HVAC Guide Final Low

8/3/2019 HVAC Guide Final Low

1/46

BuildingTechnologiesProgram

hVacctg

fPexBipt

September 2011

at:

EricMakela,PNNL

JamesRussell,PECI

SarahFujita,PECI

CindyStrecker,PECI

PreparedbyPacicNorthwestNationalLaboratory

ortheU.S.DepartmentoEnergyBuildingTechnologiesProgram


2/46

2

ctt

itt 3

hw t u t g 4

c rqt cp ck 9

Perormance Path 10

Control Requirements or All Systems 11

Thermostatic Control o Heating and Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Supply Fan Motor Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Ventilation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Heat Pump Supplemental Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Prescriptive Requirements or Simple Systems 22

Economizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Hydronic Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Control Requirements or Complex Systems 26

Economizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Variable Air Volume (VAV) Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Humidity Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Hydronic Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Hydronic Heat Pump and Unitary Air Conditioning Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Fan Speed Control or Heat Rejection Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Multi-zone Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42


3/46

Introduction 3

itt

ThepurposeothisguideistoprovideanaidthatwillmakeiteasiertoapplytheHVACcontrolrequirements

oundinbuildingenergycodes.Thisguideaddressesrequirementsdenedbytheollowingcodesand

standards,whicharecommonbasesorthecodesthatareadoptedbystateandlocaljurisdictions:

TheInternationalEnergyConservationCode(IECC),versions2009and2012.

TheAmericanSocietyoHeatingandRerigerationEngineeringAssociation

(ASHRAE)Standard90.1,versions2007and2010.

EnsuringcompliancewithHVACcontrolrequirementsisadiculttask,ascontrolscanbediculttoidentiyon

plansorinthebuilding.Yetitisacrucialtask.HVACcontrolsareakeydriverobuildingperormanceandwithout

complianceandenorcementactivitiesthecoderequirementsmaybeignored,overlooked,ormisunderstood.

Does the control system _____________?WhenitcomestoveriyingtheproperimplementationocertainHVACcontrols,theressimplynoway

abuildinginspectorcandoitalone.Therearetoomanypossiblesystemcongurationstounderstand

andtoolittletime.Recognizingthislimitation,thisguideaimstoprovidecodeocialswiththe

backgroundrequiredtoaskmeaningulquestions.Forexample:

Doesthecontrolsystemincludeintegratedeconomizercontrol?

Doesthecontrolsystempreventsimultaneousheatingandcooling?

Doesthecontrolsystemresetthechilledwatersupplytemperaturebasedondemand?

Compliancecanthenbeachievedusingamixothesuggestedchecksinthisguide,goodquestions,

andrequestsortheengineerorbuildertoshowhowthesystemcomplies.


4/46

4 Introduction

hwtutg

Atabasiclevel,theHVACcontrolsrequiredbybuildingenergycodesareeasytounderstand.Theymake

surethatequipmentturnsonwhenitisneeded,owhenitisnt,andthatwhileoperatingitdoesntconsume

moreenergythanneededtomakepeoplecomortableinthebuilding.Inthisguide,wedescribethechecks

thatplansexaminersandbuildinginspectorscanmaketoensurethatthesebasiccontroleatureshavebeenproperlyincludedinthebuildingdesign.

Thisisapracticalguide.Completingthechecksdenedinthisguidewillnotguaranteethatabuildingmeets

eachspecicHVACcontrolrequirement.Reerencestotherelevantcodessectionsareprovidedtoshow

wheretolookoradditionaldetail,suchaswhenexceptionsareallowed.Nonetheless,perormingthechecks

inthisguidewillgoalongwaytowardensuringthatbuildingsincludeHVACcontrolscapableoprovidinga

comortableandhealthyenvironment,whilereducingenergywaste.

Lets Begin!

Forbothplansreviewandinspection,theprocessbeginswithidentiyingthebasiccharacteristicsothe

HVACdesign.Theguresbelowshowwhichsystemcharacteristicsmustbeunderstoodinordertodetermine

whichcoderequirementsapplytothebuilding.Alookatthemechanicalfoorplanwillprobablybeenough

totraceyourwaythroughtheguresandarriveattheapplicablerequirements.Youcanthenjumptothe

correspondingcolorcodedsectionsothisguide.Eachsectionexplainstherequirementanddescribesa

methodorcheckingcomplianceatplansreviewandatinspection.

Note:Theguresandcontrolsequencespresentedinthisguideareexamplesowhatcodeocials

maynd.Theyarenotintendedtobeusedordesignpurposes.


5/46

How to Use this Guide 5

Prescriptive An approach to satisying the code requirements under which the design and construction

must comply with the specic system and equipment parameters set orth in the code. This contrasts with

the perormance approach to compliance, under which a certain amount o fexibility in those parameters is

allowed, so long as the building utilizes less energy than a reerence design.

Simple system A system that utilizes actory-assembled HVAC equipment, called packaged or unitary

equipment. In a simple system, one such unit is assigned to each zone. The exception to this is that the IECC also

allows a heat-only system serving multiple zones to qualiy as a simple system.

Complex system Also sometimes reerred to as built-up, these systems include various components chiller,

cooling tower, boilers, pumps, ans, and more that are assembled on site to orm the building HVAC system.

Once assembled, the system may serve multiple zones with heating and cooling.

Thermostatic control

of heating & cooling

Commercial building

Prescriptive

Path?

Prescriptive requirements

for Complex Systems

Simple system?

Control requirements

for All Systems

Ventilation

Performance Path

Heat pump

supplemental heater

Supply fan

motor control

Yes

No

Yes

No

Humidity control


for Simple Systems

p

p

p

p

p

p

p

p

p


6/46

6 How to Use this Guide

Hydronic Using water. A hydronic system is one

that circulates heated or chilled water through a loop

to provide comort in a zone or to provide the heat

source or sink or HVAC equipment.

Zones Portions o a building served with heating,

cooling and ventilation. Zones have similar HVAC

requirements and can thereore be served with a

single thermostat or set o sensors and a single

control strategy.

End

water loopdesigned for over

300 kBtu/hr?

Economizers

Yes

No


for Simple Systems

Hydronic systemsp

p

p


7/46

How to Use this Guide 7

VAV fans

End

Multi-zone?

Water loop

serves heat pump(s)

or water-cooledA/C?

Water loop(s)?

Prescriptive requirements

for Complex Systems

Economizers

Humidity control

Hydronic heat pump

and A/C systems

Hydronic systems

No

No

Yes

Yes

Yes

No

Fan speed control for heat

rejection equipmentMulti-zone systems

pp

p

p

p

p

p

p


8/46

8 How to Use this Guide


9/46

Code Requirements and

Compliance Checks


10/46

10 Performance Path

PfPt

Manybuildingenergycodesallowbuildingstosatisythecoderequirementseitherbymeetingeachspecic

requirementorbydemonstratingthatthebuildingperormsaswellorbetterthanareerencebuilding

designthatsatisesthespecicrequirements.BothASHRAE90.1andtheIECCoeraperormancepath

tocompliance.However,evenbuildingsollowingtheperormancepathmustmeetsomemandatoryrequirementsrelatingtoHVACcontrols.

