minimum damper duct area for flow
calculation Damper Flow Mult ADF 158 1.00 Minimum damper flow constant for flow
calculation Deck Econ PBand ADF 133 28.0°C (50.0°F) Proportional band for the cold deck
economizer loop Continued on next page . . .
AHU Applications Application Note 132
Parameter (Cont.)
Point Location
Default Value Description
Default Econ SP ADF 150 20.0°C (68.0°F) Economizer switchover default OA dry bulb setpoint
Dehumid DBand ADF 182 0.0% RH Controller deadband for dehumidification loop Dehumid Int Tm ADF 181 0 Integration term for dehumidification loop Dehumid Offset ADF 184 0.0% RH Controller bias for dehumidification loop Dehumid PBand ADF 183 10.0% RH Proportional band for dehumidification loop Dehumid Setpoint ADF 180 50.0% RH Dehumidification setpoint Disch Clg DBand ADF 136 28.0°C (50.0°F) Deadband for the discharge cooling
temperature loop Disch Clg Int Tm ADF 139 60 Integration time for the discharge cooling loop Disch Clg LowLim ADF 142 12.0°C (55.0°F) Supply Air Reset - discharge cooling low
setpoint Disch Clg PBand ADF 141 16.0°C (30.0°F) Proportional band for the discharge cooling
temperature loop Disch Clg RBand ADF 143 11.0°C (20.0°F) Supply Air Reset - discharge cooling reset
band Disch Econ PBand ADF 133 28.0°C (50.0°F) Proportional band for the discharge
economizer loop Disch Htg DBand ADF 134 1.0°C (2.0°F) Deadband for the discharge heating
temperature loop Disch Htg DBand ADF 133 0.0°C (0.0°F) Heating deadband for constant discharge
temperature loop Disch Htg Int Tm ADF 138 60 Integration time for the discharge heating
loop Disch Htg LowLim ADF 144 24.0°C (75.0°F) Supply Air Reset - discharge heating low
setpoint Disch Htg LowLim ADF 144 12.0°C (55.0°F) Room Reset of Heating - discharge heating
low setpoint Disch Htg PBand ADF 140 33°C (60°F) Proportional band for the discharge heating
temperature loop Disch Htg RBand ADF 145 11.0°C (20.0°F) Supply Air Reset - discharge heating reset
band Disch Htg RBand ADF 145 22.0°C (40.0°F) Room Reset of Heating - discharge heating
reset band Disch Low Limit ADF 142 12.0°C (55.0°F) Supply Air Reset - discharge low setpoint Disch Reset Band ADF 143 22.0°C (40.0°F) Supply Air Reset - discharge reset band Discharge Setpnt ADF 129 42.0°C (60.0°F) Discharge air control - discharge setpoint Econ Status BD 19 0 = Off Economizer status ON = outdoor air cooling
available Econ Switch BD 199 0 = Off Economizer switchover command Econ Switch Diff ADF 151 1.0°C (2.0°F) Economizer switchover OA dry bulb
differential Econ Switch SP ADF 150 20.0°C (68.0°F) Economizer switchover OA dry bulb setpoint Enthalpy Diff SP ADF 151 0.5 KCl/Kg
(1.0 Btu/lb) Economizer switchover enthalpy differential
Exhaust Setpoint ADF 129 24.0°C (75.0°F) Exhaust Control - exhaust setpoint Continued on next page . . .
AHU Applications Application Note 133
Parameter (Cont.)
