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BUILDING AUTOMATION AND CONTROLSYSTEMS
SECTION V
WWHATHAT WWILLILL WWEE CCOVEROVER ?? ControlsControls
Basic Types Inputs & Outputs TechnologiesTechnologies
Pneumatic Electric DDC
Terminology PID Controls Review
Building Automation Systems for Energy Building Automation Systems for Energy ManagementManagement Basic Functions Programs Review
Section V - 2
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BBASICASIC TTYPESYPES
Manual Manual SwitchesSwitchesDimmers
Open Loop AutomaticOpen Loop AutomaticTimer
Cl d L A t tiCl d L A t tiClosed Loop AutomaticClosed Loop AutomaticThermostatHumidistatDimmable Ballast w/Photosensor
Section V - 3
BASIC FEEDBACK CONTROL SYSTEM
SET POINT RC
CONTROLLER
RC
T
CONTROLLEDDEVICE
SENSOR
ACTUATOR
AIR FLOW
HEATING COIL
Section V - 4
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BBASICASIC TTYPESYPES
Two Position Two Position The system is either OFF or ON (gas furnace). Accomplished with a relay whose contacts are either Accomplished with a relay whose contacts are either
open or closed, or a valve whose stem position is either open or closed.
Proportional Proportional A variation from the set point produces a proportional
movement in the actuator. Pneumatic controls vary the air pressure. Electric controls use a potentiometer (a type of
variable resistor).
Section V - 5
BBASICASIC IINPUTSNPUTS & O& OUTPUTSUTPUTS
Binary or Digital (D)Binary or Digital (D) Signal with two states or positions which can be
incremental (on-off, day-night, open-closed, occupied-unoccupied, series of 1’s & 0’s)
Analog (A)Analog (A) Signal can be monitored or controlled through a
f i i l (range of positions or values (0 to 50o C, 20 to 35 kPa, 0 to 10 VDC,4 to 20 milliamps)
Section V - 6
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Input ExamplesInput ExamplesAnalogAnalog DigitalDigital
Outside Air Temp. SensorAnalog Input
Low Temp. DetectorDigital Input
End SwitchDigital Input
Duct Smoke DetectorDigital Input
LANDIS & GYR
Room Temperature SensorAnalog Input
High Pressure DetectorDigital Input
Smoke Detector
Section V - 7
Input Points
Inputs & OutputsInputs & Outputs
pTemperature Relative HumidityFlow PressureStatus or Proof Air Quality
AIAI
AI / DIAI / DIAI / DIAI / DI
AIAIAIAIAIAI
Output PointsMotors for Pumps / Fans ValvesLights Dampers
DODO AOAODODO AOAOLights Dampers
Variable Speed Drives Lighting Contactors(or digital)
DODODODO AOAO
AOAO
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Inputs & OutputsInputs & Outputs
1.VFD Start/Stop
2.VFD Speed Signal
DOAO
Variable Air Volume Variable Air Volume SystemSystem
5.Static Press
4.High Static Cutout
3.Air Flow AIDI AI
Section V - 9
BBASICASIC TTECHNOLOGIESECHNOLOGIES
PneumaticPneumatic
ElectricElectric
Direct Digital Control (DDC)Direct Digital Control (DDC)
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PPNEUMATICNEUMATIC CCONTROLSONTROLS Use clean, dry, oil-free compressed aircompressed air to operate the control system. Have been used in many HVAC applications.
M ain A ir L ine
H ot W aterSupply
Air Com pressorC ontroller
A nalog Signal
B ranch A ir L ine
HC
O utside A ir
Supply A ir Sensor
H eatingC oil
Supply Fan
A nalog Signal
H ot W ater V alve
Section V - 11
PPNEUMATICNEUMATIC CCONTROLSONTROLS
AdvantagesAdvantages Are well understood by many designers and most
maintenance people maintenance people. Are inherently proportional and very reliable. Were relatively inexpensive in the past.
DisadvantagesDisadvantages Not very precise. Typically required frequent calibration. Pneumatic control algorithms are hard to change.
(typically pre-set by manufacturer)
Section V - 12
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EELECTRICLECTRIC CCONTROLSONTROLS
Can be analog electric or electronic controls. Use a variable, but continuous, electrical voltage or electrical voltage or
currentcurrent to operate the control system. Transmit signals
quickly and accurately.
Section V - 13
EELECTRICLECTRIC CCONTROLSONTROLS
AdvantagesAdvantages Can be very accurate and very stable. Do not require field calibration and are drift free if Do not require field calibration, and are drift-free, if
good quality sensors are used. Relatively easy to implement proportional plus
integral (PI) control electronically.