Thermostaticcontroloheatingandcoolingandcontroloventilationarerequiredorallbuildings;asare

somecontrolsrelatingtosupplementalheatersinheatpumps,humidityandcommissioning.Thesenearly

universalrequirementsarediscussedintheollowingsectiononcontrolrequirementsorallsystems.Later

sectionsturntorequirementsthatmaynotbesatisedbybuildingstakingtheperormancepath.


11/46

Control Requirements for All Systems 11

ctrqtfasyt

Thermostatic Control of Heating and CoolingThermostaticcontrolsarerequiredineachconditionedbuildingzone.Thesedevicesmustbecapableo

settingthezonestargettemperatureorheatingandcooling.Theymustalsopreventsimultaneousheating

andcoolingothezoneandalloworarangeoallowabletemperatures,knownasadeadband,inwhichneitherheatingnorcoolingisprovided.Finally,thethermostaticcontrolsmustallowthesystemtoschedule

unoccupiedperiodsandoccupiedperiods,allowingorasystemstartupperiodbetween.Duringthe

unoccupiedperiod,heatingandcoolingtargettemperaturescanbesetbacktoconserveenergybyallowinga

greaterrangeospacetemperatures.

Plan ReviewSuggestedComplianceCheck(s):

Checkmechanicalfoorplanstoveriythatthereisatleastone

thermostatperdistinctoccupancyarea(gure1).

Reviewthemechanicalfoorplansandmechanicalscheduletolocatecontrolsequencesandveriy

thatthedesignengineerhasspecieddeadband,setbackandschedulingcapabilities(gures2-4).*

*Ithebuildingisequippedwithabuildingautomationsystem(BAS),thenthesecapabilitieswillmostlikelybe

providedbytheBAS.TheBASspecicationsormanualshouldindicatethattherequiredcapabilitiesarepresent.


12/46

12 Control Requirements for All Systems

F:Mechanicalfoorplanshowingthermostatsinmultiplelocations

F:Controldiagramorvariableairvolume(VAV)boxdemonstrating5degreedeadband

ZoneTemperatureControlSequence

Heatingsetpoint(70F),adjustable

Coolingsetpoint(75F),adjustable

Deadbando5Fshallbemaintained

betweenheatingandcoolingsetpoints

min

100

70 75

Zone Temperature (F)

AirFlow(

%)

F:Samplecontrolsequenceshowingsetbackcapabilities

UnoccupiedMode:

1. Airhandlingunitsandterminalunitswillgotounoccupiedmodewhenroomoccupancysensorsand

scheduleprogramdenethezone(s)servedtobeunoccupied.

2. Zonetemperaturesetpointwillresetto55F(heatingmode)and85F(coolingmode).

3. Outsideairdamperinclosedposition.


13/46


F:Samplecontrolsequenceshowingoptimumstartcapabilities

OptimumStart:Thesystemshallcalculatethetimerequiredtobringzonesromtheunoccupiedtemperature

andhumidityconditiontooccupiedcondition.Thistimeshallbeusedtoschedulethewarm-up/cool-down

periodsuchthatoccupiedconditionsareachievedjustpriortothescheduledoccupiedperiod.

Building InspectionSuggestedComplianceCheck(s):

Veriythatprogrammablethermostatsandtemperatureandhumiditysensorshave

beeninstalledasshownintheapprovedmechanicalplans(gure5and7).

Conrmthattheinstalledthermostatshavedeadbandandsetbackcapabilities.Single

setpointthermostatswithaheat/cool/autosettingdonotcomply(gure6).

F:Temperaturesensor,asmaybeinstalledinabuildingwithabuildingautomationsystem

F:Programmablethermostat,asmaybeinstalledinbuildingusingpackagedHVACequipment


14/46


F:BASscreenshotshowingtemperaturesensorsmeasuringzonetemperatures

Additional Detail:

a) Zoning

Eachzoneisrequiredtohaveadedicatedtemperaturecontroldevice.ItheHVACsystemisdesignedtoregulatehumidity,theneachzonemustalsohaveahumiditycontroldevice.

cst

iecc ashrae

2009:503.2.4.1 2007:6.4.3.1.1

2012:403.2.4.1 2010:6.4.3.1.1

b) Deadband

Temperaturecontrolsoreachzoneshallbecapableoprovidingarangeo5degreesabove/belowsetpointwhennoheating/coolingoccurs.Forexample,asetpointo70Forheatingand75Forcooling

providesa5degreedeadbandwherenoheatingorcoolingwilloccur.

cst

iecc ashrae

2009:503.2.4.2 2007:6.4.3.2,6.4.3.1.2

2012:403.2.4.2 2010:6.4.3.2,6.4.3.1.2

c) Thermostaticsetbackcapabilities

Setbackcontrolsmustbeabletosetbacktemperaturesduringunoccupiedtimesto55orheatingand

85For90Forcooling.

cst

iecc ashrae

2009:503.2.4.3.1 2007:6.4.3.3.2

2012:403.2.4.3.1 2010:6.4.3.3.2


15/46


d) Automaticsetbackandshutdowncapabilities

Programmablethermostatsshallbecapableodierentprogramsordierentdailyoccupancyschedules.

Theymustalsoretaininormationduringpoweroutageor10hoursandhaveatemporarymanual

overrideoption.

cst

iecc ashrae

2009:503.2.4.3.2 2007:6.4.3.3.1

2012:403.2.4.3.2 2010:6.4.3.3.1

e) Optimumstartcontrols

Thesystemcontrolsshallbecapableovaryingthestarttimetobringeachspaceuptosetpoint

immediatelypriortoscheduledoccupancy.Thisoptimumstartcapabilityrecognizesthatthesystemwill

requireavariableamountotimetobringzonestocomortableconditions,dependingonthebuildings

unoccupiedconditionandtheweather.Systemswithacapacitylessthan10,000CFMmaybeexempt

romthisrequirement.

cst

iecc ashrae

2009:NA 2007:6.4.3.3.3

2012:403.2.4.3.3 2010:6.4.3.3.3

) Zoneisolation

WheremultiplezonesareservedbyacommonHVACsystem,butwillbeoccupiedondierentschedules,

thesystemmustincludecontrolsthatallowtheunoccupiedzonestobeautomaticallyisolated.When

isolated,theHVACsystemwillneithersupplynorexhaustairromtheunoccupiedzones.

cst

iecc ashrae

2009:NA 2007:6.4.3.3.4

2012:NA 2010:6.4.3.3.4

Supply Fan Motor ControlASHRAE90.1-2010introducedanewrequirementorvariableairfowcontrolsintheollowingtypeso

equipment:

Airhandlingandancoilunitsservedbychilledwaterandhavingasupplyanmotorlargerthan5hp.

Unitsservingasinglezoneandhavingdirectexpansioncoolingcapacityomorethan110,000Btu/h.

Suchequipmentisrequiredtousetwospeedmotorsorvariable-speeddrivesonthesupplyan.


16/46



Reviewtheanscheduletoseethatlargeans(5hpandlarger)are

speciedwithvariablespeeddrivesortwospeedmotors.

F:FanscheduleindicatingVSDtobeprovided

Fanschedule

ID Area Type Drive CFMT.S.P.

