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BuildingTechnologiesProgram
hVacctg
fPexBipt
September 2011
at:
EricMakela,PNNL
JamesRussell,PECI
SarahFujita,PECI
CindyStrecker,PECI
PreparedbyPacicNorthwestNationalLaboratory
ortheU.S.DepartmentoEnergyBuildingTechnologiesProgram
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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
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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.
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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.
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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
Control requirements
for Simple Systems
p
p
p
p
p
p
p
p
p
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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
Control requirements
for Simple Systems
Hydronic systemsp
p
p
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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
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8 How to Use this Guide
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Code Requirements and
Compliance Checks
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10 Performance Path
PfPt
Manybuildingenergycodesallowbuildingstosatisythecoderequirementseitherbymeetingeachspecic
requirementorbydemonstratingthatthebuildingperormsaswellorbetterthanareerencebuilding
designthatsatisesthespecicrequirements.BothASHRAE90.1andtheIECCoeraperormancepath
tocompliance.However,evenbuildingsollowingtheperormancepathmustmeetsomemandatoryrequirementsrelatingtoHVACcontrols.
Thermostaticcontroloheatingandcoolingandcontroloventilationarerequiredorallbuildings;asare
somecontrolsrelatingtosupplementalheatersinheatpumps,humidityandcommissioning.Thesenearly
universalrequirementsarediscussedintheollowingsectiononcontrolrequirementsorallsystems.Later
sectionsturntorequirementsthatmaynotbesatisedbybuildingstakingtheperormancepath.
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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.
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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.
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Control Requirements for All Systems 13
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
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14 Control Requirements for All Systems
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
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Control Requirements for All Systems 15
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.
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16 Control Requirements for All Systems
Plan ReviewSuggestedComplianceCheck(s):
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
Building InspectionSuggestedComplianceCheck(s):
Veriythatsupplyanswithmotorsgreaterorequalto5hphavebeenprovidedwithVSDs(or
otherspeedcontroldevices)asindicatedonthemechanicalplans.Supplyansmaybelocated
onrootops(simplesystems)ormechanicalrooms(complexsystems)(gure9).Abuilding
automationsystem(BAS)mayalsoshowwhereequipmentiscontrolledbyaVSD(gure10).
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Control Requirements for All Systems 17
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.
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18 Control Requirements for All Systems
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.
Building InspectionSuggestedComplianceCheck(s):
Veriythatoutsideairandexhaust/reliedampershaveactuatorsthatautomaticallyopenandclosethe
dampersandthatthedampersareintheclosedpositioninspacesthatareunoccupied(gure13).
VeriythatCO2sensorsincludedinthemechanicalplansorthepurposeodemandcontrolventilationhavebeeninstalledasshownintheplans(gure14).
Reviewthemechanicalplansandveriythatautomaticcontrols(i.e.occupancysensoror
manualtimers)havebeenprovidedorventilationanslargerthan3/4hpasshown.
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Control Requirements for All Systems 19
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
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20 Control Requirements for All Systems
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.
Plan ReviewSuggestedComplianceCheck(s):
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
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Control Requirements for All Systems 21
Building InspectionSuggestedComplianceCheck(s):
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
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22 Prescriptive Requirements for Simple Systems
Pptvrqtfspsyt
EconomizersEconomizersarerequiredinmostbuildingstoallowtheHVACsystemtoincreasetheamountooutside
airsuppliedtothezoneidoingsowillreduceenergyconsumption.Thisispossible,orexample,whenthe
zoneisbeingcooledandtheoutsideairiscoolenoughtomeetpartothatcoolingdemand.Controlotheeconomizershouldallowittovarythesupplyooutsideairromtheminimumrequiredventilationto100
percentoutsideair,basedontheconditionothezoneandtheoutsideair.Insimplesystems,theeconomizer
islikelytobeintegratedinpackagedorunitaryHVACequipment.Thus,theeconomizercontrolstrategyis
likelytobeoundinthespecicationsorthatequipment.
Plan ReviewSuggestedComplianceCheck(s):
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.
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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.