Point Location
Default Value Description
Exhst Clg Int Tm ADF 132 600 Integration time for the exhaust cooling temperature loop
Exhst Clg PBand ADF 137 8°C (15°F) Proportional band for the exhaust cooling temperature loop
Exhst Htg DBand ADF 134 0.5°C (1.0°F) Deadband for the exhaust heating temperature loop
Exhst Htg Int Tm ADF 131 600 Integration time for the exhaust heating temperature loop
Exhst Htg PBand ADF 135 -11°C (-20°F) Proportional band for the exhaust heating temperature loop
Fan Delay ADF 253 0.5 Minute Fan delay time Glycol Low Lim ADF 155 3.5°C (38.0°F) Heat Recovery - glycol low limit setpoint Glycol PBand ADF 156 22°C (40°F) Heat Recovery - glycol low limit prop band Glycol DBand ADF 153 0.0°C (0.0°F) Heat Recovery - glycol low limit deadband Glycol Int Tm ADF 154 90 Heat Recovery - glycol low limit integr. time Heating Command AO 8 Calculated value Heating command Heating Setpoint ADF 129 21.5°C (71.0°F) Zone Control - heating setpoint Hot Deck Int Tm ADF 131 60 Integration time for the hot deck temperature
control Hot Deck Low Lim ADF 140 24.0°C (75.0°F) Hot Deck Reset - hot deck low limit setpoint Hot Deck PBand ADF 135 -33°C (-60°F) Proportional band for hot deck temperature
control Hot Deck RBand ADF 141 11.0°C (20.0°F) Hot Deck Reset - hot deck reset band Hot Zone Hi Lim ADF 142 25.5°C (78.0°F) Cold Deck Reset - hottest zone high limit
setpoint Hot Zone RBand ADF 143 3.5°C (-6.0°F) Cold Deck Reset - hottest zone reset band Ht Recov DBand ADF 154 0.0°C (0.0°F) Controller deadband for the heat recovery
temperature loop Ht Recov Diff ADF 151 2.5°C (5.0°F) Heat recovery differential Ht Recov Int Tm ADF 152 90 Integration time for the heat recovery
temperature loop Ht Recov Offset ADF 153 0.0% Controller bias for the heat recovery
temperature loop Ht Recov PBand ADF 151 -22°C (-40°F) Proportional band for the heat recovery
temperature loop Ht Recov Setpnt ADF 150 1.5°C (35.0°F) Heat recovery ON setpoint Ht Recov Setpnt ADF 150 10.0°C (50.0°F) Heat recovery temperature loop setpoint Htg % Stage 1 SP ADI 226 0.0% Percent command required for the first stage
to turn on Htg 2 Pos SP ADF 175 1% 2-position heating valve setpoint Htg High Setpnt ADF 175 38.0°C (100.0°F) Summer winter switchover setpoint Htg High SP Diff ADF 176 22.0°C (40.0°F) Summer winter switchover differential Htg Lockout Cmd BD 204 0 = Off Heating lockout command Htg Lockout Stat BD 21 0 = Off Heating lockout status Htg OA Diff ADF 174 1.5°C (3.0°F) Heating lockout OA differential Continued on next page . . .
AHU Applications Application Note 134
Parameter (Cont.)
Point Location
Default Value Description
Htg OA Setpoint ADF 173 12.0°C (55.0°F) Heating lockout OA setpoint Humid Command AO 8 Calculated value Humidity command Humid Deadband ADF 187 0.0% RH Controller deadband for humidification loop Humid Int Tm ADF 186 0 Integration term for humidification loop Humid Low Lim SP ADF 190 20.0% RH Humidification low humidity setpoint Humid OA Low SP ADF 192 -23.0°C (-10.0°F) Humidification low OA setpoint Humid OA RBand ADF 193 22.0°C (40.0°F) Humidification OA reset band Humid Offset ADF 189 0.0% RH Controller bias for humidification loop Humid Prop Band ADF 188 -10.0% RH
(-10.0% RH) Proportional band for humidification loop
Humid Reset Band ADF 191 20.0% RH Humidification humidity reset band Humid Setpoint ADF 185 40.0% RH Humidity setpoint IAQ Low Limit ADF 153 800 ppm (800 ppm) Indoor air quality low limit setpoint IAQ Reset Band ADF 154 200 ppm (200 ppm) Indoor air quality reset band Indoor Air Quality ADF 21 Calculated value Indoor air quality actual setpoint Min Pos DBand ADF 160 0.0% Controller deadband for minimum flow loop Min Pos Int Tm ADF 159 20 Integration time for minimum flow loop Min Pos Offset ADF 162 0.0% Controller bias for minimum flow loop Min Pos PBand ADF 161 -140000 L/M
(-5000 CFM) Proportional control for minimum flow loop
Min Pos RBand ADF 155 10.0% (10.0%) Minimum position reset band Min Pos RBand ADF 155 28000 L/M
(1000.0 CFM) Minimum position reset band
Minduct_flow ADF 22 Calculated variable Minimum damper actual flow Minimum Pos ADF 156 57000 L/M
(2000 CFM) Minimum position setpoint
Minimum Pos ADF 156 15.0% Minimum damper minimum position setpoint Mxd Air Deadband ADF 244 0.0°C (0.0°F) Deadband for the mixed air loop Mxd Air Int Tm ADF 243 100 Integration term for mixed air control Mxd Air LL DBand ADF 242 0.0°C (0.0°F) Deadband for the mixed air low limit loop Mxd Air LL Int Tm ADF 241 80 Integration time for mixed air low limit Mxd Air LL Offst ADF 165 0.0°C (0.0°F) Minimum damper position for mixed air low
limit Mxd Air LL PBand ADF 164 -16.5°C (-30°F) Proportional band for the mixed air low limit
loop Mxd Air Low Lim ADF 163 7.0°C (45.0°F) Mixed air low temperature limit Mxd Air Propband ADF 245 33.0°C (50.0°F) Proportional band for the mixed air loop Mxd Air Setpoint ADF 246 13.0°C (55.0°F) Mixed air setpoint Night Clg Diff ADF 197 2.5°C (5.0°F) Unoccupied cooling differential Night Clg Setpnt ADF 196 27.5°C (82.0°F) Unoccupied cooling setpoint Night Htg Diff ADF 195 2.5°C (5.0°F) Unoccupied heating differential Night Htg Setpnt ADF 194 15.5°C (60.0°F) Unoccupied heating setpoint Continued on next page . . .