(inH2O)

Basiso

Design

MaxWt.

(lbs)

Electrical

ControlVolt/Ph HP

PF-1 Stair Utility

set

Belt 8000 0.5 400 480/3 7.5 VFD

PF-4 Elevator Utility

set

Belt 10000 0.5 400 480/3 7.5 VFD

SF-1 Oce Vane

axial

Belt 35000 200 480/3 40 VFD

RF-1 AHU-1 Vane

axial

Belt 20000 200 480/3 25 VFD


Veriythatsupplyanswithmotorsgreaterorequalto5hphavebeenprovidedwithVSDs(or

otherspeedcontroldevices)asindicatedonthemechanicalplans.Supplyansmaybelocated

onrootops(simplesystems)ormechanicalrooms(complexsystems)(gure9).Abuilding

automationsystem(BAS)mayalsoshowwhereequipmentiscontrolledbyaVSD(gure10).


17/46


F:VSDinstalledonasupplyan

F:BASscreenshotindicatingVSDcontrolosupplyan

cst

iecc ashrae

2009:NA 2007:NA

2012:NA 2010:6.4.3.10

VentilationThebasicrequirementocontrolsrelatingtoventilationisthattheybecapableoreducingorshuttingdown

ventilationwhenitisnotrequired.Manysystemsarerequiredtohavemotorizedsupplyairandexhaust

dampersthatautomaticallyopenwhenthezoneservedisscheduledtobeoccupiedandclosewhenthezone

isscheduledtobeunoccupied.Systemswithlargeventilationrequirementsmustalsobecapableovarying

theamountoventilationaccordingwiththerealtimeneedsothezone.


18/46


Plans ReviewSuggestedComplianceCheck(s):

Ithebuildingistallerthanthreestoriesandinclimatezones4through8,

veriythatmotorizeddampersarespeciedoroutsideairandexhaust/

reliedampersonthemechanicalfoorplansormechanicalschedule.

Reviewthemechanicalfoorplansandmechanicalscheduletolocatecontrolsequencesandveriythatthedesignengineerhasdenedaprocedurewherebydamperswill

beclosedandanswillbeshutowhenzonesareunoccupied(gure11).

Forlargespaces(greaterthan500t2),checkthemechanicalandelectricalfoor

planstoseethatCO2orothersensorsarespeciedandtiedintothecontrol

systemtoenabledemandcontrolventilation(DCV)(gure12).

F:Samplecontrolsequenceshowingdampercontrol

OutsideAirDamperControl:Outsideairintakedampersshallopeninresponsetoastartsignal.Thedampersshallcloseandtheanshallstopinresponsetoanyotheollowing:stopsignal,lossocontrolsignal,losso

electricalpower,ortheAHUsupplyanmotorstops.

F:SamplecontrolsequenceindicatingDCV

DemandControloVentilation:Duringoccupiedmode,zonerequestsorventilationshallbedeterminedbased

onsignalsromzone-locatedCO2sensors.AzoneshallrequestventilationwhentheCO2concentrationexceeds

900ppm.Inresponsetoarequestorventilation,thesystemshallrstincreasetheterminalunitairfow.I

additionalventilationisrequired,thesystemshallthenincreasetheoutdoorairrateattheairhandler.


Veriythatoutsideairandexhaust/reliedampershaveactuatorsthatautomaticallyopenandclosethe

dampersandthatthedampersareintheclosedpositioninspacesthatareunoccupied(gure13).

VeriythatCO2sensorsincludedinthemechanicalplansorthepurposeodemandcontrolventilationhavebeeninstalledasshownintheplans(gure14).

Reviewthemechanicalplansandveriythatautomaticcontrols(i.e.occupancysensoror

manualtimers)havebeenprovidedorventilationanslargerthan3/4hpasshown.


19/46


F:Motorizeddamper

F:TopviewoCO2sensor(coinorscale)

Additional Detail:

a) Dampers

Outdoorairsupplyandexhaust/relieductsshallhavemotorizeddampersthatautomaticallyclosewhen

thespacesthattheyservearenotoccupied.Buildingslessthanthreestoriestallorinclimatezones1

through3mayusegravitydampers.

cst

iecc ashrae

2009:503.2.4.4 2007:6.4.3.4.3,

6.4.3.4.1,6.4.3.4.2

2012:403.2.4.4 2010:6.4.3.4.2,6.4.3.4.1

b) Ventilationancontrols

Fanswithmotorsgreaterorequaltothree-quarterhorsepower,musthavecontrolsthatcanshutoans

whennotrequired.Thiscontrolmaybeanoccupancysensor,timer,orotherdevice.

cst

iecc ashrae

2009:NA 2007:6.4.3.4.5

2012:NA 2010:6.4.3.4.4


20/46


c) Demandcontrolventilation

Acontrolstrategythatvariestheminimumventilationoutdoorairbasedonoccupancyisrequiredor

large,denselyoccupiedspaces.Thisusuallyappliestospaces500squareeetandlargerthathave

anoccupantloadgreaterthanorequalto40peopleper1,000squareeet(IECC2012expandedthe

applicabilitybyreducingthethresholdoccupantloadto25peopleper1000squareeet).Typically,

ventilationiscontrolledbyvaryingtheoutdoorairintakebasedonthemeasuredlevelocarbondioxide

withinaspace.

cst

iecc ashrae

2009:503.2.5.1 2007:6.4.3.9

2012:403.2.5.1 2010:6.4.3.9

d) Heatrecoveryventilationbypass

Iaheatrecoveryventilator(HRV)isinstalled,thisHRVmustnotinhibittheoperationotheeconomizer.This

canbeaccomplishedthroughcontrolswhichallowtheHRVtobebypassedwhentheeconomizerisworking

cst

iecc ashrae

2009:503.2.6 2007:6.5.6.1

2012:403.2.6 2010:6.5.6.1

Heat Pump Supplemental HeaterIthebuildinghasheatpumpswithsupplementalelectricheaters,thosesupplementalheatersshouldnot

beengageduntiltheheatpumpsheatingcapacityisexceeded.ASHRAE90.1exemptsheatpumpsthatare

regulatedundertheNationalApplianceEnergyConservationAct(thosewithacoolingcapacitylessthan

65,000Btu/h)romthisrequirement.


Veriythatthemechanicalscheduleorcontrolsequencespeciesthatsupplemental

resistanceheatingcannotoperatewhentheheatpumpcanmeettheheatingload.Thismay

beaccomplishedbyspeciyingamulti-stageelectronicthermostatprogrammedtoinitiate

thesupplementalheaterwhentheheatpumpcannotmeetthesetpoint(gure15).

F:Sampleheatpumpcontrolsequenceshowingauxiliaryheatengagedassecondstage

m cfat sthtPp dvat

Heat None H Reversingvalveinheatposition

Stage1heat H,H1 Heatusingcompressor

Stage2heat H,H1,H2 Heatusingcompressorandauxiliaryheater


21/46



Checkthatthetypeothermostatorbuildingautomationsystemspecied

intheapprovedmechanicalsubmittalisinstalledandoperating.