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24 Prescriptive Requirements for Simple Systems
F:Economizercontrolsequence
AHU 1&2AutomaticDampers
OutsideAirDamper
Modulating
ClosedwhenAHUisnotoperating.
Controlledbyspacetemperature,timeoday,outsideairtemperature,andventilationrequirement
Economizercycle:
Operateswhenoutsideairtemperatureis
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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
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26 Control Requirements for Complex Systems
ctrqtfcpxsyt
EconomizersTherequirementsoreconomizersincomplexsystemsaresimilartothoseorsimplesystems.Theeconomizer
mustvarythesupplyooutsideairromtheminimumrequiredventilationto100percentoutsideair,based
ontheconditionothezoneandtheoutsideair.Despitethissimilarity,therearetworeasonsorprovidingaseparatediscussionoeconomizersorcomplexsystems.First,thereisanadditionalrequirementorcomplex
systemsthattheuseotheeconomizershouldnotincreasebuildingheating.Second,thespecicationothe
economizerinthedesignsubmittalislikelytolooksomewhatdierentandthereorethecompliancecheck
willbeslightlydierent.
Plan ReviewSuggestedComplianceCheck(s):
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.
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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.
*Ithebuildingisequippedwithabuildingautomationsystem(BAS),thenthesecapabilitieswillmostlikelybe
providedbytheBAS.TheBASspecicationsormanualshouldindicatethattherequiredcapabilitiesarepresent.
F:Economizercontrolstrategyshowninacontrolsequence
ModulatingEconomizer
ControlspositionoadamperbasedontheControlState,OutsideAirTemperature(OAT),andCooling
Demand.
Economizeravailablei:
Coolingmodeandanon
Econ.lowlimittempSP
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28 Control Requirements for Complex Systems
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
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Control Requirements for Complex Systems 29
mustbepositionedwelldowntheductromtheantoprovidegoodeedback.Asheatingorcoolingdemand
decreasesinthezonesserved,thedampersthatcontrolthesupplyoconditionedairtothosezoneswill
begintoclose.Astheyclose,thepressureintheductincreases.Thesensormeasuresthisincreaseandsignals
thedrivetoslowuntilthestaticpressuresetpointisachieved.
Whenthezonedampersarecontrolledbydigitalcontrols,thesystemeciencyshouldbeurtherincreased
byresettingthestaticpressuresetpointpressurelower,untilthedamperservingthezonewiththegreatest
demandisalmostullyopen.ThecontroloVAVansthroughthismethodisanimportantandsomewhat
complicatedpartotheHVACcontroldesignstrategy.However,veriyingcompliancewiththecode
requirementsrequiresonlyaewsteps.
Plan ReviewSuggestedComplianceCheck(s):
CheckthemechanicalfoorplanandmechanicalscheduletoseethatlargeVAVansare
speciedwithVSDsorarevane-axialanswithvariable-pitchblades(gure20).
Iadirectdigitalcontrol(DDC)systemisspeciedontheplans,thenlocatecontrol
sequencesandveriythatthedesignengineerhasdenedapressureresetstrategy.Inthestrategy,thespeedothedrive,otenstatedasapercentage,shouldberelated
totheoperationoaremotelylocatedzoneboxorterminalunit(gure21).*
Checkthemechanicalandelectricalfoorplanstoveriythatapressuresensorisspecied
tobelocatedinthesupplyairduct,wellawayromthesupplyan(gure22).
*Ithebuildingisequippedwithabuildingautomationsystem(BAS),thenthesecapabilitieswillmostlikelybe
providedbytheBAS.TheBASspecicationsormanualshouldindicatethattherequiredcapabilitiesarepresent.
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
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30 Control Requirements for Complex Systems
F:Pressureresetstrategyshownincontrolsequence
SupplyFanControlviaStaticPressureControl:ControllershallmodulatesupplyanVFDspeedtomaintain
staticpressuresetpoint.
Initialstaticpressuresetpointshallbe0.75inH2O.
AHUcontrollersshallbenetworkedwiththeirassociatedterminalunits.
Thestaticpressuresetpointshallberesetlower,untilallairfowrequestsaresatisedandthedamperononeterminalunitiswideopen.