DisadvantagesDisadvantages Difficult to interchange parts easily because of the g p y
many different systems. Do not interface directly with our digital computers
Section V - 14
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DDIRECTIRECT DDIGITALIGITAL CCONTROLSONTROLS Use electrical pulseselectrical pulses to send signals. Interface directly with microprocessors, directly &/or via the
internet using TCP/IP.
Section V - 15
DDIRECTIRECT DDIGITALIGITAL CCONTROLSONTROLS
AdvantagesAdvantages Algorithms can be adjusted relatively easily after
installation Precise Precise No controller drift, recalibration is normally not
necessary Cost effective (similar to electronics market)
DisadvantagesDisadvantages Possibly not well understood by O&M staff Possibly not well understood by O&M staff Different communication protocols, interface
standards, and internal logic are typically complex (BACNET-ASHRAE 135-2008; and Lonworks – LonmarkCorporation; are both addressing these interface problems)
Section V - 16
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WWEBEB BBASEDASED EENERGYNERGY IINFORMATIONNFORMATION
ANDAND CCONTROLONTROL SSYSTEMSYSTEMS
TCP/IP is Transmission Control Protocol/Internet Protocol Internet Explorer, Netscape Navigator, Mozilla Firefox all take
TCP/IP iTCP/IP input Many submeters now have data accumulators that have URL
addresses, and send data by TCP/IP over Local Area Networks This data will come into your PC in standard spread sheet format
for you to use as you like You can make charts, graphs, tables, etc in Excel or other
common SS programs You now have your own web based energy information system And it doesn’t cost you a fortune. Save your money for the really
fancy analysis and diagnostic systems that many companies can provide to you
Section V - 17
CCONTROLONTROL AALGORITHMSLGORITHMS
PID Controls P is proportional I is integral I is integral D is derivative
Controls are usually P, PI or PID PID is considered the best of this group Newer control algorithms are:
Fuzzy logic Learning systems Self-optimizing systems
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PID Controls Loop ResponsePID Controls Loop Response
Section V - 19
Stability Stable if process doesn't show continuing trend away from setpoint or continuous oscillation following an upset in either load or setpoint
Loop DefinitionsLoop Definitions
PID ControlsPID Controls
Response Time
Time required for PV to reach SP following a step change in mode or setpoint
Overshoot The amount the PV goes beyond the SP following a change in load or setpoint
Offset The amount of constant error existing between PV and SP once the process reaches steady state
S li Ti Ti i d f t h t d t t f ll i h i l d t i tSettling Time Time required for process to reach steady state following a change in load or setpoint
Steady StateCondition that exists in closed loop system when the control variable (CV) equals a constant value and no oscillation occurs
Section V - 20
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CONTROL MODE PURPOSE ERROR DETECTIONS
Summary Of GainsSummary Of Gains
PID ControlsPID Controls
DETECTIONS
PG Reacts to Change Detects SIZE of Error
IG Reduces/Eliminates Offset Averages Error over TIME
S Hi h R t L dDG Senses High Rate Load Detects RATE of change of error
biasactiondt
errordDGactiondterror
IGactionerror
PGadjustableCV
*
)(
1000*
1000*
1000)(
Section V - 21
RREVIEWEVIEW::
CCONTROLSONTROLSCCONTROLSONTROLS
Section V - 22
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1. List advantages and disadvantages of pneumatic controls.
2. Why is DDC so popular?
3 What does the term “direct acting” mean?3. What does the term direct acting mean?
Section V - 23
4. The difference between the setting at which a controller operates to one position and the setting at which it changes to the other is known as the:
A) Throttling range B) OffsetC) Differential D) Control point
5. What is the flow rate of 16°C water through a control valve with a flow coefficient of 0.01 and a pressure difference of 100 kPa?
A) 0.1 LPS B) 0.2 LPSC) 0.6 LPS D) 0.4 LPS
Section V - 24
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BBUILDINGUILDINGAAUTOMATIONUTOMATIONSSYSTEMSYSTEMSSSYSTEMSYSTEMS
(BAS)(BAS)
Section V - 25
Floor Level Network
Building Level Network
Management Level Network
BAS AnatomyBAS Anatomy
Management Level Network
Remote System Access
Remote Alarm NotificationRemote Alarm Notification
Interoperability with other Buildings/Systems/Networks
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RECOMMENDED GOAL FOROPERATION OF NEW BAS’S
Single seat operation for the BAS using a common database for all operational and maintenance data database for all operational and maintenance data accessible in the facility.
This means that the Maintenance Management System and the Energy Management System(s), at the minimum, must share a common database.
