Fancoils Engineering Guide

7/29/2019 Fancoils Engineering Guide

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Engineering GuideFan & Blower Coils

S E C T I O N F 1


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Product Fundamentals

Fan Coils and Blower Coils

Engineering Guide

Fan coils are a type o air handling unitdesigned to supply conditioned air to aroom or zone. The basic components thatmake up a an coil unit are a fnned-tubeheat exchanger, an section and flter. Thean produces orced convection across theheat exchanger, which circulates either hotor cold water to provide conditioned air tothe space. Individual zone thermostats arecoupled to the an coil’s an speed controllerand hydronic controls to maintain roomtemperature. A well-designed an coilunit will have low air and water pressuredrops across the coil to reduce an andpump power requirements as well as anefcient an and motor assembly or quiet

operation. Also, any an coil unit equippedwith a cooling coil should have a drain paninstalled to capture condensate, regardlesso whether or not the entering air is pre-conditioned. Fan coils are located in ornear the space to be conditioned or reedelivery o air into the zone or with minimalduct work. Units generally operate with ablow-through arrangement where the coil isdownstream o the an. Most an coil unitsare supplied with a direct drive an/motorassembly.

Most manuacturers certiy their an coilunits’ cooling perormance to the Air-Conditioning, Heating, and RerigerationInstitute standard AHRI Standard 440-2008: Perormance Ratings or Room Fan

Coils. The purpose o the standard is toprovide classifcations, test requirements,and minimum data requirements or thepublished ratings o an coil units deliveringup to 1500 cm.

Fan coils can be used in decentralized HVACsystems or in conjunction with a centralair handling unit. The major advantageso using an coil units are that they allowor local control o individual zones andreduce the overall ootprint o the systemby replacing ductwork with water pipingin a large portion o the system. They alsoreduce the amount o cross-contaminationbetween zones and allow or unused areasto be shut down. To receive ventilation air,an coils can either be ducted to a centralair handler or to a mixing plenum. Whenattached to a mixing plenum, care mustbe taken as an coils do not typically haveprovisions or controlling the amount o outdoor air admitted, and the coil must be

protected rom reezing in cold climates.

Fan Coil Components

• Access Panel – Removable sheet metal section allows access to internal mechanical

and electrical components.

• Belt Drive– The motor turns the blower by a belt connected to pulleys on each shatend. Each motor revolution will usually not be equal to one blower revolution.

• Blower/Fan – Multi-bladed, driven rotor enclosed so that air rom an inlet is

compressed to a higher discharge pressure.

• Casing – Structural sheet metal box or shell to which all components are secured.

• Coil – A heat exchanger in which liquid is circulated to provide heating or cooling to

the air which passes through the heat sink fns.

• Control Enclosure – Sheet metal shroud which houses the electrical connections,

speed controller and transormer. The enclosure cover prevents accidental electrical

shock as well as protects the contents rom the environment.

• Direct Drive – The motor shat is directly secured to the blower shat. Each motor

revolution is equal to one blower revolution.

• Discharge Collar – Rectangular ftting attached to the unit outlet allowing or quick

attachment o downstream ductwork.

• Drain Pan – Pan located under the cooling coil to catch condensate ormed during

cooling.

• Filter Rack – Tray in which a flter can be pulled out or maintenance or replacement.

• Liner – Internal blanket adhered to the casing that is used to reduce the radiated and/

or discharge sound levels. Materials used vary based on application and perormance

required.

• Motor – Electrical component o an air movement device that provides work to turn

the blade assembly.

DischargeOpening Coils

Discharge Panel

Fan AssemblyCoil Connections

Filter Rack

Drain Pan

Figure 1: View o Fan Coil Unit

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© Copyright Price Industries Limited 2011. All Metric dimensions ( ) are soft conversion .Imperial dimensions are converted to metric and rounded to the nearest millimetre. F1-3


Fan Coils and Blower CoilsEngineering Guide

Fan Coils with Dedicated Outdoor Air Systems (DOAS)

Oten an coil units are applied in adedicated outdoor air system (DOAS). In thisconfguration the air handler is selected todehumidiy and condition the outdoor airas well as to handle the space latent load.The an coil unit provides sensible coolingor heating at the zone (Figure 2). Thisconfguration has several advantages overa conventional VAV system. Decoupling thesensible and latent loads ensures properhumidity control at each zone. Additionally,the exact outdoor air requirements to eachzone can be maintained, eliminating over-ventilation and ensuring compliance withASHRAE Standard 62-2001—Ventilation orAcceptable Indoor Air Quality (IAQ). Energy

savings can be realized due to reducedterminal reheat and reduced outdoor air.Additionally, the DOAS system can beturned o during unoccupied hours with thean coils maintaining local zone temperaturecontrol.

