ApacheHVACUserGuide

IESVirtualEnvironment6.3ApacheHVACUserGuide6.3revA

VE6.3 ApacheHVAC 1

Contents1 Introduction.................................................................................................................................0H7

1.1 WhatisApacheHVACandwheredoesitfitwithintheVirtualEnvironment?.......................1H71.2 ApacheHVACInterfaceOverview..........................................................................................2H8

1.2.1 VirtualEnvironmentMenuBar...................................................................................................................3H81.2.2 ApacheHVACMenuBar..............................................................................................................................4H81.2.3 ApacheHVACToolbars................................................................................................................................5H81.2.4 ModelWorkspace.......................................................................................................................................6H81.2.5 Mousecontrols...........................................................................................................................................7H91.2.6 ViewToolbar...............................................................................................................................................8H91.2.7 Componentbrowser...................................................................................................................................9H9

1.3 AComponentbasedApproachtoSystemSimulation.........................................................10H111.4 SystemModelingFundamentals.........................................................................................11H12

1.4.1 Preparation...............................................................................................................................................12H121.4.2 ConstructingSystems...............................................................................................................................13H131.4.3 Roomcomponents....................................................................................................................................14H14

2 HVACSystemComponents........................................................................................................15H162.1.1 Watersideplantequipmentandwaterloops...........................................................................................16H162.1.2 Airsideplantequipmentandsystemcomponents...................................................................................17H162.1.3 RoomunitszoneequipmentincludedonlywithinRoomcomponents.................................................18H16

2.2 HeatSources.......................................................................................................................19H182.3 PartLoadHeatSource........................................................................................................20H19

2.3.1 Partloadheatsourcedefinition...............................................................................................................21H202.3.2 CombinedHeat,Cooling,&Power...........................................................................................................22H212.3.3 Condenserheatrecovery..........................................................................................................................23H212.3.4 Pumppower.............................................................................................................................................24H222.3.5 PartloadPerformance.............................................................................................................................25H22

2.4 HotWaterBoilers...............................................................................................................26H232.4.1 Hotwaterboilerdefinition.......................................................................................................................27H242.4.2 CombinedHeat,Cooling,&Power...........................................................................................................28H252.4.3 Condenserheatrecovery..........................................................................................................................29H252.4.4 BoilerPerformance...................................................................................................................................30H262.4.5 RatedCondition........................................................................................................................................31H312.4.6 DesignCondition.......................................................................................................................................32H342.4.7 OperatingParameters..............................................................................................................................33H352.4.8 Pumps.......................................................................................................................................................34H382.4.9 Pumpheatgaintohotwaterloop(fraction)............................................................................................35H39

2.5 Airsourceheatpump.........................................................................................................36H422.5.1 Heatpumpsettings...................................................................................................................................37H442.5.2 Heatpumpperformance..........................................................................................................................38H44

2.6 ChilledWaterLoops,HeatRejection,andChillerSequencing.............................................39H452.6.1 Chilledwaterloopdefinition....................................................................................................................40H492.6.2 ChilledWaterLooptab.............................................................................................................................41H51

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2.6.3 HeatRejectiontab....................................................................................................................................42H542.6.4 ChillerSettab............................................................................................................................................43H60

2.7 PartLoadCurveChillers......................................................................................................44H622.7.1 Partloadcurvechillerdefinition..............................................................................................................45H622.7.2 CondenserHeatRecovery........................................................................................................................46H642.7.3 Electricalpowerconsumptionforpumpsandfans..................................................................................47H652.7.4 COPTemperatureDependence................................................................................................................48H662.7.5 Partloadperformancedataforchillerandauxiliaryequipment.............................................................49H66

2.8 ElectricWatercooledChillers.............................................................................................50H682.8.1 Watercooledchillerdefinition.................................................................................................................51H682.8.2 ChillerPerformance..................................................................................................................................52H692.8.3 DesignCondition.......................................................................................................................................53H782.8.4 RatedCondition........................................................................................................................................54H80

2.9 ElectricAircooledChillers..................................................................................................55H832.9.1 Watercooledchillerdefinition.................................................................................................................56H832.9.2 ChillerPerformance..................................................................................................................................57H852.9.3 DesignCondition.......................................................................................................................................58H932.9.4 RatedCondition........................................................................................................................................59H94

2.10DedicatedWatersideEconomizers(types)..........................................................................60H972.10.1 Watersideeconomizersettingsdialog.....................................................................................................61H99

2.11DXCooling(types)............................................................................................................62H1022.12UnitaryCoolingSystems(types).......................................................................................63H105

2.12.2 UnitaryCoolingSystemPerformanceData............................................................................................64H107

2.13HeatingCoils.....................................................................................................................65H1102.14CoolingCoils.....................................................................................................................66H111

2.14.1 Background.............................................................................................................................................67H1112.14.2 SimpleModel..........................................................................................................................................68H1112.14.3 AdvancedModel.....................................................................................................................................69H1112.14.4 AutosizingMode.....................................................................................................................................70H1122.14.5 ManualMode.........................................................................................................................................71H1122.14.6 CoolingCoilDialogs................................................................................................................................72H1132.14.7 DesignSizingParametersforSimpleCoilModel....................................................................................73H1172.14.8 DesignSizingParametersforAdvancedCoilModel...............................................................................74H118

2.15SprayChamber.................................................................................................................75H1232.15.1 Reference................................................................................................................................................76H1232.15.2 SprayEfficiency.......................................................................................................................................77H1232.15.3 CirculationPumpElectricalPower..........................................................................................................78H124

2.16SteamHumidifiers............................................................................................................79H1252.17HeatRecoveryDevices......................................................................................................80H1262.18Fans..................................................................................................................................81H1282.19MixingDamperSet...........................................................................................................82H1302.20ReturnAirDamperSet......................................................................................................83H1372.21ControlledDivergentTJunction(splitterdamper).........................................................84H138

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2.22DuctworkHeatPickup.....................................................................................................85H1392.23DirectActingHeater/Cooler.............................................................................................86H1402.24HotWaterRadiators.........................................................................................................87H142

2.24.2 DistributionPumpConsumption............................................................................................................88H1462.24.3 Material..................................................................................................................................................89H1462.24.4 TotalRadiatorWeight.............................................................................................................................90H1462.24.5 WaterCapacity.......................................................................................................................................91H146

2.25ChilledCeilings.................................................................................................................92H1473 Controllers............................................................................................................................... 93H151

3.1 WorkingwithcontrollersontheairsideHVACnetwork....................................................94H1513.1.1 On/Off,Deadband,andProportionalcontrol.........................................................................................95H1523.1.2 Multiplecontrolofsinglevariable..........................................................................................................96H152

3.2 Controlleroperation.........................................................................................................97H1533.3 Controllerparameters......................................................................................................98H154

3.3.1 Controlledvariables................................................................................................................................99H1553.3.2 Sensedvariables.....................................................................................................................................100H156

3.4 Controlsincombination...................................................................................................101H1583.4.1 Multiplecontrollersatasinglenetworknode........................................................................................102H1583.4.2 LinkingofcontrollersvialogicalANDandORconnections....................................................................103H159

3.5 Airflowcontrollers............................................................................................................104H1593.6 Controllerparametersterminologyandgeneraldiscussion...........................................105H159

3.6.1 TimeSwitchorOn/OffControl...............................................................................................................106H1593.6.2 Sensor(foron/offandproportionalcontrol).........................................................................................107H1613.6.3 SetPoint(foron/offcontrol)..................................................................................................................108H1613.6.4 ProportionalControl...............................................................................................................................109H1623.6.5 ANDConnections....................................................................................................................................110H1643.6.6 ORConnections......................................................................................................................................111H164

3.7 ControllerAlgorithm.........................................................................................................112H1643.8 Airflowcontrol.................................................................................................................113H1663.9 IndependentTimeSwitchController................................................................................114H1673.10IndependentControllerwithSensor.................................................................................115H169

3.10.1 Proportionalcontrolssequencing...........................................................................................................116H172

3.11IndependentDifferentialController..................................................................................117H1743.12DependentTimeSwitchController...................................................................................118H1753.13DependentControllerwithSensor....................................................................................119H1763.14DependentDifferentialController....................................................................................120H177

4 RoomUnitControllers.............................................................................................................121H1804.1 HotWaterRadiatorControl..............................................................................................122H181