AHU Applications Application Note 135
Parameter (Cont.)
Point Location
Default Value Description
OA Enthalpy ADF 19 0.0 KCl/kg (0.0 Btu/lb)
Calculated outdoor air enthalpy
OA Enthalpy Diff ADF 152 0.5 KCl/kg (1.0 Btu/lb)
Economizer switchover OA enthalpy differential
OA Enthalpy SP ADF 151 14.0 KCl/Kg (25.0 Btu/lb)
Economizer switchover OA enthalpy setpoint
Occ Flow Diff ADF 215 57000 L/M (2000 CFM)
Occupied flow differential
Occ Start Time ADI 136 00:00 Hr:Mn Occupied start time Occ Stop Time ADI 137 00:00 Hr:Mn Occupied stop time Occupied Command BD 196 1 = Occ Occupied command. 0 = Unoccupied. Occupied Status BD 27 1 = Occ Occupied mode status. 0 = Unoccupied. Preheat Command AO 8 Calculated value Preheat command Preht % Stage 1 SP ADI 225 0.0% Percent command required for the first stage
to turn on Preht Deadband ADF 170 0.0°C (0.0°F) Controller deadband for preheat temperature
loop Preht F/B Diff ADF 169 2.5°C (5.0°F) Preheat face and bypass OA differential Preht F/B Setpnt ADF 168 1.5°C (35.0°F) Preheat face and bypass OA setpoint Preht Int Tm ADF 169 60 Integration time for preheat temperature loop Preht LLim Diff ADF 169 5.5°C (10.0°F) Preheat low limit OA differential Preht LLim SP ADF 168 10.0°C (50.0°F) Preheat low limit OA setpoint Preht Lock Cmd BD 203 0 = Off Preheat lockout command Preht Lock Stat BD 20 0 = Off Preheat lockout status Preht OA Diff ADF 167 2.5°C (5.0°F) Preheat OA differential Preht OA Setpnt ADF 166 12.0°C (55.0°F) Preheat OA setpoint Preht Offset ADF 172 0.0°C (0.0°F) Controller bias for preheat temperature loop Preht PBand ADF 149 -11.0°C (-20°F) Proportional band for preheat temperature
loop Preht Setpoint ADF 168 10.0°C (50.0°F) Preheat setpoint Purge Command BD 194 0 = Off Purge command Purge Status BD 31 0 = Off Purge mode status Restart Delay ADF 224 1.0 Minute Power fail restart delay Restart Status BD 26 0 = Off Restart status Ret Vol DBand ADF 209 0 L/M (0 CFM) Controller deadband for return volume flow
loop Ret Vol Deriv Wt ADF 212 0 Derivative weight for return volume flow loop Ret Vol Int Tm ADF 208 20 Integral time for return volume flow loop Ret Vol Offset ADF 211 0 L/M (0 CFM) Controller bias for return volume flow loop Ret Vol PBand ADF 210 +700000 L/M
(+25000 CFM) Proportional band for return volume flow loop
Retrn Clg DBand ADF 136 11°C (20°F) Deadband for the return cooling temperature loop
Retrn Clg Int Tm ADF 132 600 Integration time for the return air cooling loop Continued on next page . . .
AHU Applications Application Note 136
Parameter (Cont.)