In Figure 2 the outdoor air is delivereddirectly to the space through a separatediuser, independent o the an coil unit.This allows the an coil unit to be turnedo or run at low speed during part loadconditions. Note that i a low supply airtemperature (less than 55 °F) is requiredor dehumidiication, a high inductiondiuser should be selected to preventdrats. Another option is to duct the

outdoor air into the an coil unit (Figure 3).In this case the an coil must run during partload, however ductwork is minimized.

Figure 2: Outdoor air ducted through separate diusers

Figure 3: Outdoor air ducted into an coil unit

Supply Air Outdoor

Air

Return Air Relief Air

Zone 1

CLASSROOM

Zone 2

CLASSROOM

AHU

F a n

C o i l

U n i t

F a n

C o i l

U n i t

T T

Outdoor

Air

Relief Air

Zone 1

CLASSROOM

Zone 2

CLASSROOM

AHU

F a n

C o i l

U n i t

F a n

C o i l

U n i t

T T






Figure 7: Horizontal Exposed Fan Coil

Figure 6: Horizontal Concealed Fan Coil

Low Pressure Fan Coils

Low pressure an coils are generallylocated in or adjacent to the space to beconditioned. They are usually selected orree delivery o air into the zone or withminimal ductwork having a static resistanceo less than 0.25 in. w.g. A well-designedunit should be equipped with an easilyremovable lter, drain pan and an/motorassembly to reduce maintenance costsand improve indoor air quality. Theyare normally oered in nominal air fowsizes up to 1200 cm and use multispeed,high-eciency motors. Units commonlyhave single point power connections andthree position (plus shutdown) an speedcontrollers. Units are available in vertical orhorizontal congurations or exposed andconcealed applications as shown in Figure4 and Figure 5.

Concealed Units

Concealed units can be urred into a wall orinstalled in a ceiling plenum and then aretypically ducted to a single discharge grilleor diuser as shown in Figure 6.

Exposed Units

Exposed units are generally installed ina visible location and thereore have anattractive painted nish and return andsupply air grilles as shown Figure 7. Unitsuse ully insulated casings to reduce the

amount o noise delivered to the occupiedspace, and the ootprint is designed to besmall to minimize the amount o occupiedspace they require.

Typical Applications

Low pressure an coils are ideally suitedor applications where individual zonetemperature control is required. Thismakes them an ideal candidate or hotels,apartment buildings and oce buildings(ASHRAE, 2008a). In many cases verticalunits are installed so that the supply air‘washes’ the window and helps lower thethermal impact o the glass. Fan coils can beused in health care acilities, but care shouldbe taken because o their low-eciency

lters and because they are designed mostlyor re-circulated air which is not permittedin certain types o spaces.


Fan Coil Unit Types

Figure 4: Vertical Updrat Fan CoilArrangement

Figure 5: Horizontal Fan CoilArrangement

Filter

Fan

Coils

Discharge Air Opening

Return Air Opening

Cross Section View

FilterDuct Ceiling FanCoils

Cross Section View







Figure 8: Classroom installation


Fan Coil Unit Types

High Performance Fan Coils

High perormance an coils are designedor higher air volumes, higher staticpressures, low noise levels and better roomtemperature control. To achieve the lowersound levels the high perormance ancoils typically utilize larger an blowers toreduce outlet velocity and ully enclose thean/motor assembly in an insulated casing.They are normally oered in a horizontalconcealed conguration as shown in Figure9 and are ducted to one or more supplyair grilles. Because o their higher staticpressure capabilities, high perormance ancoils can be equipped with higher eciencylters and more rows o heating-cooling

coils. A well-designed unit should still becapable o quietly and eciently deliveringmaximum fow when ully equipped withcoils and lter at 0.5 in. w.g. o external staticresistance. Another benet o the higherstatic pressure capability is that the unitcan accommodate longer discharge ductruns with multiple air outlets. This allowsthe an coil to be mounted arther rom theoccupied space reducing acoustic concerns.As an example or a classroom application,the an coil unit can be located abovethe hallway where noise levels are lesscritical. Additionally, the longer length o downstream ductwork can be acousticallylined or urther noise reduction. Due to theirhigher air fow capacity and static pressure

capability, larger rooms or spaces can besupplied with high perormance an coilunits.

To achieve the higher lows and staticpressures and still maintain eciency, highperormance an coils are oten equippedwith electronically commutated motors(ECM). ECMs also allow or ull rangedigital speed controllers and constant fowprogramming. Full range speed controlallows the an speed to be optimized atthe setting which meets the room loadand acoustic design goals. Constant fowprogramming ensures the an fow will bemaintained even as the lter resistanceincreases due to dust buildup.

When coupled with electronic or DDCcontrols ECMs can also be operated toprovide variable volume o both cooling andheating an fows, contributing to urtherenergy savings and enhanced comort. Seepage 608 or details.

High perormance an coils can beperormance certiied up to 1500 cmunder the AHRI Standard 440-2008. Unitsoperating beyond the scope o this standardshould still be tested and rated underthe same conditions to ensure reliableperormance in the eld.