4.1.2 On/offandsetpointcontrols.................................................................................................................123H1824.1.3 ProportionalControllerforHotWaterFlowRate..................................................................................124H183

4.2 ChilledCeilingControl......................................................................................................125H1844.2.2 On/offandsetpointcontrols.................................................................................................................126H185

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4.2.3 ProportionalControllerforColdWaterFlowRate.................................................................................127H1854.2.4 ProportionalTemperatureController.....................................................................................................128H186

4.3 DirectActingRoomHeaterController...............................................................................129H1865 HVACWizard...........................................................................................................................130H188

5.1 HVACWizardInterface.....................................................................................................131H1885.1.1 HVACWizarddialog................................................................................................................................132H1885.1.2 HVACWizard:CreateNewSystem.........................................................................................................133H1895.1.3 Page3oftheHVACWizard(CreateNewSystem)..................................................................................134H1905.1.4 HVACWizard:OpenRecentSystem.......................................................................................................135H191

6 MultiplexingHVACSystemNetworks......................................................................................136H1926.1 CreatingaMultiplexOverview.......................................................................................137H193

6.1.1 RulesforMultiplexesandcontrollerswithinthem................................................................................138H196

6.2 CreateMultiplex...............................................................................................................139H1976.2.1 Description..............................................................................................................................................140H1976.2.2 EditingMode...........................................................................................................................................141H1976.2.3 Layers......................................................................................................................................................142H1986.2.4 PrincipalRooms......................................................................................................................................143H1996.2.5 AssignfromRoomGroup........................................................................................................................144H201

6.3 EditMultiplex...................................................................................................................145H2026.3.1 MultiplexToolbar...................................................................................................................................146H2026.3.2 EditMultiplexDialog...............................................................................................................................147H202

6.4 EditingComponentsandControllersinmultiplex.............................................................148H2036.4.1 TabularEditing........................................................................................................................................149H2036.4.2 TouchEdits.............................................................................................................................................150H2036.4.3 EditRoomComponentInstancesandRoomUnitControllers................................................................151H203

6.5 TabularEditing.................................................................................................................152H2046.5.2 PastetoDataTableusingtabulareditview...........................................................................................153H206

6.6 NodeNumbering..............................................................................................................154H2086.7 DeleteMultiplex...............................................................................................................155H209

7 SystemLoads,Ventilation,andAutosizing...............................................................................156H2107.1 Overview..........................................................................................................................157H2107.2 Zonelevelloadsandsizing...............................................................................................158H2107.3 Systemlevelloadsandsizing............................................................................................159H2117.4 SystemPrototypes&Sizingworkflownavigator...............................................................160H212

7.4.1 SystemPrototypes&Sizingworkflowsummary....................................................................................161H2127.4.2 Designsizingconditions..........................................................................................................................162H2157.4.3 AcquirePrototypeSystems.....................................................................................................................163H2157.4.4 PrototypeSystemsSelectionandModification......................................................................................164H2177.4.5 AssignSpacesorZonestoRoomComponents.......................................................................................165H2177.4.6 SystemSchedulesHoursofoperationandsetpoints..........................................................................166H2187.4.7 RoomLoadsCalculations........................................................................................................................167H2197.4.8 AccessLoadsDataspreadsheetsandASHRAE62.1Ventilation.............................................................168H2207.4.9 AHUSystemParameters.........................................................................................................................169H222

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7.4.10 AssignSystemParametersandRoomSizingData..................................................................................170H2237.4.11 SystemandPlantLoadsCalculation.......................................................................................................171H2247.4.12 SystemandPlantEquipmentSizing........................................................................................................172H2257.4.13 SystemandPlantSizingReport..............................................................................................................173H225

8 PrototypeHVACSystems.........................................................................................................174H2288.1 PredefinedprototypeHVACsystems:Commonfeatures.................................................175H2298.2 PredefinedprototypeHVACsystems:Systemtypesandconfigurations..........................176H2308.3 Workingwithprototypesystems......................................................................................177H233

8.3.1 Loading,saving,andretrievingprototypesystems................................................................................178H2338.3.2 Selecting,moving,copying,andnamingsystems...................................................................................179H2338.3.3 Modifyingpredefineprototypesystems...............................................................................................180H233

8.4 Commonelementsusedinpredefineprototypesystems................................................181H2338.4.1 Energyrecoveryandbypassdampersection.........................................................................................182H2338.4.2 VAVairflowcontrols...............................................................................................................................183H236

8.5 Prototypesystems:Systemspecificdescriptionsandguidance........................................184H2378.5.1 PackagedTerminalAirConditioning(PTAC)...........................................................................................185H2378.5.2 PackagedTerminalHeatPump(PTHP)...................................................................................................186H2378.5.3 Singlezoneairconditioningsystemwithfurnace(PSZAC)...................................................................187H2378.5.4 Singlezoneheatpumpsystem(PSZHP)................................................................................................188H2378.5.5 VAVreheatusingDXCoolingandHWboiler..........................................................................................189H2378.5.6 VAVusingDXCoolingandparallelfanpoweredboxeswithelectricheat.............................................190H2378.5.7 VAVreheatusingwatercooledchillerandHWboiler...........................................................................191H2378.5.8 VAVusingwatercooledchillerandparallelfanpoweredboxeswithelectricheat..............................192H2378.5.9 Dedicatedoutsideairsystem(DOAS)withfourpipefancoilunits,EWCchillerandHWboiler...........193H2378.5.10 IndirectdirectevaporativecoolingversionofVAVreheatsystem5abovewithbackupDXcoolingand

zonelevelCO2baseddemandcontrolledventilation(DCV).................................................................194H2378.5.11 VAVreheatwith differentialenthalpy economizer set up for the public areas of a hotel or similar

buildingwithPTACsystemsforindividualguest/residentroomsdrawingairfromanatriumzoneonthemainVAVsystem....................................................................................................................................195H237

8.5.12 Mixedmodenatural ventilation andVAVreheatwith zone temperature and zoneCO2overrides fornatventwhenitisinsufficient...............................................................................................................196H237

8.5.13 Singlefandualductandwithzonelevelmixingboxes..........................................................................197H2378.5.14 Dualfandualductwithzonelevelmixingboxes..................................................................................198H2378.5.15 Underfloor air distributionwith parallel fanpowered boxes for perimeter zones, leakage path, and

heatingmoderemixingofPFPbzones..................................................................................................199H2378.5.16 UFAD/DV system as above,plusheatpipeor runaround coil inAHU for free reheatof subcooled

(dehumidified)airaftertheAHUcoolingcoil.........................................................................................200H2388.5.17 Active chilled beams and DOAS for ventilation using electric watercooled chiller with waterside

economizerandcondenserheatrecovery;HWboilerandrecoveredheatforDOASandzonebaseboardfintubeconvectors.................................................................................................................................201H238

8.5.18 Radiantheatingandcoolingpanels(i.e.,fourpipesystem),plusDOASwithairsideenergyrecoveryandDCV.........................................................................................................................................................202H238

8.5.19 RadiantpanelsandDOASasabovewithheatpipeor runaroundcoil inAHU for freereheatofsubcooled(i.e.,dehumidified)airaftertheAHUcoolingcoil......................................................................203H238

9 References...............................................................................................................................204H23910AppendixA.RulesforAirFlowSpecification............................................................................205H240

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11AppendixB.HVACSystemsModelingGuidanceSpecifictoASHRAEStandard90.12007........206H24211.1.1 Baselinesystems2and4PackagedTerminalHeatPump(PTHP)andPackagedSingleZoneHeatPump

(PSZHP)..................................................................................................................................................207H242

12AppendixC.ModelingVRV/VRFsystems.................................................................................208H252

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1 0BIntroduction

1.1 12BWhatisApacheHVACandwheredoesitfitwithintheVirtualEnvironment?

ApacheHVAC is used formodeling heating, ventilating, and airconditioning (HVAC) systems, and fallswithintheVirtualEnvironmentsThermalapplicationcategory.

TheApacheHVACsupportsthedetaileddefinition,configuration,control,andmodelingofHVACsystems.ThesimulationprogramitselfisrunfromwithinApacheThermal.

ApacheHVAC is invokedasanadjunct toApacheSimulationby linking toaparticularHVAC system filewhenthebuildingmodelsimulationisrun,asdescribedintheApacheUserGuide.

TherearetwodistinctmeansofspaceconditioningandHVACsimulation intheIESVirtualEnvironment,andthesearesuitableforverydifferenttasks,levelsofanalysis,andstagesofdesign.