Additional Detail:

cstiecc ashrae

2009:503.2.4.1.1 2007:6.4.3.5

2012:403.2.4.1.1 2010:6.4.3.5


22/46

22 Prescriptive Requirements for Simple Systems

Pptvrqtfspsyt

EconomizersEconomizersarerequiredinmostbuildingstoallowtheHVACsystemtoincreasetheamountooutside

airsuppliedtothezoneidoingsowillreduceenergyconsumption.Thisispossible,orexample,whenthe

zoneisbeingcooledandtheoutsideairiscoolenoughtomeetpartothatcoolingdemand.Controlotheeconomizershouldallowittovarythesupplyooutsideairromtheminimumrequiredventilationto100

percentoutsideair,basedontheconditionothezoneandtheoutsideair.Insimplesystems,theeconomizer

islikelytobeintegratedinpackagedorunitaryHVACequipment.Thus,theeconomizercontrolstrategyis

likelytobeoundinthespecicationsorthatequipment.


Checkthemechanicalscheduletoveriythateconomizersarespeciedorsystems

thatarelargerthanthethresholdsshowninthetablebelow(gure16).

IECC2009 54,000Btu/hinallclimatezonesexcept1A,1B,2A,7,and8

IECC2012 33,000Btu/hinallclimatezonesexcept1Aand1B

ASHRAE2007 65,000Btu/hinclimatezones3B,3C,4B,4C,5B,5Cand6B

135,000Btu/hinclimatezones2B,5A,6A,7and8

ASHRAE2010 54,000Btu/hinallclimatezonesexcept1Aand1B

Locatecontrolsequencesandveriythattheeconomizercontrol

sequencemeetstheollowingrequirements(gure17):

1) Thesupplyooutsideairvariesromtheminimumrequirementto100percent.

2) Economizersaresequencedwiththemechanicalcoolingequipmentandcontinueto

unctionuntiltheshut-oconditiondescribedinrequirement4,below,isreached.

3) Economizersarenotcontrolledonlybymixedairtemperature.


23/46

Prescriptive Requirements for Simple Systems 23

4) Thesupplyooutsideairisreducedtothedesignminimum

whenoneotheollowingconditionsapplies:

Outsideairtemperatureexceeds:

75Finclimatezones1B,2B,3B,3C,4B,4C,5B,5C,6B,7,or8

70Finclimatezones5A,6A,or7A

65Finanyotherclimatezone

Theclimatespecicshutoconditionisreached,asdeterminedbyanother

approvedapproachromthecodesectionsreerencedinsectioncbelow.

F:Economizerspeciedonmechanicalschedule

ahut

Symbol

LocationServed

AHU-1

1stFloorOces

SupplyFan Type Centriugal

Conguration FanCoilAirfow(CFM) 6,000

Minairfow(CFM) 6,000

Minoutsideair(CFM) 600

HP:Motor 5

Voltage/Phase 460/3

Control ON/OFF

Isolation Internal

CoolingCapacity NominalTons 15

Total(MBH) 171Sensible(MBH) 137

EDB(F) 76

EWB(F) 63

LDB(F) 55

LWB(F) 54

CWFlow(GPM) 30.0

ENTWaterTemp(F) 44.0

LVGWaterTemp(F) 56.0

Heating Type NoneWeight LBS 3,000

UnitElectrical MCA 8.3

Voltage/Phase 460/3

BasisoDesign Manuacturer Trane

Model TSeries

Notes 1

NOTE: Provide with factory installed 0100% economizer controls without barometric relief.


24/46

24 Prescriptive Requirements for Simple Systems

F:Economizercontrolsequence

AHU 1&2AutomaticDampers

OutsideAirDamper

Modulating

ClosedwhenAHUisnotoperating.

Controlledbyspacetemperature,timeoday,outsideairtemperature,andventilationrequirement

Economizercycle:

Operateswhenoutsideairtemperatureis


25/46

Prescriptive Requirements for Simple Systems 25

b) Controlstrategy

Economizersmustnotbecontrolledonlybymixedairtemperatureandmustbeabletobesequenced

withmechanicalcoolingequipment.ASHRAEprovidesanexceptionorsystemscontrolledromspace

temperature,suchassinglezonesystems.

cst

iecc ashrae

2009:NA 2007:6.5.1.1.2

2012:403.1.1.2 2010:6.5.1.1.2

c) Highlimitshuto

Whenincreaseinoutdoorairwillnolongerreducecoolingenergyuse,economizersmustbeableto

reduceoutdoorairtothedesignminimum.

cst

iecc ashrae

2009:NA 2007:6.5.1.1.32012:403.3.1.1.3 2010:6.5.1.1.3

Hydronic SystemsTherequirementsorhydronicsystemsmainlyapplytobuildingswithacomplex,builtupHVACdesign.

However,theIECCincludessomecontrolrequirementsorlarge(>300,000Btu/h)systemsthatare

categorizedassimplesystems.Oneexampleosuchasystemisaboilerloopthatsupplieshotwateror

radiantheatinginalargeapartmentbuilding.Suchsimple,butlargehydronicsystemsarerequiredtocomply

withtheapplicablehydronicsystemcontrolsthatarediscussedinthenextsectionothisguide.

Additional Detail:cst

iecc ashrae

2009:503.3.2 2007:NA

2012:403.3.2 2010:NA


26/46

26 Control Requirements for Complex Systems

ctrqtfcpxsyt

EconomizersTherequirementsoreconomizersincomplexsystemsaresimilartothoseorsimplesystems.Theeconomizer

mustvarythesupplyooutsideairromtheminimumrequiredventilationto100percentoutsideair,based

ontheconditionothezoneandtheoutsideair.Despitethissimilarity,therearetworeasonsorprovidingaseparatediscussionoeconomizersorcomplexsystems.First,thereisanadditionalrequirementorcomplex

systemsthattheuseotheeconomizershouldnotincreasebuildingheating.Second,thespecicationothe

economizerinthedesignsubmittalislikelytolooksomewhatdierentandthereorethecompliancecheck

willbeslightlydierent.


Checkthemechanicalscheduletoveriythateconomizersarespeciedor

systemsthatarelargerthanthethresholdsshowninthetablebelow.

IECC2009 54,000Btu/hinallclimatezonesexcept1A,1B,2A,7,and8

IECC2012 33,000Btu/hinallclimatezonesexcept1Aand1B

ASHRAE2007 65,000Btu/hinclimatezones3B,3C,4B,4C,5B,5Cand6B

135,000Btu/hinclimatezones2B,5A,6A,7and8

ASHRAE2010 54,000Btu/hinallclimatezonesexcept1Aand1B

Locatecontrolsequencesandveriythattheeconomizercontrol

sequencemeetstheollowingrequirements(gure19).*

1) Thesupplyooutsideairvariesromtheminimumrequirementto100percent.

2) Economizersaresequencedwiththemechanicalcoolingequipment.

3) Economizersarenotcontrolledonlybymixedairtemperature.


27/46

Control Requirements for Complex Systems 27

4) Thesupplyooutsideairisreducedtothedesignminimum

whenoneotheollowingconditionsapplies:

Outsideairtemperatureexceeds:

75Finclimatezones1B,2B,3B,3C,4B,4C,5B,5C,6B,7,or8

70Finclimatezones5A,6A,or7A

65Finanyotherclimatezone

Theclimatespecicshutoconditionisreached,asdeterminedbyanother

approvedapproachromthecodesectionsreerencedinsectioncbelow.