Section V - 27
BBASICASIC FFUNCTIONSUNCTIONS
1.1. Monitoring/SurveillanceMonitoring/Surveillance• Building Conditions• Equipment Status• Equipment Status• Utility Submetering• Climatic Data• Fire & Security
BUILDING
2FacilityHVAC
3EnergyPower
4FactoryPower
5FactoryPower
and
6OfficePower
71st
FloorOffice
82nd
FloorOffice
9Computer
RoomPower
10Computer
RoomHVAC
11OfficeHVAC
1A. General Service Meter(Utility Meter for Billing)
1B. Electric Heat Meter(Utility Meter for Billing)
Lights Lights Lights and LightsHVAC
12OfficeRTU-1
13Office
RTU-13
14OfficeRTU-3
15OfficeRTU-4
19CAFE
20FactoryLights
24Air
Compressor
21Energy
MezzanineTest Room
22Elevator
23English
Labs
16Factory
RTU
17Factory
RTU
18Factory
RTU
Section V - 28
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BBASICASIC FFUNCTIONSUNCTIONS
2.2. Demand LimitingDemand Limiting• Load shedding• Duty cycling
3.3. MaintenanceMaintenance• Remote operation and control of equipment• Generation of maintenance schedules• Diagnosing breakdowns
4.4. Record GenerationRecord Generation• Trends and operation logsp g• Utility demand profile (“baseline”)• Modification/replacement analysis• Energy conservation documentation
Section V - 29
SSTARTTART--SSTOPTOP OOPTIMIZATIONPTIMIZATIONHow It WorksHow It Works
Start the equipment at the latest possible time Stop at the earliest possible time
G ( )ENERGY (KWH)SAVINGS
FROM SSTO
EM
AN
D (
KW
)
ENERGY (KWH)SAVINGS
FROM SSTO
DE
0 2018161412108642 22 24
OFF-PEAK$0.0453/KWH
OFF-PEAK$0.0453/KWH
PEAK$0.0759/KWH
OCCUPANCY PARTIALOCC
Section V - 30
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CCHILLEDHILLED WWATERATER RRESETESET IntroductionIntroduction
Many buildings’ chilled water setting is designed for the heaviest anticipated cooling load.
Significant cost savings can result from resetting chilled water Significant cost savings can result from resetting chilled water temperatures in anticipation of cooling load
How It WorksHow It Works When the load, chilled water T, or return chilled water
temperature increases, the chilled water setpoint is lowered, and vice versa
A one degree C increase in CWT makes the chiller about 2% more efficient
You must be able to meet both sensible and latent cooling loads. Also, there may be minimum flow condition on the chiller that limits this change.
Section V - 31
CCONDENSERONDENSER WWATERATER RRESETESET
The same idea can be used on the other side of the chiller by reducing the t t f th li t f th temperature of the cooling water from the cooling tower.
For every one degree C reduction in the temperature of the cooling water, the chiller efficiency goes up about 1.5 %.
Be careful with older chillers since they Be careful with older chillers, since they can not take too cold cooling water without developing head pressure problems.
Section V - 32
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SSUPPLYUPPLY AAIRIR RRESETESET
Supply Air Reset Based on LoadSupply Air Reset Based on Load A good rule of thumb provides for a supply air
t t t f f th th diff b t temperature reset for one-fourth the difference between the supply design temperature and the design space temperature
Savings CalculationDesignAirSupply
DesignAirSupplyTempDesiredLowestSAR
4
Where: Lowest Desired Temp is the temperature of the coolest room Supply Air Design is the current temperature of Supply Air
Section V - 33
SSTATICTATIC PPRESSURERESSURE RRESETESET How It WorksHow It Works
The DDC system monitors the VAV static pressure and lowers the pressure until only one damper is completely open
The Static Pressure and VFD control sensors must be located on the same DDC control panel
40% 50% 60%
7 5 % 1 0 0 % 7 0 %
Section V - 34
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SSTATICTATIC PPRESSURERESSURE RRESETSESETS•• Proof of PerformanceProof of Performance
– Operating the fan with zero airflow wastes energy– Modulating fan speed based on damper position reduces
fan usage and saves energy
2.5
2.0
1.5
ssu
re (
in. w
.g.)