ApacheSystemsSimplifiedsystemmodelingforschematicdesignandcodecomplianceinApacheSim:

Fullyautosizedand ideallycontrolledsystemsconditionspacesexactly tosetpointsviapredefined HVAC systemtype algorithms andminimal room, system, and plant inputswithinApacheSim.ThissimplifiedHVACmodelingisfullyintegratedwiththethermal,solar,andbulkairflow modeling at every simulation time step. However, because the systems areapproximated, it is far less representative of actual system equipment, configurations, andcontrols.Thus,whileitmaybeveryusefulinearlydesignphasesandspaceloadsanalyses,thistype of modeling is normally not used in design development, documentation of energyperformance for theASHRAE90.1performance ratingmethod, thermal comfort studies,orotherdetailedanalysis.

ApacheHVACDetailedHVACsystemsmodeling:

Detaileddynamicmodelingofsystems,equipment,andcontrols inApacheHVAC isalso fullyintegratedwith the thermal, solar,andbulkairflowmodelingatevery simulation time step.Componentbased system models can be built from scratch or by modifying autosizableprototypesystems,ortheprototypesystemscanbeusedintheirpredefinedconfiguration.

WhenApacheHVAC is invoked,all spaces in themodel thatareassigned toa room component in theactiveApacheHVACsystematthetimeofsimulationwillbeservedbythatsystem.Solongasthisistrue,theseroomswillnotbeservedbythesimplersystemsotherwisedefined intheApacheSystemsdialog.Similarly,Auxiliaryventilation,asdefinedintheAirExchangestaboftheThermalConditionstemplate,isturnedoffautomaticallyforroomsservedbyanApacheHVACsystem.

VirtualEnvironment

Thermalapplications

ApacheHVACview

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1.2 13BApacheHVACInterfaceOverview

TheApacheHVACviewconsistsofthefollowinginterfacefeatures:

1.2.1 59BVirtualEnvironmentMenuBar

Thesemenus provide functions used throughout the Virtual environment. Please refer to the VirtualEnvironmentUserGuideforfurtherinformation.

1.2.2 60BApacheHVACMenuBar

ThesepulldownmenusprovidefunctionsspecifictotheApacheHVACview.

1.2.3 61BApacheHVACToolbars

The toolbars provide quick access tomenu functions, selection of components and controllers to beplacedon the system schematic, creation and editingof systemofmultiplexes, and access to systemprototypes.Themultiplexingeditingtoolbarisactiveonlywhenamultiplexisselected.

1.2.4 62BModelWorkspace

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Themodelworkspacedisplays theHVAC system airside schematic and provides a graphicalmeansofselecting,configuring,organizing,andeditingcomponentobjects.

1.2.5 63BMousecontrolsTheleftmousebuttonisusedforselectingandplacingcomponentandcontrollers.Whenplacingthese,thecurrentselectionpersistsuntilcancelledbyclickingtherightmousebutton.Themousescrollwheelcanbeusedtozoominandoutofthesystemsview.Thepanfunctionaccessedprovidedbymovingthemousewhiledepressingthescrollwheel.

1.2.6 64BViewToolbar

This provides functions formanipulating the view of the system schematic, including zoom to HVACnetworkextents,window,in,out,pan,previous,andnext.

1.2.7 65BComponentbrowserBrowsershow/hidetoolbarbutton.

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ThecomponentbrowserprovidesalistingofallcomponentsinthecurrentApacheHVACfile.Thiscanbe

usedtolocateand/orselectaparticulartypeofcomponentorcontrollerwithinalargeorcomplexHVACnetwork. Selecting the componentor controllerwithin thebrowser causes it tobehighlightedon thenetwork in themodel space.Thebrowser canalsobeuseful indetermininghowmanyofaparticularcomponentorcontrollertypearepresent.

ItisnotnecessarytohidethecomponentbrowserformostHVACsystemnetworks,asthespeedofthishasbeensignificantly improvedoverearlierversions.Whenworkingonexceptionally largeorcomplexHVACnetworks, if theopeningofcomponentandcontrollerdialogsdoesbegin toslownoticeably, thecomponentbrowsercanbeturnedOFFbyclickingthebrowsershow/hidebuttononthetoolbar.Thiswillfurtherincreasethespeedwithwhichcomponentandcontrollerdialogsopen.

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1.3 AComponentbasedApproachtoSystemSimulation

Energy simulationprogramshave in thepastprovidedmodelsofonlycertain fixed system types (VAV,induction,fancoils,etc).Inpractice,buildingsystemsdonotconformtotheserigidsystemtypes,andsoitwasnecessarytoacceptadegreeofcompromiseintherealismofthemodel.

Figure11:AmultizoneHVACnetworkinthiscasevariableairvolumewithindirectdirectevaporativecooling, energy recovery, variation of static pressurewith bypass of heat exchangers, duct heat gain,returnairplenums, controls formixedmodeoperationwithnatural ventilation,andprimary, transfer,andexhaustairflowpathsavailabletoeachofthezonesinthelayeredmultiplexregion.

ApacheHVAChasbeendesignedtoimposeminimalrestrictionsontheuserindefiningthesystemmodel.Theuser isofferedanumberofbasicblocks,eachdescribingagenerictypeofequipment(heatingcoil,fan, humidifier, etc.). These basic blocks can be assembled as required to model an actual systemconfiguration,ratherthanan idealizedsimplification.Thecomplexityofthemodel is limitedonlybythetypesofblockavailableandsomebasicrulesconcerningtheirinterconnection.Withintheseconstraints,itispossibletoassemblemodelsofmanydifferentsystemandcontrolconfigurationsandtoexplorethebenefitsofvariationsonstandardsystemtypes.

Anitemofplantorcontrolcanbedescribedonce,andthencopiedorreferencedasmanytimesasmayberequiredtodefinethesystem.

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1.4 14BSystemModelingFundamentals

1.4.1 66BPreparationThe speed,efficiency,andeffectivenesswithwhichanApacheHVAC systemcanbe setandall thermalzonesassignedtoitissignificantlydependentupontheextenttowhichthemodelhasbeenappropriatelyorganized prior to doing so. Therefore, it is important to complete the following inModelIt, beforeattemptingtoassignroomsorzonestoanApacheHVACsystem:

Beginbyusing theConnectSpaces tool to coupleany rooms in themodel thatwill shareacommon thermostator relatedmeansof controlling space conditions (e.g., theywill all beservedbyasingleVAVbox).Theresulting thermalzonewill thusberepresentedasasingleRoom component in ApacheHVAC. This will facilitate use of multiplexing, predefinedsystems,andefficientsystemlayout,whileavoidingunnecessarycomplexity.

o Whenconnectingspaces, iftheywillbeseparatedbyphysicalpartitions intheactualbuilding, these partitions should be retained, as their thermalmass and ability orreceive solar gain or other radiant, conductive, and convective heat transfer willcontributetotheaccuracyofthermalandenergymodeling.

o Ifanyofthezoneshasabsoluteinternalgains(WorBtu/h)ratherthaninternalgainsdefinedaccording to floorarea (W/m2orW/ft2), theabsolute gainswillhave tobemanuallyadded in thecompositezone.However, if theyareassignedperunit floorarea,noactionisrequired,asnofloorareawillbelost.

In addition to conditioned spaces, create geometry for anyother spaces or zones thatwillneedtoberepresentedinApacheHVAC,suchasreturnairplenums(typicallyoneperfloororas designed), underfloor air distribution (UFAD) supply plenums, thermally stratified zones,radiantheatingorcoolingslabs,earthtubes,solarchimneys,etc.

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It is important tosetupaGroupingScheme inModelIt thatsorts thermalzones intogroupssuchasSystem1, 2, 3,etc.orAHU1, 2, 3,etc.andotherspacetypes,suchasReturnairplenums,Solarchimneysegments,Unconditionedzones,etc.

Ifthemodel includesUFADofthermaldisplacementventilation(DV), it isessentialtoensure

that the number and order of Stratified zones exactlymatches the number and order ofcorresponding Occupied zones in any one AHU group. Doing so will facilitate systemmultiplexing,autosizing,andotherfundamentalaspectsofsystemmodeling.Iftherearesomemixed (nonstratified zones)on the same system,eitherplace them in a separate groupofoccupiedzonesorcreatedummystratifiedzones(e.g.,aseriesofsmallsuperinsulatedboxeswith no internal gains) in themodel that can fill out the list of stratified zones tomake itparallel the listofoccupiedzoneson thesamesystem.OccupiedandStratifiedshouldbe inseparategroupswiththeAHUAssignmentscheme.