High perormance an coils are an excellentchoice or applications where a high level o

individual zone temperature control and lownoise is required. This makes them an idealcandidate or schools, hotels, apartmentsand oce buildings. Higher air volume andstatic pressure capability also make themideal or larger spaces and applicationsrequiring longer duct runs and multiple airoutlets such as labs, meeting rooms, halls,lecture theaters, etc.

The high cooling capacity available withhigh perormance an coils meets the needso high load spaces such as labs, perimete

zones with high solar loads, and highoccupancy spaces. High perormance ancoils are also well-suited or hospitals andlaboratories because o their constant fowprogrammability and their ability to usehigher eciency lters. The high eciencyand VAV capability o ECM technologycoupled with the energy ecient benetso hydronic cooling or heating and theIAQ benets o a DOAS system lends welto LEED certication and green buildingdesign.

Figure 9: Horizontal High Perormance Fan Coils

CLASSROOM

Supply

Return

Duct

High PerformanceFan Coil Unit

Corridor






Blower Coil Unit Types

Blower Coils Overview

Blower coils are a type o air handling unitthat can be used to provide one or multiplezones with conditioned air. They consist o a nned-tube heat exchanger, an, and lterin a draw-through conguration as shownin Figure 10. The heat exchanger usuallyconsists o a water coil or hot or chilledwater, but steam coils and direct expansioncoils may also be used. Regardless o thetype o coil, all the conditioned fuid mustbe piped to the unit rom another pieceo localized equipment such as a boiler orchiller. Unlike an coil units where the an isdirectly coupled to the motor, blower coilstypically use a belt drive system to transmit

power rom the motor to the an.This allowsthe an to run at whatever speed is requiredsimply by changing the pulley set in the unit.A well-designed blower coil unit should becompact, have low air and water pressuredrops across the coil to reduce an andpump power requirements, be an ecientblower and belt drive system, and providegood access to all o the unit’s componentsor regular maintenance. It should also havea ully insulated casing to reduce heat lossto/rom the conditioned air and a tight lterrack to eliminate lter bypass.

Blower coils are a compact solution to avariety o ducted applications that requirefexibility between the traditional an coilunit and a central station air handling unit.

They are generally capable o handling atleast 1 in. w.g. o external static resistanceand can be equipped with more rows o coils and higher eciency lters than ancoils. This allows them to be used as acentral station air handler or constantvolume systems or to be coupled with avariable requency drive and used or avariable air volume (VAV) system. Theirsmall size also allows them to be used as aconstant volume an coil to condition onlyone room i required. Because o the largefow and static pressure ranges, blowercoils are available with single and threephase motors ranging rom 1/3 hp up to10 hp. They are typically located outsidethe conditioned space in an area such as

a service room or basement, but they canbe installed in the area i conditions permit.Blower coils come in vertical and horizontalcongurations as shown in Figures 11 and12, depending on i they are to be installedon the foor or hung rom the ceiling.


Figure 10: Draw -Through Unit

Figure 11: Floor-Mounted Vertical Unit

Figure 12: Ceiling-Mounted Horizontal Unit

Cross Section View

OutdoorAir

Supply Air

Return AirFilter Ceiling DuctFanCoils







Discharge Opening

Heavy GaugeInsulated Casing

Access PanelsBelt DriveFan Assembly

Coil & DrainConnections

Insulation

Filter RackCoils

Blower Coil Unit Types

Access Panel

Removable sheet metal section allows

access to internal mechanical and electricalcomponents.

Belt Drive

The motor turns the blower by a beltconnected to pulleys on each shat end.Each motor revolution will usually not beequal to one blower revolution.

Blower/Fan

Multi-bladed, driven rotor enclosed so thatair rom an inlet is compressed to a higherdischarge pressure.

Casing

Structural sheet metal box or shell to whichall components are secured.

CoilA heat exchanger in which liquid is circulatedto provide heating or cooling to the air whichpasses through the sink ns.

Control Enclosure

Sheet metal shroud in which houses theelectrical connections, speed controller, andtransormer. The enclosure cover preventsaccidental electrical shock as well as protectsthe contents rom the environment.

Direct Drive

The motor shat is directly secured to the

blower shat. Each motor revolution is equato one blower revolution.

Discharge Collar

Rectangular tting attached to the unit outleallowing or quick attachment o downstreamductwork.

Filter Rack

Tray in which a lter can be pulled out ormaintenance or replacement.

Liner

Internal blanket adhered to the casing that isused to reduce the radiated and/or dischargesound levels. Materials used vary based onapplication and perormance required.

MotorElectrical component o an air movemendevice that provides work to turn the bladeassembly.