No Reset
1.0
0.5
0.00 50% 100%
Sta
tic
Pre
s
Demand
Reset
Energy Savings
Section V - 35
EECONOMIZERCONOMIZER
•• How It WorksHow It Works– Reduce cooling & heating energy by optimizing mixed air temp– As the outside air allows, the outdoor air damper opens more
F h i / li h f i i i d – Free heating/cooling occurs when occupant comfort is maintained without using mechanical heating or cooling
E c o n o m iz e rS w itc h P o in t
o r A ir D am
p e r
He a tin g -C
o il V a ling -C
o il V a lv
e
1 0 0
pen
Ou td
o o r
V a lv e Co o li
O u ts id e A ir T e m p e ra tu re ( ºF )
M e c h a n ic a l H e a t in g F re e C o o lin g M e c h a n ic a l C o o lin g
5 0 7 0
0
6 5
M A M
% O
p
Section V - 36
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DDEMANDEMAND CCONTROLONTROL VVENTILATIONENTILATION
How It WorksHow It Works DCV provides just the right amount of outside needed by
occupantsM d l t til ti t i t t f / Modulates ventilation to main target cfm/person ventilation based on actual occupancy Less than 700 ppm above outside CO2 concentration
1 0 0 %
8 0 %
6 0 %
4 0 %nt B
uild
ing
Occ
up
ancy
or
t T
ota
l Ve
ntila
tion
Ca
pac
ity
2 0 %Pe
rce
Pe
rcen
t
B u ild in g O ccu p a n cy /D e m a n dV e n tila t io n C o n tro l
E n e rg y S a v in g s w ithD e m a n d C o n tro lle d V e n tila t io n
O cc u p a n cy P e r io dE n e rg y C o s t w ithD e m a n d C o n tro lle d V e n tila t io n
4 :0 0 6 :0 0 8 :0 0 1 0 :0 0 1 2 :0 0 1 4 :0 0 1 6 :0 0 1 8 :0 0 2 0 :0 0 2 2 :0 0 2 4 :0 0
Section V - 37
HHOTOT WWATERATER RRESETESET -- HHOWOW IITT WWORKSORKS
Hot water boilers are very efficient at partial load Distribution losses are less when temperature is reduced Hot water reset conserves energy by reducing the boiler’s
i operating temperature Hot water reset reduces thermal shock because it does not
involve drastic temperature fluctuations To minimize flue gas corrosion, do not reset lower than 60 ºC
Section V - 38
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HHOTOT WWATERATER RRESETESETProof of PerformanceProof of Performance
Maintaining 180ºF (82 ºC)water temperature forces the heating valves to cycle open and closed
180
130
80
70
60
160
150
140
170
180Hot Water Supply (ºF)
Valve Position (% open)
50
40
30
20
10
0
7:0
0
8:0
0
9:0
0
10:
00
11:
00
12:
00
13
:00
14:
00
15:
00
16:
00
17:
00
18
:00
19
:00
Outside Air Temp (ºF)
Section V - 39
HHOTOT WWATERATER RRESETESET
Proof of PerformanceProof of Performance Resetting the hot water temperature allows heating
valves to operate in more efficient mid-actuation positions180
130
80
70
60
160
150
140
170
Valve Position (% open)
Hot Water Supply (ºF)
Theoretical Potential Savings
50
40
30
20
10
0
7:00
8:00
9:00
10:
00
11:
00
12:
00
13:0
0
14:
00
15:
00
16:
00
17:
00
18:0
0
19:0
0
Outside Air Temp (ºF)
Section V - 40
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RREVIEWEVIEW::
BASBASBASBAS
Section V - 41
RREVIEWEVIEW: BAS/EMS: BAS/EMS
1. Distinguish between analog and digital controlcontrol.
2. Devices using 4-20 mA current loops are using digital data transmission.(A) True (B) False
Section V - 42
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3. A facility is heated by fan coil units using hot water pumped from a central boiler system List some EMS controls that could system. List some EMS controls that could reduce the facility energy costs.
4. List some maintenance aids that could be provided by an EMS.
Section V - 43
5. An optimum start device is a control function that:(A) Shuts off the outside ventilation air during start up of the building.
(B) Shuts off equipment for duty cycling purpose.
(C) Senses outdoor and indoor temperatures to determine the minimum time needed to heat up or cool down a building.
(D) Compares the enthalpy of outdoor and return air and determines the optimum mix of the two streams.
Section V - 44
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Control BasicsControl BasicsControl Functions & TerminologyControl Functions & Terminology
Overall RecapOverall Recap
BAS/EMS BasicsBAS/EMS BasicsBAS/EMS Functions & ProgramsBAS/EMS Functions & Programs
Section V - 45
APPENDIX
Section V - 46
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CCONTROLONTROL TTERMINOLOGYERMINOLOGY Set PointSet Point – The value of the controlled variable
that is to be maintained. Control PointControl Point - The actual value of the controlled
variable (temperature, pressure, flow, etc,).( p , p , f , ,) OffsetOffset - The difference between the set point and
the control point or the actual value of the controlled variable. (This is sometimes called drift, deviation, or control point shift.)