1.4.2 67BConstructingSystemsSystemsareconstructedbypickingcomponents from the toolbars.Mostcomponents take the formoftiles that are placed on the diagram to build up a schematic of the system. Controllers can also bedrawn,togetherwithlinesindicatingtheassociatedsensorandcontrolpoints.Certaincomponents,suchasplantequipment,donotappearontheschematic,butareinsteadlinkedtoothercomponentsviatextreferences.

Each component has a set of parameters characterizing its operation. Facilities for editing theseparameters are accessed by doubleclicking on the component or through themenus. Once placed,groupsofcomponentsmaybeselected,deleted,moved,orcopiedusingfunctionsonthetoolbar.

Multiplexing,describedinsection6,providesanefficientmeansofassigninggroupsofspacestoasetofroom components and of replicating and editing HVAC components, controllers, and configurationsthereof.TheassociatedTabularEditviewsupportsefficientlyeditingandcheckingnumerous inputs forcomponentsandcontrollers.

Whendrawingschematicsitishelpfultokeepinmindthefollowingprinciples:

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WhenfirstbuildinganHVACsystem, it isadvisabletokeepthesystemsimple.Thismakes iteasy to test the controlprinciples involved.The system can laterbeexpanded to introduceadditionalroomsandcontrolrefinements.

Setup theminimumnumberof flow controlsnecessary todefine the flow throughout thesystemi.e., on all branches. In otherwords, airflowmust be specified in all parts of thesystem,exceptwhere the flow canbededuced fromother specified flowsby addition andsubtractionatjunctions.Specifyingmoreflowsthanarestrictlynecessaryisnotforbidden,butalwaysensurethatthespecifiedflowsaremutuallyconsistent.Inmostcases,itwillbeeasiertoallowflowstobecalculatedwherevertheycanbe.

In thecasea room, it isonlynecessary tospecifyeither thesupplyor theextract flow.Theprogramwillthensettheotherflowontheassumptionofequalityof inflowandoutflow. Inspecializedapplications,suchaswhenMacroFlo isrunning intandemwithApacheHVAC,theroom inflowandoutflowmaybeset todifferentvalues.Any imbalancebetween inflowandoutflowwillthenbepickedupbyMacroFlo(ifitisinuse),andthedifferencewillbemadeupwithflowsthroughopeningsinthebuilding.AnimbalancecanalsobemeaningfulifMacroFloisnotinuse.Forexample,ifmoreairissuppliedtoaroomthanisextracted,theexcesswillbeassumedtobeventedtooutside.ForafullaccountoftherulesforairflowspecificationseeAppendixA.

TheschematicmayincludemultipleSystemInletandSystemOutletcomponents.Thesecanbeusedtorepresentboththeairinletandoutletofamechanicalsystemandotherpaths,suchasexfiltrationinthecaseofapressurizedbuilding.

Mostcomponentsplacedontheairsidenetworkmusthaveappropriatecontrollersattachedinordertofunction.Seecomponentsectionsfordetails.

The Checknetworkbuttonwill identifymost errors in the schematic. It alsonumbers thenodes of the network, providing a reference to the nodes that is useful when viewingsimulation results. To remove the node numbering, if desired, simply reopen the sameApacheHVACfile.

DetailsofallequipmenttobeincludedinthesimulationareenteredinApacheHVAC.Theextentofdatainputdependsonthescopeofthesimulation,which isatthediscretionoftheuser.For instance if it isrequiredtocalculatethenetenergyconsumptionofanLTHWheatingcoil,itwillbenecessarytospecifyacoilandaheat source to serve it.However, itwillnotbenecessary to input thecharacteristicsof theLTHW system. In such a case the distribution lossesof the LTHW system andpumppower shouldbeenteredaszeroandtheheatsourceefficiencytakenas100%.

Notethatthedutyofequipmentforsimulationpurposescanbesetasthecomponentsareplacedorcanbeprovidedby theautosizingprocess. It isnecessaryonly tospecifyaduty thatequalsorexceedsanyrequirementsubsequentlycalledfor.

1.4.3 68BRoomcomponentsThereareanumberofimportantpointstonotewithregardtothearrangementofroomcomponentsintheairsystemandthespecificationofsupplyairflowrates:

ARoomintheVEisany3Dspacethatistobemodeledasadistinctthermalzone.Thiscanbemultiple rooms combined inModelIt as a thermal zone, a single room, or a subdividedpotionof roomvolume,suchasaperimeterzone inanopenplanspaceor theoccupiedorstratified zonewithina space servedbydisplacementventilation.TheApacheHVACRoomcomponentcanalsorefertoaspacethatwouldnotorcouldnotbeoccupied,butwhichplays

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a role in thedynamic thermal interactionwithHVAC systems.Examples includea returnairplenum,anunderfloorairdistribution(UFAD)plenum,asegmentwithinanearthtube,aspacewithin a venteddoubleskin faade,or even a concrete slab thatwillbedirectlyheatedorcooledbyahydronicloop.

Itispermissibletousethesameroomcomponentmorethanonceintheairsystemnetworkdescription,suchaswhenmorethanonesystemsuppliesairtothesameroom.Forexample,consideracasewhere room typeAhas separateair supplies forheatingandcooling; theremayonlybeoneactualroomtypeA,butwecanusetwointhesystemnetworkdescriptionone intheheatingbranchandone inthecoolingbranch.Theresult isexactlythesameas ifyouhadmixedtheheatingandcoolingsupplybranchestogetherthroughacombiningjunctionandsuppliedthismixedairtoasingleroomtypeA.Theuseofmultipleroomcomponents inthiswayreducestheneedforlargenumbersofmixinganddividingjunctions.

Oncethesystemairhasenteredaroomcomponent,theprogramassumesthattheairwithinthe room (orbounded thermalzoneassigned toa roomcomponent) is fullymixed. It isnotpossibletodifferentiatebetween,say,airenteringfromaceilingdiffuserandairenteringfromaperimeterunitoraflooroutlet.Youcan,ifyouwish,describeasingleroomasseveralroomtypesforthepurposesofthecomputersimulatione.g.,thecoreandperimeterzonesofanopenplanofficecouldbedescribedasseparateroomtypes.However,youshouldappreciatethatthereareanumberofcomplexmechanismsofheattransferinvolvedinsuchasituation(wind, stack,and inducedairmovement, radiantheatexchange,etc.)and theprogram canonlyapproximatelyanalyzesomeofthese.

Some situationsarebestmodeledbyputting two roomcomponents in series.Forexample,youmaywishtomodelabuildinginwhichthereturnairisextractedviatheceilingvoid.Thiscanbeachievedbydescribingtheoccupiedspaceandtheceilingvoidastwoseparateroomtypesandthenconnectingtheminseries.

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2 1BHVACSystemComponents

Figure21:HVACcomponentstoolbar

ApacheHVACallows18generictypesofHVACcomponentstobemodeled.

2.1.1 69BWatersideplantequipmentandwaterloops Heatsources:hotwaterboilers,heatpumps,furnaces,electricresistanceheat,etc. Chilledwaterloopswithanassociatechillerset,condenserloop,andcoolingtower Chillers:electricwatercooled,aircooledtypes;othersimilarwatercoolingsources Watersideeconomizers(asadedicatedunitoramodeforwatercooledchillersystems) Watersourceheatpumpsfortheupgradeofheatrecoveredfromacondenserloop Directexpansion(DX)cooling(1to1relationshipwithacoilontheairsidenetwork) Unitarycoolingsystems(completeunitisrepresentedbyacoilontheairsidenetwork)

2.1.2 70BAirsideplantequipmentandsystemcomponents Airsourceheatpumpscoupledtoabackupheatsource Spraychamberhumidifiers Steaminjectionhumidifiers Airtoairheat/energy/enthalpyrecoverydevices Ductworkcomponentswiththermalpropertiesformodelingheatgainorloss Fans Dampersetsincludingmixingdampersandcontrolledflowsplitters Heatingcoils Coolingcoils(simpleandadvancedmodelsforchilledwater,DX,WSE,andUCSsources) Roomcomponents(canbeassignedanygeometricspaceinthemodel)

2.1.3 71BRoomunitszoneequipmentincludedonlywithinRoomcomponents Directactingheater/coolers Radiatorsandsimilarterminalheatingdevices Chilledceilingpanels,chilledbeams,andsimilarterminalcoolingdevices

The firstsetof thesearedefinedmainly inplantequipmentdialogs.Components in themiddlesetaredealtwithmainlyontheairsidenetwork.Thelastset,roomunits,differfromotherHVACcomponentsinthat theyaredefined in termsof typesbut then locatedwithina room componentor thermal zone(including innonoccupied spaceoraheatedor cooled slab zone) rather thanon theairsidenetwork.EnergyusedbyroomunitsisalsoaccountedforandreportedseparatelyfromairsideHVACheatingandcoolingcomponents.