While blower coils may be rated or anominal fow, they are not restricted bya limited number o incremental motorspeeds. They are capable o operating atany fow and static pressure within theiroperating range. This ability, coupled witha large number o coil combinations andaccessories such as electric reheat, mixingplenums and UV lights, means that blowercoils, like other air handlers, can be morecomplicated to speciy or order.

The design engineer needs to speciy manyparameters such as supply air temperatureand volume, outside air requirements, fuidtemperatures and fow rates, external staticresistances and more, beore an equipment

supplier can provide the proper blower coilunit.

Manuacturers can certiy their blower coilunits an perormance to the AHRI Standard430-2009: Perormance Rating o CentralStation Air-Handling Units. The purpose o the standard is to provide classications,test requirements and minimum datarequirements or the published ratings o central station air-handling units. Watercoils used in blower coil units should alsobe AHRI certied to AHRI 410-2001: ForcedCirculation Air-Cooling and Air-HeatingCoils. By using equipment that is certiedto these standards, the design engineer canbe condent that units will unction properlyunder the conditions that are specied.


Blower coils are an excellent choice orapplications where high cooling capacitiesor external static pressures cannot be metwith standard or high perormance directdrive an coil units. This makes them an idealcandidate or schools, hotels, apartmentsand oce buildings. Also, with their abilityto operate with up to 100% outdoor air and avariety o options such as mixing boxes, UVlights and solid metal liner, blower coils arealso well-suited or hospital and laboratoryapplication.

Fan coil system and zone piping can becongured in several ways to meet therequirements and priorities o the systemdesigner. System eciency, fexibility andrst cost are the primary drivers o thesystem piping design. The entire system(an coils, piping, pumping, chillers andboilers) needs to be considered to conrmthat appropriate compromises are made tomeet the system goals.


Figure 13: Fan Coil/ Blower Coil Product Components (Exploded View)






Series and Parallel Piping

The piping system can be designed with twobasic piping concepts ‒ series or parallelpiping. In a series type system, a single pipeloop is utilized to supply water in a loop. Theindividual an coils take water rom this loopand discharge back to the loop. As more ancoils take rom and return water to the seriesloop, the temperature in the loop is changed.It progressively increases in a chilled waterloop and progressively decreases in a hotwater loop. The an coils at the end o theloop see water temperatures that provideless potential capacity than the an coil atthe beginning o the loop. These an coils atthe end o the loop will require larger coils

to provide similar capacity. The benet o this type o system is the elimination o thereturn piping and the cost associated withit, but must be weighed against the cost o larger coils in the an coils that are later inthe loop.

In a parallel system, there is a supply pipeand a return pipe. Each an coil unit receiveswater at the same temperature giving eachthe same capacity opportunity. Coils canbe selected with similar temperaturecharacteristics providing or more consistentsmaller coils.

Load Pumps

In a series piping system, load pumps isa way to pull water rom the water fow in

the series piping and supply it to the coilin the an coil unit. As capacity is requiredto meet the load, the pump pulls waterrom the loop to provide the heating orcooling capacity required. This type o design provides simple design and controlo the loop and the loads. The loop pipingexperiences constant fow and pressure.The load pump and piping at each an coilunit is designed to only meet the pressureand fow requirements o the loop. Eachoperates and is controlled independently o the other. In some cases, control valves areprovided in the loop piping to conrm thatthere is no fow in the loop system when theloop system is shut down. See Figure 14.

Fan Coil Piping


Figure 14: Piping Systems

Series System With Load Pumps

Fan Coil Unit

Fan Coil Unit

Fan Coil Unit

Paralled System

Fan Coil Unit

Fan Coil Unit

Fan Coil Unit







Direct & Reverse Return

An important consideration in designingthe system is ensuring that each an coilcan receive the desired chilled water or hotwater fow rates during system operation.Two types o systems can be utilized—direct return or reverse return. In a directreturn system, as shown below, the pipingis run in the shortest method possible andbalancing valves are used to manipulate thepressure drop through each piping zone toensure each an coil receives the requiredwater fow. This requires the system tobe ‘balanced’. These valves must be setthrough an iterative process to veriy thefow through each coil. As each valve is

changed the rest o the system is aectedand they must be adjusted until the systemachieves steady state fow at each an coil.See Figure 15.

In a reverse return system, the pipe lengththrough each piping zone is laid out to beequal. This ensures that the pressure dropthrough the piping system is equal or eachan coil unit. This works well i the pressuredrop through each coil and piping loop isvery similar. This can be accomplished byusing the same pressure drop criteria or thecoils, and the same pressure drop criteriaper oot o pipe. While more piping needsto be installed, the “balancing” requiremento the system is eliminated. See Figure 16.

2 Way and 3 Way ValvesThe an coil zone piping system can bedesigned or constant volume or variablevolume water fow. A constant volumesystem would require 3 way type controlvalves to modulate the water fow throughthe coil or around the coil to provide aconstant water low through the zonepiping. A balancing valve is installed in thebypass to maintain constant pressure dropas the water fow is modulated around thewater coil. This type o constant fow systemwith 3 way control valves is very simplerom a control and layout perspective, butcontinues to run the pump at ull powerduring part-load conditions.