5) Theeconomizerwillreduceoutsideairtotheminimumrequirementwhenoutside

airnolongerprovidescoolingorwhenthesystemisinaheatingmode.



F:Economizercontrolstrategyshowninacontrolsequence

ModulatingEconomizer

ControlspositionoadamperbasedontheControlState,OutsideAirTemperature(OAT),andCooling

Demand.

Economizeravailablei:

Coolingmodeandanon

Econ.lowlimittempSP


28/46


Additional Detail:

a) Rangeooperation

Economizersshallbecapableooperatingat100percentoutsideair,eveniadditionalmechanicalcoolingis

requiredtomeetthecoolingloadothebuilding.Thisstrategyisknownasintegratedeconomizercontrol.

cst

iecc ashrae2009:503.4.1 2007:6.5.1.3

2012:403.4.1.1 2010:6.5.1.3

b) Systemintegration

Economizersshouldbeusedorcooling,evenisupplementalmechanicalcoolingisrequired.

cst

iecc ashrae

2009:NA 2007:6.5.1.32012:403.4.1.3 2010:6.5.1.3

c) Highlimitshuto

Whenincreaseinoutdoorairwillnolongerreducecoolingenergyuse,economizersmustbeableto

reduceoutdoorairtothedesignminimum.

cst

iecc ashrae

2009:NA 2007:6.5.1.1.3

2012:NA 2010:6.5.1.1.3

d) Heatingimpact

Useotheeconomizermustnotresultinanincreaseduseobuildingheat.

cst

iecc ashrae

2009:NA 2007:6.5.1.4

2012:403.4.1.4 2010:6.5.1.4

Variable Air Volume (VAV) FansVAVanswithmotorslargerthan10hp(7.5hpunderIECC2012),mustbedrivenbyvariablespeeddrives,

usevane-axialanswithvariable-pitchblades,orincorporatecontrolssuchthatmotorsuseatmost30%

othedesignanpowerwhenthesystemdelivers50%othedesignairvolume.Themostcommonmeans

omeetingthisprovisioniswithavariablespeeddrivecontrolledbyastaticpressuresensorlocatedinthe

supplyairduct.Thepressuremeasuredbythesensorisusedtosetthespeedothedrive,andthesensor


29/46


mustbepositionedwelldowntheductromtheantoprovidegoodeedback.Asheatingorcoolingdemand

decreasesinthezonesserved,thedampersthatcontrolthesupplyoconditionedairtothosezoneswill

begintoclose.Astheyclose,thepressureintheductincreases.Thesensormeasuresthisincreaseandsignals

thedrivetoslowuntilthestaticpressuresetpointisachieved.

Whenthezonedampersarecontrolledbydigitalcontrols,thesystemeciencyshouldbeurtherincreased

byresettingthestaticpressuresetpointpressurelower,untilthedamperservingthezonewiththegreatest

demandisalmostullyopen.ThecontroloVAVansthroughthismethodisanimportantandsomewhat

complicatedpartotheHVACcontroldesignstrategy.However,veriyingcompliancewiththecode

requirementsrequiresonlyaewsteps.


CheckthemechanicalfoorplanandmechanicalscheduletoseethatlargeVAVansare

speciedwithVSDsorarevane-axialanswithvariable-pitchblades(gure20).

Iadirectdigitalcontrol(DDC)systemisspeciedontheplans,thenlocatecontrol

sequencesandveriythatthedesignengineerhasdenedapressureresetstrategy.Inthestrategy,thespeedothedrive,otenstatedasapercentage,shouldberelated

totheoperationoaremotelylocatedzoneboxorterminalunit(gure21).*

Checkthemechanicalandelectricalfoorplanstoveriythatapressuresensorisspecied

tobelocatedinthesupplyairduct,wellawayromthesupplyan(gure22).



F:VSDspeciedonmechanicalschedule

Remarks

SplitsystemHVACunit,suspendedairhandler,maxheight48

Hotwaterheatingcoilwith2-waycontrolvalvesizedorcoilperormance

Variable frequency drive supply fan with variable air volume pressure control

100%outdoorairintegratedeconomizerwithdierentialdrybulbcontrol

Airfowmeter

FactoryinstalledDDCcontrolswithselectableprotocol

Remotecontrolsinterace Premiumeciencymotors

Lowleakagedampers


30/46


F:Pressureresetstrategyshownincontrolsequence

SupplyFanControlviaStaticPressureControl:ControllershallmodulatesupplyanVFDspeedtomaintain

staticpressuresetpoint.

Initialstaticpressuresetpointshallbe0.75inH2O.

AHUcontrollersshallbenetworkedwiththeirassociatedterminalunits.

Thestaticpressuresetpointshallberesetlower,untilallairfowrequestsaresatisedandthedamperononeterminalunitiswideopen.

TheDDCcontrollershallmodulateanspeedtomaintaintheductstaticpressuresetpoint.Asductpressure

decreases,anspeedwillincrease.Asductpressureincreases,anspeedwilldecrease.

F:IllustrationoVSD(hereVFD)controlbasedonstaticpressuresensorandzonedampers


VeriythatVSDs(orvariablepitchvane-axialans)havebeen

installedasshownintheapprovedmechanicaldesign.

Conrmthatstaticpressuresensor(s)havebeeninstalledasshownintheapprovedmechanicaldesign.

Ithecontrolsequenceintheapprovedsubmittalincludedstaticpressure

reset,checkthatthecorrespondingcontrolsystem(mostlikelyabuilding

automationsystem)isinstalledandoperational(gure23).


31/46


F:BASscreenshotindicatingcontroloVSDcontrollingsupplyanbasedonstaticpressure

Additional Detail:

a) VAVancontrol

IndividualVAVansgreaterthanorequalto10horsepowerinsizemusthaveaVSD,avane-axialanwith

variable-pitchblades,orothermeanstocontrolairfowthatuse30%orlessothedesignanpowerto

deliver50%othedesignairfow.Systemswithdigitalcontrolorindividualzonesmustresetthedrive

speedtomeettheneedothezonerequiringthehighestsupplyanpressure.TheIECC2012expanded

theapplicabilitybyreducingthethresholdansizeto7.5horsepower.

cst

iecc ashrae

2009:503.4.2 2007:6.5.3.2.1

2012:403.4.2 2010:6.5.3.2.1

b) Staticpressuresensorlocation

WherestaticpressuresensorsareusedtocontrolVAVans,theymustbepositionedsothatthepressure

setpointbasedonthesensorisnomorethanone-thirdthetotaldesignstaticpressureothesupplyan.

Typically,thismeansthesensormustbepositionedclosertothearthestzonesuppliedthantothean.