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Dataenteredforfansrepresentsaspecialcaseinthatfansarenotcontrolleddirectlyandfancomponentinputsareusedonlytocalculateconsequentialenergyconsumptionandeffectonairtemperature.Thevalue entered in a fan component does not determine airflow through the system. Rather, the fancomponentacts likeameterwithadefinedsetofperformancecharacteristics.Theairflowthroughthefanisdeterminedbyflowcontrollersonnetworkbranches.

Themodelingofplantcomponents isquasisteadystate inthattheprogramdoesnotattempttomodeltransient behavior between simulation time steps. However, because time steps in ApacheSim aretypicallyonly610minutes,andcanbeaslittleas1minute,ifdesired,constantplantbehavioroveratimestep is an appropriate assumption. Furthermore, there is interaction between the HVAC system andconditionedspaces(includingnaturalventilation,whenrunningMacroFlo)ateverysimulationtimestep.

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2.2 15BHeatSources

ApacheHVACofferstwotypesofheatsource:apartloadcurveheatingplantmodel,whichmaybeusedtorepresentaboiler,aheatpump,furnace,orsomeothertypeofheatingplant,andahotwaterboilermodel.BothmodelsareaccessedthroughtheHeatsourcestoolbariconshownbelow.Theheatsourceslist inFigure22 shows the currentmodel typeas part load curveheatingplant.You can choose thedesiredmodeltypetobeaddedthroughtheTypetoadddropdownselection.

Toolbariconforheatsourceslist.

Figure22:Heatsourceslistforselecting,adding,copying,andremovingbothpartloadcurveandhotwaterboilerheatingplantmodels.

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2.3 16BPartLoadHeatSource

The inputparameters for thepart load curveheatingplantmodelare introducednext in this section.Informationaboutthehotwaterboilermodelisintroducedinsection2.2.

Thepartloadcurveheatingplantmodelcanprovideheattoanycomponentsthatpresentaheatingload.These range from baseboard heaters to heating coils and including steam humidifiers and absorptionchillers(viathepartloadcurvechillerdialog).Thepartloadcurveheatingplantcanactasabackupforanairsourceheatpumportomeetremainingloadaftertheheatavailablefromacombinedheat&powersystemorcondenserheatrecovery(fromthepartloadcurvechiller,electricaircooledchiller,orelectricwatercooledchiller)hasbeenconsumed.

Theheating loadcollectivelypresentedbytheradiators,heatingcoils,etc.assignedtoaparticularheatsourcearesummedateachtimesteptosettherequiredinstantaneousoutputfromtheheatingplant.Anallowanceismadeforanypipeworkdistributionlossesthatarenotaccruingtothebuildinginterior.Partloadefficiencycharacteristicsdetermineenergyconsumptionoftheplantequipment.

Thepartloadheatingplantmodulecanoperate inconjunctionwith (asbackup for)anairsourceheatpump. The heat pumpmode is selected by placing a heat pump component on the schematic andselectingaheatingsourcefromthelistintheheatpumpdialog.

Note: if the loadonaheating source isgreater than themaximum load specified in theheatingplantdefinition, itwillsupplytheadditionalenergybuttheefficiencywillremainatthevalueenteredforfullload.

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2.3.1 72BPartloadheatsourcedefinition

Figure23:Partloadheatingplanteditingdialogshowingillustrativeinputs

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2.3.1.1 Heatingsourcereference

Enteradescriptionofthecomponent.Thereferenceislimitedto100characters.Itisforyourusewhenselecting, organizing, and referencing any component or controllers within other component andcontrollerdialogsandinthecomponentbrowsertree.Thesereferencescanbevaluableinorganizingandnavigating thesystemandwhen thesystemmodel is later reusedonanotherprojectorpassedon toanothermodeler. Reference names should thus be informativewith respect to differentiating similarequipment,components,andcontrollers.

2.3.1.2 Heatingsourcetype

ChoosefromBoiler,HeatpumporOtherheatingplant.Allthesetypesaremodeledinthesameway,buttheirsimulationresultsappearunderdifferentvariablesinVista.

2.3.1.3 Fuel

Specifythefuelused.

2.3.1.4 DistributionLosses

Enter the lossesdue toheatdistribution as apercentageofheating load. For example, ifdistributionlossesareenteredas5%andtheheatsourceisconnectedto10radiatorspresentingatotalheatingloadof20kW, thedistribution lossof0.0520kW (1kW) isadded to radiatorheatdemand togivea fuelconsumptionof21kWtheheatingplantefficiencyatthatload.

Thelossesdonotaccruetozonesinthebuilding.

2.3.1.5 Oversizingfactor

FollowingASHRAELoadsautosizing,thefactorbywhichtheheatingplantsizeisincreasedrelativetothepeakcalculatedvalue.

2.3.2 73BCombinedHeat,Cooling,&Power

2.3.2.1 BackupforCH(C)P?

Tickthisboxto indicatethat loadsservedbythisheatsourcewillbemetfirstbyavailableheatfromacombinedheat&power(CHP)orcombinedheat,cooling,andpower(CHCP)system, ifpresentonehasbeendefinedwithintheCHPsectionoftheRenewablesdialogintheApacheThermalview.

2.3.2.2 CH(C)Psequenceranking

CH(C)P sequence rankingdetermines the sequence inwhichheat sourcesare switched in tomeetanyremainingloadaftertheavailableCH(C)Pcapacityhasbeenused.Heatsourceswithlowervaluesofthisparameterwillbe switched inbefore thosewith higher values (the formerwillnormallybe themostefficient heat sources). If two heat sources have the same sequence ranking theywill be switched insimultaneously,withtheCHPinputsupplyingthesamefractionoftheheatingloadforbothsystems.

2.3.3 74BCondenserheatrecoveryCondenserheatrecoveryisincludedinbothPartloadcurveandElectricwatercooledchillermodels.Thecurrentmodelmakes a userspecified percentage of thermal energy rejected to the condenser loopavailabletoaHeatsourcecomponent.Thispercentagerepresentssimpleheatexchangereffectiveness.

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Theavailable fractionofcondenserheat is thenassigned (within thechillerdialog) toa receivingheatsourcethatwillusethisrecoveredheatfirstwhenaloadispresent.

Thetemperaturefortherecoveredcondenserheatcanbeupgradedwithanelectricwatertowaterheatpump.ThiswouldbeusedinthecasesotherthanpreheatofDHW,suchasservingwhenspaceheatingloads that requirehigher temperatures thannormallyavailableviaaheatexchangeron thecondenserwaterloop.AfuelcodeassignmentandCOPareprovidedfortheheatpump.

2.3.3.1 Usewatersourceheatpump?

Ifthewaterloopservedbytheheatingplantreceivesheatrecoveredfromachillercondenser,thisheatmaybeupgradedusingawatersourceheatpump.Specifythismodeofoperationbytickingthebox.

2.3.3.2 HeatpumpCOP

EntertheCOPofthewatersourceheatpumpthatcouplesthecondenserloopwiththehotwaterloop.

2.3.3.3 Fuel

Thefuelusedbythewatersourceheatpump.

2.3.4 75BPumppowerEnterthecirculationpumpelectricalpower.Thepumpisassumedtooperatewheneverthereisaheatingloadtobemetonthisheatsourcecircuit,irrespectiveofthesourceoftheheat(i.e.boiler,heatpumporrecovered heat from chillers). The pump power pump ismodulated by the pump usage percentagesdefinedinthepartloadtable.

2.3.5 76BPartloadPerformance

2.3.5.1 Load

Enteruptotenloadvaluestodefinethepartloadefficiencycharacteristic.