For a variable fow, 2 way control valves arerequired. In this type o system the pressurein the supply piping header is measuredand the pump output is varied to controlthe constant pressure in the system. As 2way valves are closed the system “rides”the pump curve. At lower fow the pumpincreases the pressure in the system. Thepressure control then slows the pumpdown to provide a lower fow at constantsystem pressure. As fow is lowered thepump requires signicantly less power. Apump with a curve that has good predictiveperormance throughout the anticipated

Fan Coil Piping


water fow rate should be selected. Pumpswith very fat curves should be avoidedas small changes in pressure would leadto large changes in fow, creating systemcontrol issues.

Figure 17: Constant Flow

Figure 16: Reverse Return

Figure 15: Direct Return

Figure 18: Variable Flow

Fan Coil Unit

Fan Coil Unit

Fan Coil Unit

Fan Coil Unit

Fan Coil Unit

Fan Coil Unit






Figure 20: Common Coil 4 Pipe System

Capacity Control

In each o the above system and controldesigns, capacity control can be on-o ormodulation. On-o control would provideno water fow when the control system issatised. Oten in a an coil system the anwould also be turned o during this satisedmode. When the control system calls orcapacity, the water fow would be providedat ull design fow and the an would beenergized to ull air fow.

These systems can also utilize modulatingcontrol. Water fow would be varied toprovide the desired amount. In systemsdesigned to experience varying enteringconditions, the fow can be varied to maintaina constant leaving air temperature basedon a constant air volume. The water fowcan also be varied to provide less capacityby changing the leaving air temperaturebased on a constant fow. Also, variablewater fow and air fow can be provided. Theair fow is decreased as the load decreasesand the water fow is regulated to maintaina constant leaving air temperature. This isan uncommon control strategy or a ancoil system, but would provide enhanceddehumidication perormance at low loadconditions.

Separate or Common Cooling andHeating Coils

Fan coil units are readily available with

either a single coil or with both a heating andcooling coils. When heating and cooling isrequired, they are most oten provided withboth heating and cooling coils. In this typeo system, each coil is piped and controlledindependently. Generally there is sometype o dead band in the control systemto eliminate the possibility o heating andcooling simultaneously.

In a single coil system, where it operates ineither heating or cooling, the system canbe a 2 pipe or 4 pipe system. In a 2 pipesystem, either hot water or chilled water issupplied to the entire system depending onthe season. The an coils are controlled tomaintain the required heating or coolingleaving air condition. In a 4 pipe system,each an coil can be heating or cooling.This allows some parts o the system toprovide cooling while other parts provideheating. This is oten required in buildingswith interior zones that require cooling allyear in all seasons. In this case 3 way valvescan be used to select either heating supplyand return or cooling supply and return.This type o system provides the greatestfexibility while lowering the rst cost o thean coil units.

Fan Coil Piping


Figure 19: Separate Coils 4 Pipe System

Heating Coil

Fan Coil Unit

Cooling Coil

Fan Coil Unit

Common Coil







Fan Coil Controls

Generally an coils are applied to controlthe space temperature o a room or zone.A typical control system would consist o athermostat, multi speed an, a heating coilwith control valve and/or a cooling coil withcontrol valve. Some systems may includecooling only and some heating only. Severallevels o control sophistication are availabledepending on the accuracy o temperaturecontrol and energy eciency required.

Basic Electric Control

The simplest and most basic controlsystem would be manual adjustment o the an fow and manual activation o theheating or cooling coil. In this case thethermostat has a temperature adjustmentdial, a manual switch or an operation atone o three speeds or o, and a manualswitch or selecting either cooling or heatingmode. Figure 21 illustrates a typicalmanually switched thermostat. Generallythe thermostats are powered by line voltageand directly connected to the an and valveactuator (Figure 22).

Figure 23 illustrates the control sequenceor a manually controlled heat-coolchangeover an coil control system. Duringcooling mode the cooling coil will be turnedon i the room temperature rises above set-point. During heating mode the heating coilwill be turned on i the room temperaturedrops below set-point. The operation o

the cooling or heating coil is ull on or o.Either a 2 pipe or 4 pipe water supply canbe accommodated.

An enhancement to the above sequence isautomatic control o heating or cooling bythe thermostat. I a 2 pipe system is used awater temperature sensor is adhered to thesupply water pipe to allow the thermostat todetect i hot or cold water is available andautomatically switched between heatingor cooling mode. With a 4 pipe systemthe thermostat will automatically activatecooling mode when the room temperatureis above the thermostat set-point andheating mode when the room temperatureis below set-point. A urther enhancementto the same sequence is automatic control

o the an. The thermostat energizes the anat the selected speed when there is a callor heating or cooling. The level o controlenhancement will be determined by thethermostat model selected.