Eachmajorductbranchshouldhaveatleastonesensor.

cst

iecc ashrae

2009:NA 2007:6.5.3.2.2

2012:403.4.2.1 2010:6.5.3.2.2


32/46


c) VAVanpressureresetstrategy

Idirectdigitalcontroloindividualzoneboxesreportstocentralcontrolpanel,thenastaticpressure

resetstrategymustbeincludedinthecontrols.Resetmusttobebasedonthezonerequiringthe

highestsupplypressure.

cst

iecc ashrae

2009:503.4.2 2007:6.5.3.2.3

2012:403.4.2.2 2010:6.5.3.2.3

Humidity ControlWherehumidiersordehumidiersareprovided,thesystemmustcontroltheiroperationtoprevent

simultaneoushumidicationanddehumidicationandtoshutothecomponentswhentheyarenotrequired


Ithesystemhasahumidierwithapreheatjacket,thenconrmonthemechanicalfoor

planthatavalveisshownonthehotwatersupplylineeedingthepreheatjacket.

Veriythatcontrolothepreheatvalveisdescribedasanoteon

eitherthemechanicalscheduleormechanicalplans.*

Veriythatthecontrolsequencespeciesameanstoprevent

simultaneoushumidicationanddehumidication.*


providedbytheBAS.TheBASspecicationsormanualshouldindicatethattherequiredcapabilitiesarepresent


Whereapplicable,veriythatanautomaticvalvehasbeeninstalledonhumidierpreheatjackets.

Veriythatsimultaneoushumidicationanddehumidicationhasbeenpreventedin

accordancewiththeapproachdenedintheapprovedmechanicaldesign.

Additional Detail:

a) Humidiershuto

Humidierswithpreheatingjacketsmountedintheairstreamshallbeprovidedwithanautomaticvalveto

shutopreheatwhenhumidicationisnotrequired.


33/46


cst

iecc ashrae

2009:NA 2007:6.4.3.6

2010:6.4.3.6 2012:NA

b) Simultaneoushumidication/dehumidication

Limitswitches,mechanicalstops,orothermeansocontrol,suchasasequenceooperations,mustbeincludedthatarecapableopreventingsimultaneoushumidicationanddehumidication.

cst

iecc ashrae

2009:NA 2007:6.4.3.7

2012:NA 2010:6.4.3.7

Hydronic SystemsHVACsystemsotenoperateatpeakcapacityoronlyasmallportionotheheatingandcoolingseason.

Energycodesrequirethathydronicsystemsbeprovidedwithcontrolstoreducethesystemsenergy

consumptionwhenoperatingatlessthanpeakcapacity.Thisisachievedthroughequipmentsequencing,

reducingthepumpingofuidthroughthesystem,andbyresettingthetemperatureothehotwaterand

chilledwatersupply.


Reviewtheboilerspecicationsinthemechanicalscheduletoveriythatlarge

boilersarerequiredtohavemultistagedormodulatingburners.

Imultipleboilersarespecied,checkthecontrolspecicationstoconrm

thattheywillbelinkedtoacommoncontrolsystem(gure24).*

Forlargesystems(seeadditionaldetailsbelow),checkmechanicalschedulestoveriythat

VSDsormulti-stagedpumpsareprovidedorthepumps.Dierentialpressuresensors

shouldalsobespecied,toprovidethenecessaryeedbacktothecontrols(gure25).

Reviewcontrolsequencestoensurethatasupplywatertemperatureresetisincluded(gure26).*

Forheatedandchilledwatersystemswithoneshareddistributionnetwork(a2-pipesystem),reviewcontrolsequencestoveriythatthesystemdoesnotswitchbetween

heatingandcoolingwithoutanoutsideairtemperaturechangeoatleast15degrees

andthatcontrolscanpreventsuchaswitchwithouta4hourinterval(gure27).*

Veriythatlanguageisincludedincontrolsequencesorboilersandchillersto

reducefowthroughtheplantwhencapacityisreduced(gure28).*


34/46




F:Samplecontrolsequenceindicatingthatboilersaresequencedandmodulate

HotWaterPumpOperation:

Pumpsoperateinlead/lagashion.

Uponinitiationosystemoperation,startleadpump.

LeadpumpVFDspeedmodulatestomaintainheatingwatersystemdierentialpressuresetpoint

(20psid,adjustable).

Duringlowloadcondition,fowismaintainedthroughleadboileratalltimes.

Isolationvalveonstandbyboilerisclosedwhenstandbyboileriso.

F:Sampleboilerpumpsequenceooperationsdemonstratingvariablefowcapabilities/VSD

BoilerSequencing:

WhenfowissensedromAtoBinthecrossoverline,theDDCshallstartprimaryboilerandhotwaterpump.

Manuacturercontrolswillmodulatetheburnervalvetomaintainboilerhotwatertemperature.

WhenloadincreasestothepointthatfowisagainsensedromAtoBinthecrossoverline,theDDCshallstart

standbyboiler.

Asloaddecreases,theDDCshallstageboilersoinreverseorder.

F:Samplecontrolsequenceindicatingsupplywatertemperatureisreset

ChilledWaterSetpoint(CHWST)Reset

ThedeaultCHWSTis44F.

Whenthespeedsopumpsonthesecondaryloopareattheminimum,startCHWSTreset.

CHWSTwillberesetproportionallybetween48Fand42F:

48F;allcoolingcoilvalvesarelessthan90%open.

42F;3+coolingcoilvalvesaremorethan90%open.

ContinueCHWSTresetuntilthespeedooneormorepumpsonthesecondaryloopexceedstheminimum.


35/46


F:Illustratedcontrolsequenceortwopipechangeover

F:Samplecontrolsequenceorpumpisolation

ChilledWaterPumpSequencing:

InCoolingMode,DDCshallstartonesystempumpwhichshallruncontinuously.

Systempumpvariablespeeddrivewillmodulatetomaintainthedierentialpressuresetpoint(20psid,

adjustable).

Secondsystempumpwillstartithedierentialpressureallsbelowthesetpoint.

Whenbothpumpsoperate,theyshallmodulateatthesamespeedtoachievethedierentialpressuresetpoint.

Whenthesystemfowallsto50%odesignfow,thesecondpumpshallturno.


Conrmthatmultipleboilersareconnectedtoacommoncontrolsystem,suchas

abuildingautomationsystem,andthatboilerswithgreaterthan500,000btu/h

capacityareequippedwithmultistageormodulatingboilers(gure29).

Conrmthatpumpspeedcontrols(e.g.variablespeeddriveormultiple-stagedpumps)shown

intheapprovedmechanicaldesignhavebeeninstalledonallpumps(gure30).

Veriythattemperaturesensorshavebeeninstalledonchilledwatersupply,chilled

waterreturn,hotwatersupplyandhotwaterreturnpipes(gure31).

Veriythattheapprovedapproachorcontrollingsupplywatertemperaturereset,

typicallyabuildingautomationsystem,isinstalledandoperational(gure31).


36/46


F:Linkedboilercontrollers

F:Multiplepumpswithfowcontrol

F:BASshowingtemperaturesensorsonsupplyandreturnpiping

Additional Detail:

a) Boilersequencing

Heatingsystemsmadeupomultipleboilersmustbeabletobesequenced,suchthatboilerscanbe

automaticallyshutoastheyarenolongerneededtomeettheheatingrequirement.Similarly,systems

withonelargeboiler(greaterthan500,000btu/hinputcapacity)musthaveaburnerthatiseither

multistagedormodulating.