Important:Thepartloadvaluesmustbeentered in increasing(ascending)orderfromtoptobottom. Ifenteredinthereverseorder,onlythefirstvaluewithbeused.

2.3.5.2 Efficiency

Enteranefficiencyvalue foreachpartloadvalue. Linear interpolation isappliedbetween thedefinedpoints.

2.3.5.3 Pumpusage

Enter a pump usage percentage for each partload value. Linear interpolation is applied between thedefinedpoints.

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2.4 HotWaterBoilers

Thehotwaterboilermodelcanprovideheattoanycomponentsthatpresentaheatingload.Theserangefrom baseboard heaters to heating coils and even absorption chillers (via the partload curve chillerdialog).Thehotwaterboilercanactasabackupforanairsourceheatpumportomeetremainingloadaftertheheatavailablefromacombinedheat&powersystemorcondenserheatrecovery(fromthepartloadcurvechillerorelectricwatercooledchiller)hasbeenconsumed.

Theheating loadcollectivelypresentedbytheradiators,heatingcoils,etc.assignedtoaparticularheatsourcearesummedateachtimesteptosettherequiredinstantaneousoutputfromtheheatingplant.Anallowanceismadeforanypipeworkdistributionlossesthatarenotaccruingtothebuildinginterior.Partloadefficiencycharacteristicsdetermineenergyconsumptionoftheplantequipment.

Thehotwaterboilermodulecanoperate inconjunctionwith (asbackup for)anairsourceheatpump.Theheatpumpmode isselectedbyplacingaheatpumpcomponenton theschematicandselectingaheatingsourcefromthelistintheheatpumpdialog.

Themodelusesdefaultoruserdefinedboilerperformancecharacteristicsatratedconditionsalongwiththe boiler efficiency curve to determine boiler performance at design and offrated conditions, asspecifiedandsimulated,respectively.

Thehotwaterloopconfigurationisassumedtobeaprimaryonlysystem,poweredbyahotwaterpumpthat canbeeitheravariablespeedpumpwithVSDora constantspeedpump riding thepump curve.When thehotwater loop isonly servedbyhotwaterboiler (i.e.,withoutanairsourceheatpumporCH(C)Palsosupplyingheattothesamehotwaterloop),thepumpisassumedtooperateinlinewiththeboiler,subjecttotheconstraintthatthepumpwillstartcyclingbelowtheminimumflowrateitpermits.Whentheboiler issharingthehotwatercircuit loadwithotherheatsuppliers(airsourceheatpumporCH(C)P),thepumpoperationwillbeindependentoftheboileron/offcyclingstatus.

Thehotwatercircuitflowratevaries inproportiontothecircuitheating load(presentedbytheheatingcoils, hot water radiators, etc. that the circuit serves), subject to theminimum flow rate the pumppermits.Thedesignhotwaterpumppower iscalculatedas the specificpumppowermultipliedby thedesignhotwatercircuitflowrate.Itisthenmodifiedbythepumppowercurvetogettheoperatingpumppower.

Transferofhotwaterpumpheatgaintotheloopismodeledaccordingtoauserinputfractionforpumpandmotorheatgaintowaterloop.

Note: If the loadonahotwaterboilerorotherheating source isgreater than themaximum capacityspecifiedintheheatingplantdefinition,theplantmodelwillsupplytheadditionalenergy;however,theefficiencywillremainatthevalueenteredforfullload.

Note:Asteamhumidifiercannotbeservedbyahotwaterboiler,asthehotwaterboilermodelincludespumping power and returnwater temperature, and these parameterswould not be appropriate forsteam delivery. Steam humidifiersmust therefore use a heat source defined via the partload curvemodel.

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2.4.1 77BHotwaterboilerdefinition

Figure24:Hotwaterboilereditingdialog

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2.4.1.1 Reference

Enteradescriptionofthecomponent.Thereferenceislimitedto100characters.Itisforyourusewhenselecting, organizing, and referencing any component or controllers within other component andcontrollerdialogsandinthecomponentbrowsertree.Thesereferencescanbevaluableinorganizingandnavigating thesystemandwhen thesystemmodel is later reusedonanotherprojectorpassedon toanothermodeler. Reference names should thus be informativewith respect to differentiating similarequipment,components,andcontrollers.

2.4.1.2 Fuel

Enterthefueltypeusedbythehotwaterboiler.

2.4.1.3 DistributionLosses

WarningLimits(%) 0.0to20.0ErrorLimits(%) 0.0to75.0

Enterthelossesduetoheatdistributionaroundthesystemasapercentageofboilerheatdemand.Thelossesdonotaccruetospaceswithinthebuilding.

2.4.2 78BCombinedHeat,Cooling,&Power

2.4.2.1 BackupforCH(C)P?

Tickthisboxto indicatethat loadsservedbythisheatsourcewillbemetfirstbyavailableheatfromacombinedheat&power(CHP)orcombinedheat,cooling,andpower(CHCP)system, ifpresentonehasbeendefinedwithintheCHPsectionoftheRenewablesdialogintheApacheThermalview.

2.4.2.2 CH(C)Psequenceranking

CH(C)P sequence rankingdetermines the sequence inwhichheat sourcesare switched in tomeetanyremainingloadaftertheavailableCH(C)Pcapacityhasbeenused.Heatsourceswithlowervaluesofthisparameterwillbe switched inbefore thosewith higher values (the formerwillnormallybe themostefficient heat sources). If two heat sources have the same sequence ranking theywill be switched insimultaneously,withtheCHPinputsupplyingthesamefractionoftheheatingloadforbothsystems.

2.4.3 79BCondenserheatrecoveryCondenserheatrecoveryisincludedinbothPartloadcurveandElectricwatercooledchillermodels.Thecurrentmodelmakes a userspecified percentage of thermal energy rejected to the condenser loopavailabletoaHeatsourcecomponent.Thispercentagerepresentssimpleheatexchangereffectiveness.Theavailable fractionofcondenserheat is thenassigned (within thechillerdialog) toa receivingheatsourcethatwillusethisrecoveredheatfirstwhenaloadispresent.

Thetemperaturefortherecoveredcondenserheatcanbeupgradedwithanelectricwatertowaterheatpump.ThiswouldbeusedinthecasesotherthanpreheatofDHW,suchasservingwhenspaceheatingloads that requirehigher temperatures thannormallyavailableviaaheatexchangeron thecondenserwaterloop.AfuelcodeassignmentandCOPareprovidedfortheheatpump.

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2.4.3.1 Usewatersourceheatpump?

Ifthewaterloopservedbytheheatingplantreceivesheatrecoveredfromachillercondenser,thisheatmaybeupgradedusingawatersourceheatpump.Specifythismodeofoperationbytickingthebox.

2.4.3.2 HeatpumpCOP

EntertheCOPofthewatersourceheatpumpthatcouplesthecondenserloopwiththehotwaterloop.

2.4.3.3 Fuel

Thefuelusedbythewatersourceheatpump.

2.4.4 80BBoilerPerformance

2.4.4.1 BoilerModelDescription

Clickingthisbuttontopopupasummaryofthehotwaterboilermodelasshownbelow:

Figure25:Hotwaterboilermodeldescription

2.4.4.2 RatedConditionisDesignCondition

Whenthisboxisticked,thedesignconditiondata(seedetailsintheDesignconditionsubtab)isareadonlycopyofthecurrentratedconditiondata(seedetails intheRatedconditionsubtab), includinganyunsavededitsyouhavemade.

2.4.4.3 2identicalstagedboilersoperatinginparallel?

If thischeckbox is ticked, two identical stagedboilerswillbeused in thehotwater loop towhich thisboilerisassigned.Itisassumedthatthetwoidenticalboilersarearrangedinparallelandthatthedesigntemperatureriseacrosseachboiler iskeptasTbdes.Thedesignwaterflowrate inthemainhotwaterloopisthustwiceofthatdesignflowthrougheachboiler.Thedesignhotwaterpumppowerisbasedonthedesignflowrateinthemainhotwaterloop.

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If thischeckbox is ticked,youcanalso specifywhetherornot theboilerswillshare loadequallywhenbothboilersareon(seebelow).

2.4.4.4 Boilersshareloadequallywhenbothareon?

Thischeckboxonlydisplayswhenthe2identicalstagedboilersoperatinginparallel?checkboxisticked.

Ifthischeckboxisticked,itisassumedthattheboilersshareloadequallywhenbothboilersareon.Inthiscase,youcanalsospecifythepercentageofcombinedcapacityatwhichthesecondboilerswitcheson(seebelow).