Figure 21: Manually Switched Fan Coil Thermostat

Figure 22: Typical Wiring Diagram - Basic Electric

Figure 23: Sequence o operation or manually selected an speed and manualheat-cool changeover

F a n C o i l

T e r mi n a l B l o c k

L

SR Jumpers

SR1 SR2

G1 G2 G3 W/YAutomaticTemperatureControl Valve

Neutral

Low

Med

High

Line 1

O p e r a t i n g V

o l t a g e

Thermostat Terminals

Factory Electrical Wiring

Field Electrical Wiring

F a n S p e e d I ( L o w )

F a n S p e e d I I ( M e d )

F a n S p e e d I I I

( H i g h )

C o n t r o l O u t p u t

Min. Air Flow

Dead Band3 Speed Fan Flow

High High

Med Med

Low Low

0.9oF 0.9oF

V a l v e

S i g n a l

Tset-point

Max. Air Flow

On

Off

Heating ON Cooling ON

Cool WarmRoom Condition






Fan Coil Controls

Analog Electronic Control

Analog electronic control systemsoffer several advantages over the basicelectric package, including more preciseproportional integral (PI) control of roomtemperature, optional modulating control of the cooling and heating coil, and an optionalLCD display for user-friendly monitoringand selection of control parameters. Figure24 illustrates a typical analog thermostatwith LCD display. Generally the thermostatsare powered by 24 VAC from a controltransformer (Figure 25). Figure 26 illustratesthe control sequence for an automaticheat-cool changeover fan coil system withmodulating control of heating and cooling.


Figure 24: Analog Thermostat with LCD display

Figure 25: Typical Wiring Diagram - Analog Electronic

Figure 26: Sequence of operation for automatic heat-cool changeover andmodulating control of heating and cooling

Changeover SensorField Installed

+24V Hot 1+24V Hot 1

+24V Open

+24V Closed

-24V Com 2

- 2 4 V C o m

-24V Com 2

Air Temperature Sensor(Not Included)

1 2 3 4 6 7 8 9 10 11 12 D1 GND

N e u t r a l

N e u t r a l

O p a r a t i n g V o l t a g e 2 4 V A C

3 P o s i t i o n V a l v e ,

O p e n S i g n a l

3 P o s i t i o n V a l v e ,

C l o s e S i g n a l

C h a n g e o v e r S e n s o r I n p u t

M e a s u r i n g N e u t r a l

R e t u r n A i r T e m p I n p u t

F a n S p e e d I I I ( H i g h )

F a n S p e e d I I ( M e d i u m )

F a n S p e e d I ( L o w )

P o t e n t i a l - F r e e O p e r a t i n g

M o d e C h a n g e o v e r S w i t c h I n p u t

AutomaticTemperatureControl Valve

Factory Electrical Wiring

Field Electrical Wiring Thermostat Terminals

Min. Air Flow

3 Speed Fan Flow

High High

Med Med

Low Low

3.6oF

V a l v e

S i g n a l

Tset-point

Max. Air Flow

Open

Closed

Heating ON Cooling ON

1.8oF


GREEN TIPDuring occupied hours the fan shouldbe operated to maintain ventilation airto the space.

GREEN TIPPI control and modulating water valvesminimize room temperature over-shoot providing energy savings.







Fan Coil Controls

GREEN TIPReducing the supply air temperatureduring overhead heating will limitstratication and improve indoor airquality.

GREEN TIPECMs consume considerably lesspower at part load operation thanstandard PSC motors, providingurther energy savings.

Digital Programmable Control

Similar to the analog control system, thedigital thermostat includes proportionalintegral (PI) control o room temperature,modulating control o the cooling andheating coil, and an optional LCD display.However the addition o an on-boardmicroprocessor provides enhancedunctionality and lexibility. Digitalthermostats typically are shipped pre-programmed or the desired sequence o operation but can be easily reconguredin the ield i required. Figure 27illustrates ield coniguration o theprogrammable thermostat with a laptopPC and interace module.

More custom or specialized controlsequences can also be accommodated.One example is control o discharge airtemperature to a selectable set-point withthe addition o a discharge temperaturesensor. During cooling a minimumdischarge air temperature may be desiredto maintain control o humidity. Duringheating a maximum air temperature maybe desired to prevent stratication in theroom i ceiling mounted outlets are utilized.Figure 28 illustrates the control sequenceor automatic heat-cool changeover andmodulating control o heating and cooling,with discharge air temperature control o the cooling fow.

I the an coil is supplied with an ECM thedigital thermostat can be programmed toprovide modulating control o the an fowduring both heating and cooling modes o operation. This enhanced unction providessuperior comort control, energy savings andimproved acoustics. Figure 29 illustrates thecontrol sequence or automatic heat-coolchangeover, modulating control o heatingand cooling with discharge air temperaturecontrol o the cooling and heating fow andvariable an speed.