37/46


cst

iecc ashrae

2009:503.4.3 2007:NA

2012:403.4.3 2010:NA

b) Variablefow

BothIECCandASHRAErequirecontrolscapableoreducingpumpfowinlargehydronicsystemsbyatleast50%usingVSDsormulti-stagepumpswhenthesystemisoperatingunderpartloadconditions.

However,thethresholdoapplicationdiers.IECCrequiressuchcontrolsorsystemswithcapacitygreater

orequalto300,000Btu/h.ASHRAErequiresthecontrolsorsystemswithindividualpumpmotorslarger

than5horsepowerortotalpumpsystempowergreaterthan10horsepower.

cst

iecc ashrae

2009:503.4.3.4(2) 2007:6.5.4.1

2012:403.4.3.4(2)

2010:6.5.4.1

c) Supplywatertemperaturereset

Systemswithadesignheatingorcoolingcapacitygreaterthan300,000Btu/hmustincludecontrols

capableoresettingthesupplywatertemperatureaccordingtotheheatingorcoolingdemand.Thereturn

watertemperatureoroutsideairtemperaturemayserveasindicatorsothisdemand.ASHRAEprovides

anexceptionorvariablefowsystems.

cst

iecc ashrae

2009:503.4.3.4 2007:6.5.4.3

2012:403.4.3.4 2010:6.5.4.3

d) Two-pipechangeover

Systemsthatprovideheatedandchilledwatertozonesusingasinglesupplyandreturnloopmusthave

controlsthatpreventtheinitiationoheatingwithinourhoursocooling,orthereverse.Inaddition,

thechangeromheatingtocooling,orthereverse,shouldbeseparatedbyadierenceinoutsideair

temperatureoatleast15degrees.Theheatedandchilledwatersupplytemperaturesatchangeover

shouldbelessthan30Fapart.

cst

iecc ashrae

2009:503.4.3.2 2007:6.5.2.2.2

2012:403.4.3.2 2010:6.5.2.2.2


38/46


e) Pumpisolation

Chilledwaterandboilerplantswithmultiplechillersorboilersmustbeabletoreducefowthroughsystem

whenachillerorboileristurnedo.

cst

iecc ashrae

2009:503.4.3.5 2007:6.5.4.2

2012:403.4.3.5 2010:6.5.4.2

Hydronic Heat Pump and Unitary Air Conditioning SystemsSystemsthatemployawaterlooptoprovideasourceorsinkoheatorheatpumpsorunitaryairconditioners

arerequiredtohavecontrolstovarythefowowaterthroughthesystemasaunctionodemand.


Reviewthepipingdiagramtoveriythattwopositionvalvesareshownonthewaterloopo

hydronicheatpumpsandwater-cooledairconditionersthatcanshutocirculationowater

tothecompressoroeachindividualheatpumporairconditioningunit(gure32).

Veriythatthecontrolsequencesallowawatersupplytemperaturedeadbando20F

betweeninitiationoheatrejectionandheatadditiononthewaterloop.*

Reviewthemechanicalplanstoveriythatwhenthesystemisnotincoolingmodecirculation

owatertothetowerwillbepreventedbyanautomaticvalveoracontrolledpump,orthat

positiveclosuredampersareprovidedtostopaircirculationthroughaclosedcircuittower.

Checkmechanicalscheduleorcontrolsequencestoveriythatthepumpsserving

hydronicheatpumpwaterloopshavebeenprovidedwithVSDs.



F:Illustrationoheatpumppipingshowinglocationotwopositionvalves


39/46



Veriythattwopositionvalveshavebeeninstalledonhydronicheatpumpsandwatercooled

airconditioners,asshownontheapprovedmechanicalpipingdiagram(gure33).

Veriythatthepumpsservinghydronicheatpumpwaterloopshavebeen

providedwithVSDs,whereshownontheapprovedmechanicalplans.

Veriythatheatlossthroughcoolingtowersiscontrolledusingautomaticvalves,pumps,

orpositiveclosuredampers,asshownintheapprovedmechanicaldesign.

F:Twoposition(open/close)valvewithelectricactuator

Additional Detail:

a) Two-positionvalve

IECC2012requirestwopositionvalvesonhydronicheatpumpswherethetotalhydronicsystempump

powerisgreaterthan10hp.

ASHRAErequirestwopositionvalvesonhydronicheatpumpsandwatercooledairconditioners.ASHRAE

2007providesanexceptionwhentotalhydronicsystempumppowerislessthan5hp.

cst

iecc ashrae

2009:NA 2007:6.5.4.4.1

2012:403.4.3.3.3 2010:6.5.4.4.1

b) Deadband

Hydronicheatpumpwaterloopsshallhavecontrolsthatcanprovideawatersupplytemperaturedeadband

oatleast20degreesFbetweeninitiationoheatrejection(coolingtower)andheataddition(boiler).

cst

iecc ashrae

2009:503.4.3.3.1 2007:6.5.2.2.3(a)

2012:403.4.3.3.1 2010:6.5.2.2.3(a)


40/46


c) Heatrejection

Topreventexcessivehydronicloopheatloss,controloheatrejectionequipment(i.e.coolingtowers)

isrequiredorclimatezones3-8.Thiscontrolcanbeachievedusinganautomaticvalvetobypassthe

towerorbyturningothecirculationpumponanopen-circuittowerservingaheatexchanger.For

closed-circuittowers,itcanalsobeachievedwithlowleakagepositiveclosuredampersthatpreventair

circulationthroughthetower.Inzones5-8,theIECCrequiresuseoaheatexchanger,circulationpump,

andanautomaticvalve.

cst

iecc ashrae

2009:503.4.3.3.2 2007:6.5.2.2.3(b)

2012:403.4.3.3.2 2010:6.5.2.2.3(b)

d) Variablespeedcontrol

ASHRAE2010reducedthethresholdorrequiringvariablespeedcontrolisrequiredonhydronicheat

pumpandunitaryairconditionerwaterloopstoatotalpumpsystempowero5hp.Thisislowerthanthe

10hpthresholdthatappliestoalltypesohydronicsystems.

cst

iecc ashrae

2009:NA 2007:NA

2012:NA 2010:6.5.4.4.2

Fan Speed Control for Heat Rejection EquipmentControlsarerequiredonlargeansusedincoolingtowersandaircooledcondensers.Eachanpoweredby

amotoro7.5hporlargermusthaveadevice(e.g.VSD)thatcancontrolanspeed.Fanspeedmustcontrol

eitherthetemperatureothefuidleavingtheheatrejectiondeviceorthecondensingtemperatureotheheat

rejectiondevice.


Reviewthemechanicalscheduletoveriythatanswithmotor7.5hporgreateris

providedwithaVSD(orothermeans)toreduceanspeed(gure34).