If thischeckbox isunticked, the two identicalboilersareassumed tooperate instrictstaging, i.e., thefirstboilerwillbeloadedtoitsfullcapacity,thesecondboilerswitchesontotaketheremainingloadthefirstboilercannotmeet.

2.4.4.5 Percentageofcombinedcapacityatwhichsecondboilerswitcheson

This textboxonlydisplayswhen the 2 identicalstagedboilersoperating inparallel?checkboxand theBoilers share load equally when both are on? checkbox are both ticked. Usually this will be 50%(default),whichmeansthesecondboilerswitchesonwhenthefirstboilercannotmeetthe load. Ifthesecond boiler is designed to switch on before the first boiler is fully loaded, you can specify anypercentage value between 0% and 50%. For example, if this parameter is specified as 40%, then thesecondboilerwillswitchonwhenthefirstboileris80%loaded.Andwhenbothboilersareon,theywillsharethelooploadequally.

2.4.4.6 BoilerEfficiencyCurve,fEpt(p,Tlbt)

Theboilerefficiencycurvecurrentlyselected.UsetheSelectbuttontoselecttheappropriatecurvefromthesystemdatabase.

Predefinedefficiencycurves

Noncondensingboiler Condensingboiler Circa1975hightempboiler Circa1983midtempboiler Newerlowtempboiler

Thefirst,second,andlastofthepredefinedefficiencycurvesabovearethemostlikelytobeapplicableformodernhotwaterboilers.Keep inmindthatthesecurvesdescribetherelativeperformanceviatheshapeofthecurve,whereastheuser inputforEfficiencyattheratedconditionshiftstheentirecurveupordown.

UsetheEditbuttontoeditthecurveparametersifneeded.TheEditbuttonwillpopupadialogdisplayingtheformulaandparametersofthecurve,allowingthecurveparameterstobeedited.Youareallowedtoeditthecurvecoefficients,inadditiontotheapplicablerangesofthecurveindependentvariables.Wheneditingthecurveparameters,itisimportantthatyouunderstandthemeaningofthecurveanditsusageinthemodelalgorithm.

Alsobecarefulthattheeditedcurvehasreasonableapplicablerangesforthe independentvariables.Aperformancecurveisonlyvalidwithinitsapplicableranges.Inthecasetheindependentvariablesareoutoftheapplicablerangesyouset,thevariablelimits(maximumorminimum)youspecifiedintheinputwillbeapplied.

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Figure 26: Select dialog for the hot water boiler efficiency curve (part load and water tempdependence)

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Figure 27: Edit dialog for the hotwater boiler efficiency curve (part load andwater temperaturedependence)

Theboilerefficiencycurve(partloadandwatertempdependence)fEpt(p,Tlbt)isabicubicfunctionof

p=partloadratio

tlbt=TlbtTdatum

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Where

Tlbt=hotwatersupply(leavingboiler)temperature

Tdatum=datumtemperature(0Cor0F),introducedfortheconvenienceofunitsconversionofthe

curvecoefficients.

And:

fEpt(p,Tlbt)=(C00+C10p+C20p2+C30p

3+C01tlbt+C02tlbt2+C03tlbt

3

+C11ptlbt+C21p2tlbt+C12ptlbt

2)/Cnorm

where

C00,C10,C20,C30,C01,C02,C03,C11,C21,andC12arethecurvecoefficients

Cnormisadjusted(bytheprogram)tomakefEpt(1,Tlbtrat)=1

Tlbtrat=ratedhotwatersupply(leavingboiler)temperature.

The boiler efficiency curve is evaluated for each time step during the simulation. The curve value ismultipliedbytheratedefficiency(Erat)togettheoperatingefficiency(E)ofthecurrenttimestep,forthespecificpartloadratiopandTlbttemperature:

E=EratfEpt(p,Tlbt)

Thecurveshouldhaveavalueof1.0whenthepart loadratioequals1.0andtheTlbttemperature isatratedcondition.

Anoteontheapplicablerangeofpartloadratiop:

Theminimum p is used by the program as theminimum partload ratio for continuous operation,underwhichtheboilerstartscyclingonandoff.

Themaximumpshouldusuallybe1.0.Duringthesimulation,apartloadratiogreaterthan1.0isasignofboilerundersizing.

Also note that the bicubic form of the boiler efficiency curve can be used in simplified forms. Forexample, touse it inabiquadratic form, simply specifyC30,C03,C21,andC12 tobezero.Touse it inaquadraticlinearform,simplyspecifyC30,C03,C02,andC12tobezero.

2.4.4.7 ParasiticPower,Wp

Thisistheboilerparasiticpoweratfullload.ItisautomaticallyderivedbytheprogramusingtheprovidedparasiticElectricInputRatioandtheboilerdesignheatingcapacity,anddoesnotneedtobespecified.

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Theparasiticpowerrepresentstheparasiticelectricpowerconsumedbyforceddraftfans,fuelpumps,stokers,orotherelectricaldevicesassociatedwiththeboiler.Foranaturaldraftgasfiredboiler,Wpmaybe zeroor close to zero. Thisparasiticpower is consumedwhenever theboiler isoperating, and themodelassumesthatthisparasiticpowerdoesnotcontributetoheatingthewater.

2.4.4.8 ParasiticElectricInputRatio,Wp/Qdes

Enter the ratiobetween theboiler designparasitic power consumption and theboiler designheatingcapacity.Thisisusedtoderivetheboilerdesignparasiticpowerconsumptionbytheprogram.

2.4.5 81BRatedConditionRated condition and Design condition areprovided for your flexibility in specifyinghotwaterboilerdata.

Theratedcondition isthebasisforthecalculationofboilercharacteristicsatsimulationtime.Theratedcondition is usually the condition atwhich the boiler characteristics are specified by amanufacturer.However,itcanoptionallybethedesigncondition,inwhichcasetheuserselectsRated=Design.

Thedesignconditionistheconditionapplyingatthetimeofdesignpeakboilerload(butwillbeenteredmanuallyinthefirstphase).

Auserwishing tousecatalogueboilerdataentersacapacityandefficiencyat the ratedconditionandreadsoffthederivedcapacityandefficiencyatthedesigncondition.(Notethemodeltreatsthecapacityas a constant, so the design capacitywill always equal the rated capacity. Design efficiencymay bedifferentfromratedefficiencyiftheuserspecifiesadesignhotwatersupplytemperaturethatisdifferentfromtheratedhotwatersupplytemperature.)

A userwishing to size a boiler based on a design load enters a capacity and efficiency at the ratedcondition, and then adjusts the efficiency to produce the desired derived efficiency at the designcondition(allowingforamarginofoversizing).(Designcapacitywillalwaysequaltheratedcapacity.)

IftheratedconditionanddesignconditionareoneandthesametheuserticksRatedconditionisdesigncondition,whichmakesthedesignconditionadynamiccopyoftheratedcondition.

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Figure28:Hotwaterboilerdialogshowingratedconditionsubtab

2.4.5.1 HotWaterSupplyTemperature,Tlbtrat

Entertheratedhotwatersupplytemperature(leavingboilerwatertemperature).

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2.4.5.2 HotWaterFlowRate,Vbrat,Vbrat/Qrat,Tbrat

Entertheratedhotwaterflowrate.Vbrat,Vbrat/Qrat,andTbratarethreedifferentoptionsforspecifyingratedhotwaterflowrate.CurrentlyitisspecifiedintermsofTbrat(thedifferencebetweentheratedhotwater supplyand return temperatures).Theother twooptions (Vbratand the ratiobetween ratedhotwaterflowrate(Vbrat)andratedheatingcapacity(Qrat))areautomaticallyderivedbytheprogrambasedonthespecifiedTbratandcannotbeedited.

2.4.5.3 HeatingCapacity,Qrat

Entertheratedheatingcapacity.

2.4.5.4 Boilerefficiency,Erat

Enter the ratedBoilerefficiency.Theboilerefficiency (asa fractionbetween0and1) is theefficiencyrelativetothehigherheatingvalue(HHV)offuelatapartloadratioof1.0andtheratedhotwatersupplytemperature (leavingboiler).Manufacturers typically specify theefficiencyofaboilerusing thehigherheatingvalueofthefuel.Fortherarecasewhenamanufacturers(orparticulardataset)boilerefficiencyisbasedon the lowerheatingvalue (LHV)of the fuel,multiply the thermalefficiencyby the lowertohigher heating value ratio. For example, assume a fuels lower and higher heating values areapproximately45,450and50,000kJ/kg, respectively.Foramanufacturers thermalefficiency ratingof0.90 (based on the LHV), the nominal thermal efficiency entered here is 0.82 (i.e. 0.9multiplied by45,450/50,000).