TheDDCcontrollershallmodulateanspeedtomaintaintheductstaticpressuresetpoint.Asductpressure
decreases,anspeedwillincrease.Asductpressureincreases,anspeedwilldecrease.
F:IllustrationoVSD(hereVFD)controlbasedonstaticpressuresensorandzonedampers
Building InspectionSuggestedComplianceCheck(s):
VeriythatVSDs(orvariablepitchvane-axialans)havebeen
installedasshownintheapprovedmechanicaldesign.
Conrmthatstaticpressuresensor(s)havebeeninstalledasshownintheapprovedmechanicaldesign.
Ithecontrolsequenceintheapprovedsubmittalincludedstaticpressure
reset,checkthatthecorrespondingcontrolsystem(mostlikelyabuilding
automationsystem)isinstalledandoperational(gure23).
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Control Requirements for Complex Systems 31
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
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32 Control Requirements for Complex Systems
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
Plan ReviewSuggestedComplianceCheck(s):
Ithesystemhasahumidierwithapreheatjacket,thenconrmonthemechanicalfoor
planthatavalveisshownonthehotwatersupplylineeedingthepreheatjacket.
Veriythatcontrolothepreheatvalveisdescribedasanoteon
eitherthemechanicalscheduleormechanicalplans.*
Veriythatthecontrolsequencespeciesameanstoprevent
simultaneoushumidicationanddehumidication.*
*Ithebuildingisequippedwithabuildingautomationsystem(BAS),thenthesecapabilitieswillmostlikelybe
providedbytheBAS.TheBASspecicationsormanualshouldindicatethattherequiredcapabilitiesarepresent
Building InspectionSuggestedComplianceCheck(s):
Whereapplicable,veriythatanautomaticvalvehasbeeninstalledonhumidierpreheatjackets.
Veriythatsimultaneoushumidicationanddehumidicationhasbeenpreventedin
accordancewiththeapproachdenedintheapprovedmechanicaldesign.
Additional Detail:
a) Humidiershuto
Humidierswithpreheatingjacketsmountedintheairstreamshallbeprovidedwithanautomaticvalveto
shutopreheatwhenhumidicationisnotrequired.
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Control Requirements for Complex Systems 33
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.
Plan ReviewSuggestedComplianceCheck(s):
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).*
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34 Control Requirements for Complex Systems
*Ithebuildingisequippedwithabuildingautomationsystem(BAS),thenthesecapabilitieswillmostlikelybe
providedbytheBAS.TheBASspecicationsormanualshouldindicatethattherequiredcapabilitiesarepresent.
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.
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Control Requirements for Complex Systems 35
F:Illustratedcontrolsequenceortwopipechangeover
F:Samplecontrolsequenceorpumpisolation
ChilledWaterPumpSequencing:
InCoolingMode,DDCshallstartonesystempumpwhichshallruncontinuously.
Systempumpvariablespeeddrivewillmodulatetomaintainthedierentialpressuresetpoint(20psid,
adjustable).
Secondsystempumpwillstartithedierentialpressureallsbelowthesetpoint.
Whenbothpumpsoperate,theyshallmodulateatthesamespeedtoachievethedierentialpressuresetpoint.
Whenthesystemfowallsto50%odesignfow,thesecondpumpshallturno.
Building InspectionSuggestedComplianceCheck(s):
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).
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36 Control Requirements for Complex Systems
F:Linkedboilercontrollers
F:Multiplepumpswithfowcontrol
F:BASshowingtemperaturesensorsonsupplyandreturnpiping
Additional Detail:
a) Boilersequencing
Heatingsystemsmadeupomultipleboilersmustbeabletobesequenced,suchthatboilerscanbe
automaticallyshutoastheyarenolongerneededtomeettheheatingrequirement.Similarly,systems
withonelargeboiler(greaterthan500,000btu/hinputcapacity)musthaveaburnerthatiseither
multistagedormodulating.
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Control Requirements for Complex Systems 37
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
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38 Control Requirements for Complex Systems
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.
Plan ReviewSuggestedComplianceCheck(s):
Reviewthepipingdiagramtoveriythattwopositionvalvesareshownonthewaterloopo
hydronicheatpumpsandwater-cooledairconditionersthatcanshutocirculationowater
tothecompressoroeachindividualheatpumporairconditioningunit(gure32).