Point Location
Default Value Description
Retrn Clg PBand ADF 137 8°C (15°F) Proportional band for the return cooling temperature loop
Retrn Econ PBand ADF 133 11°C (20°F) Proportional band for the return economizer loop
Retrn High Limit ADF 144 26.5°C (80.0°F) Supply Air Reset - return air high setpoint Retrn Htg DBand ADF 134 0.5°C (1.0°F) Deadband for the return heating temperature
loop Retrn Htg Int Tm ADF 131 600 Integration time for the return air heating loop Retrn Htg PBand ADF 135 -11°C (-20°F) Proportional band for the return heating
temperature loop Retrn Reset Band ADF 145 -4.5°C (-8.0°F) Supply Air Reset - return reset band Return Air Enthalpy ADF 20 0.0 KCl/kg
(0.0 Btu/lb) Calculated return air enthalpy
Return Duct Area ADF 200 2.3 sq m (25 sq ft) Return duct area Return Fan Alarm BD 25 0 = Normal Return fan alarm Return Flow ADF 26 Calculated value Return volume Return Flow Mult ADF 201 1.00 Return airflow multiplier Return Setpoint ADF 129 24.0°C (75.0°F) Return air control - return setpoint Shutdn Off Time ADI 139 00:00 Hr:Mn Shutdown off time Shutdn On Time ADI 138 00:00 Hr:Mn Shutdown on time Shutdown Command BD 197 0 = Off Shutdown command Shutdown Status BD 28 0 = Off Shutdown mode status Static Deadband ADF 204 0.0 Pa (0.0 in. WG) Controller deadband for static pressure loop Static Deriv Wt ADF 207 0 Derivative weight for static pressure loop Static Int Tm ADF 203 20 Integration time for static pressure loop Static Offset ADF 206 0.0 Pa (0.0 in. WG) Controller bias for static pressure loop Static Prop Band ADF 205 -1000.0 Pa
(-4.0 in. WG) Proportional band for static pressure loop
Static Setpoint ADF 202 250.0 Pa (1.0 in. WG)
Static pressure setpoint
Summer/Winter BD 23 0 = Summer Summer/Winter mode status Summer/Winter BD 198 0 = Summer Summer/Winter mode status Supply Duct Area ADF 198 2.3 sq m (25 sq ft) Supply duct area Supply Fan Alarm BD 24 0 = Normal Supply fan alarm Supply Flow ADF 25 Calculated value Supply volume Supply Flow Mult ADF 199 1.00 Supply airflow multiplier Supply Ramp Step ADF 213 0.33%/sec Ramp step for supply fan in percent. Used at
startup. Supply VP Diff ADF 201 2.50 Pa
(0.01 in. WG) Velocity pressure setpoint for two speed supply fan
Supply VP Setpnt ADF 200 7.50 Pa (0.03 in. WG)
Velocity pressure differential for two speed supply fan
Temp Diff Setpnt ADF 150 4.5°C (8.0°F) Economizer switchover temperature differential
Continued on next page . . .
AHU Applications Application Note 137
Parameter (Cont.)
Point Location
Default Value Description
Unocc Dis Clg SP ADF 143 15.5°C (60.0°F) Unoccupied discharge cooling setpoint Unocc Dis Htg SP ADF 142 32.0°C (90.0°F) Unoccupied discharge heating setpoint Unocc Econ PBand ADF 235 0.0°C (0.0°F) Unoccupied proportional band for the
economizer loop Unocc Flow Diff ADF 214 0 L/M (0 CFM) Unoccupied flow differential Unocc Setback ADF 148 4.5°C (8.0°F) Unoccupied setback Unocc Setup ADF 147 4.5°C (8.0°F) Unoccupied setup Vent Command BD 193 0 = Off Vent command Vent Status BD 30 0 = Off Vent mode status W/C Zone Diff ADF 130 2.2°C (4.0°F) Warmup/cooldown zone differential W/C Zone Setpnt ADF 144 22.0°C (72.0°F) Warmup/cooldown zone setpoint Warmup/Cooldown Command
BD 195 0 = Off Warmup command
Warmup/Cooldown Status
BD 29 0 Off (0 On) Warmup/cooldown status
X Preht PBand ADF 171 -33°C (-60°F) Proportional band for preheat temperature loop
Zone Clg DBand ADF 136 11°C (20°F) Deadband for the zone cooling temperature loop
Zone Clg Int Tm ADF 132 600 Integration time for the zone cooling loop Zone Clg PBand ADF 137 8°C (15°F) Proportional band for the zone cooling
temperature loop Zone Econ PBand ADF 133 11°C (20°F) Proportional band for the zone economizer
loop Zone Htg DBand ADF 134 0.5°C (1.0°F) Deadband for the zone heating temperature
loop Zone Htg Int Tm ADF 131 600 Integration time for the zone heating loop Zone Htg PBand ADF 135 -11°C (-20°F) Proportional band for the zone heating
temperature loop Zone Integration ADF 144 0 Integration time for zone temperature loop Zone Prop Band ADF 145 4.5°C (8.0°F) Supply Air Reset - proportional band for zone
reset loop Zone Setpoint ADF 129 22.0°C (72.0°F) Zone Control - zone setpoint
Controls Group 507 E. Michigan Street www.johnsoncontrols.comP.O. Box 423 Release 8.0Milwaukee, WI 53201 Printed in U.S.A.