Reviewthecontrolsequencestoveriythatanspeedisusedtocontroltheleaving

temperatureothefuidorthecondensingtemperatureorpressure(gure35).*




41/46


F:MechanicalscheduleshowingcoolingtoweransequippedwithVSD

coolingToWer

Symbol

LocationServed

CT-1

Chiller

HeatRejection Tons 800

Type Cells 1

Discharge Vertical

Fluid EWT(F) 90

LWT(F) 77

Flow(GPM) 1,500

Ambient(F) 67

Nozzle(tWG) 4

Fluid Water

Fan Type Axial

Number 1

Airfow(CFM) 170,000

MotorHP 25

Control VFD

Voltage/Phase 460/3

BasinHeater Number 1

Capacity 12

Voltage/Phase 460/3

PipeConnections Supply(in) 10

Return(in) 14

Make-up(in) 2Drain(in) 1

Overfow(in) 3

Weight LBS 31,000

BasisoDesign Manuacturer ABCInc

Model ModelXYZ

Notes

F:Samplenoteonmechanicalschedule

NOTE: CoolingtoweranVFDmodulatesspeedtomaintaincondensingwatertemperaturesetpoint.


42/46



Veriythatans7.5hpandgreaterhavebeenprovidedwithdevices

oranspeedcontrol(e.g.VSD)(gure36).

Conrmthatthemeansocontrollinganspeedidentiedintheapprovedmechanical

design,typicallyabuildingautomationsystem,hasbeeninstalledandisoperational.

F:Coolingtowermotor checkorconnectiontoVSD

Additional Detail:

cst

iecc ashrae

2009:503.4.4 2007:6.5.5.2

2012:403.4.4 2010:6.5.5.2

Multi-zone SystemsLargebuildingstypicallyhaveHVACsystemsthatcanheat,cool,reheat,andrecoolairmovingtomultiple

zonesatthesametime.Multiple-zonesystemsmusthaveVAVcontrolscapableoreducingthesupplyairto

anyzonebeorereheating,recooling,ormixingwarmandcoolairstreams.IECC2012requiresthesupplyair

tobereducedto30%omaximum,to300CFM,ortothelevelrequiredorminimumventilationbeoreany

reheating,recoolingormixing.TherequirementsoASHRAEaresimilar,thoughsystemsshowntoreduce

annualenergyusebyprovidingmoresupplyairareallowed.ASHRAE2010alsointroducesamethodor

systemswithdigitalcontrolozoneboxestocontroltheoutdoorairintakebasedonthezoneventilation

eciency theeciencyatwhichthesystemdeliversoutsideairtothebreathingzone.


VeriythatcontrolsequencesincludelanguageorVAVsystemoptimization

(i.e.indicatethatsupplyairisreducedpriortoreheating/recooling):

SingleductVAVsystemsshouldreducesupplyairbeorereheating/recoolingtakesplace


43/46


DualductVAVsystemsshouldminimizetheamountohot/coldairmixingbyreducingfow(gure37)

Veriythatlanguageorsupplyairtemperatureresetisincludedincontrolsequences(gure38)

F:SamplecontrolsequenceordualductVAVsystem

OccupiedMode

Cooling

Fullcooling:Colddeckairdamperopenstothemaximumposition.

Ascoolingloaddecreases,colddeckairdampermodulatesmoreclosed.

Nocallorcooling:Colddeckairdamperclosestotheminimumposition.

Heating

Fullheating:Hotdeckairdamperopenstothemaximumposition.

Asheatingloaddecreases,hotdeckairdampermodulatesmoreclosed.

Nocallorheating:Hotdeckairdamperclosestotheminimumposition.


44/46


F:Samplecontrolsequenceorsupplyairtemperaturereset

SupplyAirTemperatureReset

Whenoccupied,thesupplyairtemperature

(SAT)isresetrom53Fto65Fusingthe

ollowinglogic:

Whentheoutsideairtemperature(OAT)is70Fandabove,SATshallbe53F.

WhenOATis65Fto70F,theSATis

resetbasedonsystemdemandbetween

minimumandmaximumvaluesthatvary

linearlywithtemperature(seegure).

WhenOATisbelow65F,resetSAT

between55Fand65Fbasedonsystem

demand.

Systemdemandisdeterminedusingatrim

andrespondlogic:

Whentheaniso,SATisat65F Whentheanison,every2minutes:

IncreasetheSATsetpointby0.2Fitherearenozonecoolingrequests*

Itherearemorethantwocoolingrequests,decreasethesetpointby0.3F

*coolingrequestsaregeneratedwhenthecoolingloopoanyzoneservedis>99%

Source: EnergyDesignResources, Advanced Variable Air Volume System Design Guide, March 2007

53F

55F

65F

65F 70F

OAT

SATSetpopint


Conrmthatthebuildingautomationsystemspeciedintheapproveddesignisinstalledandoperational.

Checkingthatmulti-zoneVAVsystemsareoptimizedisanintensiveprocedure,well

beyondthescopeobuildinginspection.However,ASHRAE90.1-2010andIECC2012

requirecommissioningtobeperormedonmanycommercialbuildings.Thecommissioning

providersreportshoulddescribehowthesystemwastestedandoptimized.

Additional Details:

a) MultizoneVAVsystemoptimizationcontrol

Systemswithdigitalcontrolozoneboxesmustautomaticallyadjustsupplyairinresponsetochanges

insystemventilationeciency.Thisapproachallowsoutsideairsupplytobeprovidedatbelowdesign

rates,solongasthezonethatisleasteectiveindeliveringoutsideairtothebreathingzonemaintains

acceptableindoorairquality.DetailedguidanceonthisapproachisprovidedinASHRAEStandard62.1.


45/46

cst

iecc ashrae

2009:NA 2007:NA

2012:NA 2010:6.5.3.3

b) SingleductVAVsystems

TerminalUnitsshallreducesupplyosupplyairto30%omaximum,to300CFM,ortoalevelsucienttoprovidetheminimumrequiredventilationbeorereheating/recooling.

cst

iecc ashrae

2009:503.4.5.1 2007:-6.5.2.1

2012:403.4.5.1 2010:6.5.2.1

c) DualductVAVsystems

Dualductsystemsshallhaveterminalunitsthatcanminimizefowromoneductto30%omaximum,to300CFM,ortoalevelsucienttoprovidetheminimumrequiredventilationpriortomixingromsecondduct.

cst

iecc ashrae

2009:503.4.5.2 2007:6.5.2,1

2012:403.4.5.2 2010:6.5.2.1

d) Supplyairtemperaturereset

Supplyairtemperature(SAT)resetisrequiredormultizoneHVACsystems.SATmustberesetinresponse

tobuildingloadoroutsideairtemperature.ThecontrolsmustallowSATresetthatisatleast25percento

thedierencebetweenthedesignSATandroomairtemperature.

cst

iecc ashrae

2009:503.4.5.4 2007:NA

2012:403.4.5.4 2010:6.5.3.4


46/46

eereiftct

1-877-EERE-INFO(1-877-337-3463)www.eere.energy.gov/inormationcenter

Building Technology Program

The U.S. Department of Energys Building Energy

Codes Program is an information resource on

national model energy codes. We work with other

government agencies, state and local jurisdictions

national code organizations, and industry to

promote stronger building energy codes and help

states adopt, implement, and enforce those codes.

BECP Website

wwwyv

BECP Technical Support

tppt@bpv

wwwyv/ppt/pkpp

HVAC Guide Final Low

Documents