Veriythatthecontrolsequencesallowawatersupplytemperaturedeadbando20F
betweeninitiationoheatrejectionandheatadditiononthewaterloop.*
Reviewthemechanicalplanstoveriythatwhenthesystemisnotincoolingmodecirculation
owatertothetowerwillbepreventedbyanautomaticvalveoracontrolledpump,orthat
positiveclosuredampersareprovidedtostopaircirculationthroughaclosedcircuittower.
Checkmechanicalscheduleorcontrolsequencestoveriythatthepumpsserving
hydronicheatpumpwaterloopshavebeenprovidedwithVSDs.
*Ithebuildingisequippedwithabuildingautomationsystem(BAS),thenthesecapabilitieswillmostlikelybe
providedbytheBAS.TheBASspecicationsormanualshouldindicatethattherequiredcapabilitiesarepresent
F:Illustrationoheatpumppipingshowinglocationotwopositionvalves
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Control Requirements for Complex Systems 39
Building InspectionSuggestedComplianceCheck(s):
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)
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40 Control Requirements for Complex Systems
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.
Plan ReviewSuggestedComplianceCheck(s):
Reviewthemechanicalscheduletoveriythatanswithmotor7.5hporgreateris
providedwithaVSD(orothermeans)toreduceanspeed(gure34).
Reviewthecontrolsequencestoveriythatanspeedisusedtocontroltheleaving
temperatureothefuidorthecondensingtemperatureorpressure(gure35).*
*Ithebuildingisequippedwithabuildingautomationsystem(BAS),thenthesecapabilitieswillmostlikelybe
providedbytheBAS.TheBASspecicationsormanualshouldindicatethattherequiredcapabilitiesarepresent
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Control Requirements for Complex Systems 41
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.
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42 Control Requirements for Complex Systems
Building InspectionSuggestedComplianceCheck(s):
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.
Plan ReviewSuggestedComplianceCheck(s):
VeriythatcontrolsequencesincludelanguageorVAVsystemoptimization
(i.e.indicatethatsupplyairisreducedpriortoreheating/recooling):
SingleductVAVsystemsshouldreducesupplyairbeorereheating/recoolingtakesplace
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Control Requirements for Complex Systems 43
DualductVAVsystemsshouldminimizetheamountohot/coldairmixingbyreducingfow(gure37)
Veriythatlanguageorsupplyairtemperatureresetisincludedincontrolsequences(gure38)
F:SamplecontrolsequenceordualductVAVsystem
OccupiedMode
Cooling
Fullcooling:Colddeckairdamperopenstothemaximumposition.
Ascoolingloaddecreases,colddeckairdampermodulatesmoreclosed.
Nocallorcooling:Colddeckairdamperclosestotheminimumposition.
Heating
Fullheating:Hotdeckairdamperopenstothemaximumposition.
Asheatingloaddecreases,hotdeckairdampermodulatesmoreclosed.
Nocallorheating:Hotdeckairdamperclosestotheminimumposition.
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44 Control Requirements for Complex Systems
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
Building InspectionSuggestedComplianceCheck(s):
Conrmthatthebuildingautomationsystemspeciedintheapproveddesignisinstalledandoperational.
Checkingthatmulti-zoneVAVsystemsareoptimizedisanintensiveprocedure,well
beyondthescopeobuildinginspection.However,ASHRAE90.1-2010andIECC2012
requirecommissioningtobeperormedonmanycommercialbuildings.Thecommissioning
providersreportshoulddescribehowthesystemwastestedandoptimized.
Additional Details:
a) MultizoneVAVsystemoptimizationcontrol
Systemswithdigitalcontrolozoneboxesmustautomaticallyadjustsupplyairinresponsetochanges
insystemventilationeciency.Thisapproachallowsoutsideairsupplytobeprovidedatbelowdesign
rates,solongasthezonethatisleasteectiveindeliveringoutsideairtothebreathingzonemaintains
acceptableindoorairquality.DetailedguidanceonthisapproachisprovidedinASHRAEStandard62.1.
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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
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