Figure 27: Field Programmable Thermostat

Figure 28: Sequence o operation or automatic heat /cool changeover and modulatingcontrol o heating and cooling, with discharge air temperature control o the cooling fow.

Figure 29: Sequence o operation or automatic heat /cool changeover, modulatingcontrol o heating and cooling with discharge air temperature control o the coolingand heating fow and variable an speed.

Min. Air Flow

High High

Med Med

Low Low

2 oF

1oF 1oF

V a l v e

S i g n a l

Tset-point

Max. Air Flow

10 Volts

0 Volts

HeatingON

CoolingON

2 oF

Dead Band


Min. Air Flow ECM

V a l v e

S i g n a l

Tset-point

Max. Air Flow ECM

10 Volts

0 Volts

HeatingON

CoolingON

Dead Band


2 oF1oF 1oF

2 oF






Fan Coil Controls

Digital Control with Networking

Fan coils can be supplied with a networkeddigital control package which allowscommunication to and remote controlrom a central BAS system. Typically thedigital control package would includea room thermostat and a control boardwith programmable inputs and outputs(Figure 30), as well as network capabilityto communicate with a central BAS or otherront-end system.

The additional inputs and outputs on thecontroller allow advanced control sequencesutilizing occupancy or CO2 sensors, lightingcontrol or operation o other auxiliarydevices. Network communication providesall the room comort, energy savings, andmaintenance benets o a ull DDC system.

Wireless Thermostat

Digital programmable thermostats can besupplied in a wireless conguration. Thethermostat is battery powered and sendsa wireless signal to the digital controllermounted on the an coil which is equippedwith a wireless receiver. Each thermostatand controller are paired through a uniqueselectable address.The wireless thermostatis easier to install and can be mounted onalmost any surace in the room. All controlunctions and eatures o the networkeddigital programmable thermostat systemwould be available.

Application of Fan Coil and Blower Coil Units

While blower coils and an coils areundamentally very similar, deciding whichtype o unit to use and in what congurationis not always straightorward. Consultationsbetween the designer and owner maybe required to weigh the beneits o perormance, fexibility and maintainabilityversus cost.

CapacityBlower Coils are capable o higher air fowsand static pressures than Fan Coils. For thisreason, Fan coils are typically smaller andare used to condition the room in whichthey are located, whereas Blower Coilsare moderate-sized and can be ducted tocondition several rooms. This is not alwaysthe case though as High Perormance FanCoils have lled the gap between the twoproducts by oering capacities close tothose o blower coils while still retainingthe small size o a an coil unit.

Controls

Fan coils are typically controlled by eithera thermostat or an speed switch in theroom that they are conditioning (ASHRAE,2008a). This makes them well-suited orapplications where a high level o individualcontrol is desirable, such as hotel rooms, orwhere there are inrequent loads, such as a

meeting room. Blower coils on the otherhand are typically operated as constant airfow units. I required, they can be equippedwith variable requency drives or VAVcontrol, however the cost will be higher.High perormance an coils can be equippedwith ECMs programmed to deliver constantair fow within a range o static pressures.

Noise

Both an coils and blower coils generatea signicant amount o an noise so theirapplication and location needs to becareully considered. Fan coils tend tobe quieter so they can be located in theconditioned space as an exposed unit ordirectly adjacent to the space in a ceiling

plenum or wall cavity. Exposed units shouldbe ully lined with berglass insulation toreduce radiated noise.

Fan coils by design are intended to belocated in or directly adjacent to theoccupied space. They can be installed inwalls, ceiling plenums, closets, and manyother areas close to the room they serve.Noise is a large concern as there is otenlimited ability to provide sound attenuationtechniques in the building material betweenthe unit and the space or in the supply andreturn ductwork. The location o the ancoils needs to be reviewed to conrm thatthe sound level in the adjacent space isacceptable.


Figure 30: Fan Coil Controller

Figure 31: Wireless Thermostat

Digital Controller Reciever







Unit Type

Ofce Space,Educational Facilities

Hospitals,Clean Rooms,Laboratories

L a r g e

B u i l d i n g s

S m a l l

B u i l d i n g s

P a t i e n t

A r e a s

O p e r a t i n

g

A r e a s

L a b o r a t o

r y

S p a c e s


High Performance Fan Coils - -

Blower Coils

Application of Fan Coil and Blower Coil Units

Type Fan Cabinet cm Ext Static

Horizontal Direct Exposed / Concealed < 2,000 <0.5 in.

Horizontal-Hi press

Direct Exposed < 4,000 1.0 in.

Vertical Direct Exposed / Concealed < 2,000 0.5 in.

Hi-rise Direct Concealed < 2,000 0.5 in.

Ext Static is external static pressure, in. w.g.