Direct Acting ControllerDirect Acting Controller – A controller for which an increase in the level of the sensor signal (temperature, pressure, etc,) results in an increase in the level of the controller output.p
Modulating ControllerModulating Controller – A type of controller for which the output can vary infinitely over the range of the controller.
Section V - 47
DifferentialDifferential – For a two-position controller it is the difference between the setting at which the controller operates at one position and the setting at which it changes to the other position. (All two-position controller need a differential to prevent “hunting,”
id li F h h diff i l i or rapid cycling. For a thermostat, the differential is expressed in degrees of temperature.)
DeadDead--BandBand – The range over which the output of the controller remains constant as the input varies, with the output changing only in response to an input outside the differential range.
Throttling RangeThrottling Range – The amount of change in the t ll d i bl i d t th t t f controlled variable required to run the actuator of
the controlled device from one end of its stroke to the other end. (If the actual value of the controlled variable lies within the throttling range of the controller, it is said to be in control. When it exceeds the throttling range it is said to be out of control.)
Section V - 48
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GainGain – The ratio of the output of the controller to the input. In a pneumatic temperature controller, for example, the gain would be expressed as:
gain = Controller Output (kPa)
Throttling Range (degrees)
Linear Percentage ValveLinear Percentage Valve – A valve with a plug shaped so that the flow varies directly with the lift.
Equal Percentage ValveEqual Percentage Valve – A valve with a plug h d th fl i th t f th shaped so the flow varies as the square root of the
lift. Flow (LPS) = Cv x √∆P
Section V - 49
WWATERATER FFLOWLOW TTHROUGHHROUGH VVALVESALVES
Section V - 50
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OOTHERTHER EMS PEMS PROGRAMSROGRAMS
1.1. Scheduled Start/StopScheduled Start/Stop – Starting and stopping equipment based upon the time of day, and the day of the weekand the day of the week.
2.2. Duty CyclingDuty Cycling – Shutting down equipment for predetermined short periods of time during normal operating hours.
3.3. Demand LimitingDemand Limiting – Temporarily shedding electrical loads to prevent exceeding a peak value.
4.4. Unoccupied SetbackUnoccupied Setback – Lowering the space pp g pheating setpoint or raising the space cooling setpoint during unoccupied hours.
Section V - 51
5.5. Warm Up/Cool Down Ventilation & Warm Up/Cool Down Ventilation & RecirculationRecirculation – Controls operation of the OA dampers when the introduction of OA would impose an additional thermal load during warm-up or cool-down cycles prior to occupancy of a building.
6.6. Hot Deck/Cold Deck Temperature ResetHot Deck/Cold Deck Temperature Reset -S l h / i h h h i d
ppSelects the zone/area with the greater heating and cooling requirements, and establishes the minimum hot and cold deck temperature differential which will meet the requirements.
7.7. Steam Boiler OptimizationSteam Boiler Optimization – Implemented in heating plants with multiple boilers. Boiler plant optimization is accomplishes through the selection of the most efficient boiler to satisfy the space temperature requirements during the building occupied period. R h C il/RR h C il/R8.8. Reheat Coil/ResetReheat Coil/Reset – Selects the zone/area with the greatest need for reheat, and establishes the minimum temperature of the heating hot water so that it is just hot enough to meet the reheat needs for that time period.
Section V - 52
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9.9. Chiller &/or Boiler OptimizationChiller &/or Boiler Optimization – For facilities with multiple chillers &/or boilers, the most efficient chiller(s) &/or boiler(s) are selected to meet the existing load with minimum demand and or energy.
10.10. Chiller Demand LimitingChiller Demand Limiting – The chiller electrical 10.10. Chiller Demand LimitingChiller Demand Limiting The chiller electrical load is reduced at certain times to meet a maximum pre-specified chiller kW load.
11.11. Lighting ControlLighting Control – Turns lighting off and on according to a pre-set time schedule.
12.12. Remote Boiler Monitoring and SupervisionRemote Boiler Monitoring and Supervision –Uses sensors at the boiler to provide inputs to the EMCS for automatic central reporting of alarms, critical p g ,operating parameters, and remote shutdown of boilers.
13.13. Maintenance ManagementMaintenance Management – Provides a maintenance schedule for utility plants, mechanical and electrical equipment based on run time, calendar time, or physical parameters.
Section V - 53
END OF SECTION V
Section V - 54