Type Fan Cabinet cm Ext Static

Horizontal Belt Exposed < 8,000 1 in. to 3 in.

Vertical Belt Exposed < 8,000 1 in. to 3 in.

Ext Static is external static pressure, in. w.g.

Table 1: Fan Coil Congurations

Table 2: Blower Coil Congurations

Table 3: Application Guidelines

Locating the an coil unit in or over spaceswith higher sound criteria is oten used tominimize the occupant objections. Locatingthem above a bathroom ceiling would bean example o this technique. Selecting theunits at lower than the maximum air fowthe unit can produce is a method o loweringthe noise produced by the an coil unit.

Larger ans running at slower speeds otenprovide improved noise characteristics,but will require greater rst cost o theunit. Sound data rom the manuacturershould be reviewed with options to reducethe noise levels to achieve acceptable spacenoise design.

Blower coils can be equipped with integralsilencers to signiicantly reduce theirdischarge noise. They can then be locatedaway rom the noise sensitive space andducted to the room.

Contaminant Control

Most an coils and blower coils are equippedwith a lter, but the level o ltration variesgreatly. Low pressure an coils are typicallyonly equipped with MERV 3 lters becausethey are not capable o overcoming the largepressure drop caused by higher eciencypleated lters. High perormance an coilscan be equipped with medium eciencylters up to MERV 13. I a high degree o contaminant control is required, blowercoils can be equipped with high-eciency

lters (up to MERV 15) and UV lights. Blowercoils can also be equipped with HEPA ltersi special care is taken to seal the unit casingagainst inltration o non-ltered air.

Outdoor Air

Fan coils should not be used to conditionoutdoor air as they are not designed tohandle high levels o humidity. They do nottypically have deep enough coils to providethe level o dehumidiication required,and condensate carryover can occur inhigh humidity locations due to high acevelocities on coils caused by the typicalblow-through conguration. Blower coilson the other hand have the static pressurecapabilities required to use deep coils and

can be equipped with mixing boxes tocombine re-circulated air with outdoor air.One notable exception is that an coils arewell-suited or heating only applicationswhere there are high inltration rates o outdoor air such as using an exposedvertical an coil to heat a vestibule or lobby(ASHRAE, 2008a).


Unit Type

Noise SensitiveApplications

Other Facilities

B r o a d c a s t

S t u d i o s

T h e a t e r s

P u b l i c U s e

S h o p p i n g

C e n t e r s

H o t e l s ,

M u l t i

R e s i d e n t i a l


High Performance Fan Coils - - - -

Blower Coils - -

Often Used for this application Not Recommended for this application

- Sometimes used for this application (restrictions may apply)






References


AHRI (2001a). AHRI standard 260-2001: Sound ratings o ducted air moving and conditioning equipment.Arlington, VA: Air-Conditioning, Heating, and Refrigeration Institute.

AHRI (2001b). AHRI standard 410-2001: Forced circulation air-cooling and air- heating coils. Arlington, VA:Air-Conditioning, Heating, and Refrigeration Institute.

AHRI (2008a). AHRI standard 440-2008: Perormance rating o room an-coils. Arlington, VA: Air-Conditioning,Heating, and Refrigeration Institute.

AHRI (2008b). AHRI standard 885-2008: Procedure or estimating occupied space sound levels in the application o air terminals and air outlets. Arlington, VA: Air-Conditioning, Heating, and RefrigerationInstitute.

AHRI (2009). AHRI standard 430-2009: Perormance rating o central station air- handling units. Arlington, VA:Air-Conditioning, Heating, and Refrigeration Institute.

ASHRAE (2001). Standard 62-2001—Ventilation or acceptable indoor air quality. Atlanta, GA: American

Society of Heating, Refrigeration and Air-Conditioning Engineers.ASHRAE (2007a). ASHRAE handbook—HVAC applications. Atlanta, GA: American Society of Heating,

Refrigeration and Air-Conditioning Engineers.

ASHRAE (2007b). Standard 52.2-2007—Method o testing general ventilation air-cleaning devices or removal efciency by particle size. Atlanta, GA: American Society of Heating, Refrigeration and Air-ConditioningEngineers.

ASHRAE (2008a). ASHRAE handbook—HVAC systems and equipment (SI edition). Atlanta, GA: AmericanSociety of Heating, Refrigeration and Air-Conditioning Engineers.

ASHRAE (2008b). Standard 130-2008—Methods o testing air terminal units. Atlanta, GA: American Societyof Heating, Refrigeration and Air-Conditioning Engineers.

ASHRAE (2009). ASHRAE handbook—Fundamentals. Atlanta, GA: American Society for Heating, Refrigeratingand Air Conditioning Engineers, Inc.

Price Industries (2011). Price engineer's HVAC handbook—A comprehensive guide to HVAC undamentals.Winnipeg, MB: Price Industries Limited.



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Fancoils Engineering Guide

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