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2.4.6 82BDesignCondition

Figure29:Hotwaterboilerdialogshowingdesignconditionsubtab

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Thedesignconditiondata intheDesignConditionsubtab (asdescribedbelow)willbeareadonly (uneditable)copyofthecurrentratedconditiondatawhenthe Ratedcondition isDesignconditionbox isticked,includinganyunsavededitsyouhavemadeintheRatedConditionsubtab.

2.4.6.1 HotWaterSupplyTemperature,Tlbtdes

Enterthedesignhotwatersupplytemperature(leavingboilerwatertemperature).

2.4.6.2 HotWaterFlowRate,Vbdes,Vbdes/Qdes,Tbdes

Enter the design hot water flow rate. Vbdes, Vbdes/Qdes, and Tbdes are three different options forspecifyingdesignhotwaterflowrate.CurrentlyitisspecifiedintermsofTbdes(thedifferencebetweenthedesignhotwatersupplyandreturntemperatures).Theothertwooptions(VbdesandVbdes/Qdes(theratiobetweendesignhotwater flow rate (Vbdes)anddesignheatingcapacity (Qdes).)areautomaticallyderivedbytheprogrambasedonthespecifiedTbdesandcannotbeedited.

Note:IfthereisanairsourceheatpumporCH(C)Pplantattachedtotheboilerloop,youshouldcalculatewhatproportionofthetotalloadtheboilertakesatthepeakcondition(whichishardforthesoftwaretodetermine automatically) and reduce Tbdes by this factor. (In general, Tbdes is the temperature riseacrosstheboiler,notthewaterloop.)

2.4.6.3 HeatingCapacity,Qdes

Thedesignheatingcapacityisalwaysacopyofheatingcapacityatratedconditionanddoesnotneedtobeedited.

2.4.6.4 Boilerefficiency,Edes

The boiler design efficiency is automatically derived by the program using other design and ratedconditiondataprovidedanddoesnotneedtobeedited.

2.4.7 83BOperatingParameters

2.4.7.1 HotWaterSupplyTemperatureSetPointType

Threeoptionsareavailableforhotwatersupplytemperaturesetpointtype:Constant,Timed,orReset.

2.4.7.2 ConstantHotWaterSupplyTemperatureSetPoint

WhenConstantisselectedforhotwatersupplytemperaturesetpointtype,thisfieldisautomaticallysetbytheprogramasthehotwatersupplytemperatureatdesigncondition,whichhasbeenenteredintheDesignconditionsubtab.

2.4.7.3 TimedHotWaterSupplyTemperatureSetPointProfile

WhenTimedisselectedforhotwatersupplytemperaturesetpointtype,selecttheabsoluteprofiletobeappliedtothehotwatersupplytemperaturesetpoint,whicharedefinedthroughtheAPProfacility(theProfilesDatabase).

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Figure210:Hotwaterboilerdialogshowingoperatingparameterssubtab

2.4.7.4 HotWaterSupplyTemperatureResetType

WhenReset is selected forhotwater supply temperature setpoint type, select thehotwater supplytemperatureresettype.Currentlyonlyoneoption isprovided:Outdoorairtemperaturereset.When

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Outdoorairtemperatureresettypeisselected,whichisthedefault,youalsoneedtospecifythreemoreresetparameters:

Outdoordrybulbtemperaturelowlimit Outdoordrybulbtemperaturehighlimit Hotwatersupplytemperatureatorabovehighlimit

The fourth parameter (Hotwater supply temperature at or below low limit) required byOutdoor airtemperature reset type is automatically set by the program as the hotwater supply temperature atdesigncondition.

2.4.7.5 OutdoorDrybulbTemperatureLowLimit

Whenhotwatersupplytemperatureresettype isselectedasOutdoorairtemperaturereset,entertheoutdoordrybulbtemperaturelowlimittobeusedbythereset.

2.4.7.6 HotWaterSupplyTemperatureatorbelowLowLimit

When hot water supply temperature reset type is selected as Outdoor air temperature reset, thisparameter isautomaticallysetbytheprogramasthehotwatersupplytemperatureatdesignconditionanddoesnotneedtobespecified.

2.4.7.7 OutdoorDryBulbTemperatureHighLimit

Whenhotwatersupplytemperatureresettype isselectedasOutdoorairtemperaturereset,entertheoutdoordrybulbtemperaturehighlimittobeusedbythereset.

2.4.7.8 HotWaterSupplyTemperatureatoraboveHighLimit

Whenhotwatersupplytemperatureresettype isselectedasOutdoorairtemperaturereset,enterthehotwatersupplytemperatureatorabovetheoutdoordrybulbtemperaturehighlimittobeusedbythereset.

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2.4.8 84BPumps

Figure211:Hotwaterboilerdialogshowinghotwaterpumpstab

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2.4.8.1 HotWaterPumpSpecificPower

Enter thehotwaterpump specificpower,expressed inW/(l/s) inSIunits (orW/gpm in IPunits).Thedefaultvalue(19W/gpm) isbasedonthedesignhotwaterpumpspecificpowerasspecified inASHRAE90.1G3.1.3.5.

Hotwaterpumppowerwillbecalculatedonthebasisofvariableflow,withhotwatercircuitflowratevaryinginproportiontothecircuitheatingload(assignedbytheheatingcoils,hotwaterradiators,etc.).

Thedesignhotwater circuit flow rate is calculatedusing theboilerdesignheating capacity (Qdes), theboilerdesignhotwatertemperaturechange,Tbdesandtheinformationonboilerconfiguration(whether2identicalstagedboilersoperatinginparallel?isselected).

Thedesignhotwaterpumppoweriscalculatedasthespecificpumppowermultipliedbythedesignhotwatercircuitflowrate.Itisthenmodifiedbythepumppowercurvetogettheoperatingpumppower.

2.4.9 85BPumpheatgaintohotwaterloop(fraction)Enterthehotwaterpumpmotorefficiencyfactor,whichisthefractionofthemotorpowerthatendsupin thehotwater. Itsvalue ismultipliedby thehotwaterpumppower toget thehotwaterpumpheatgain,whichisdeductedfromtheheatingloadoftheboiler.

2.4.9.1 HotWaterPumpPerformanceCurve,fPv(v)

The hotwaterpump power curve currently selected.Use the Selectbutton to select the appropriatecurve from thesystemdatabase.Use theEditbutton toedit thecurveparameters ifyou like.TheEditbuttonwill pop up a dialog displaying the formula and parameters of the curve, allowing the curveparameters tobe edited. You are allowed to edit the curve coefficients, in addition to the applicablerangesofthecurve independentvariables.Wheneditingthecurveparameters, it is importantthatyouunderstandthemeaningofthecurveanditsusageinthemodelalgorithm.

Alsobecarefulthattheeditedcurvehasreasonableapplicablerangesforthe independentvariables.Aperformancecurveisonlyvalidwithinitsapplicableranges.Inthecasetheindependentvariablesareoutoftheapplicablerangesyouset,thevariablelimits(maximumorminimum)youspecifiedintheinputwillbeapplied.

ThehotwaterpumppowercurvefPv(v)isacubicfunctionof

v=V/Ve

where

V=pumpvolumetricflowrate.

Ve=designpumpvolumetricflowrate.

And:

fPv(v)=(C0+C1v+C2v2+C3v

3)/Cnorm

where

C0,C1,C2andC3arethecurvecoefficients

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Cnormisadjusted(bytheprogram)tomakefPv(1)=1

Thehotwaterpumppowercurveisevaluatedforeachtimestepduringthesimulation.Thecurvevalueismultipliedby thedesignhotwaterpumppower toget theoperatingpumppowerof thecurrent timestep,forthecurrentfractionofpumpvolumetricflowrate.

Thecurveshouldhaveavalueof1.0whenthepumpvolumetricflowrateequalsdesignpumpvolumetricflowrate(v=1.0).

Figure212:Selectdialogforthehotwaterpumppowercurve

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Figure213:Editdialogforthehotwaterpumppowercurve

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2.5 Airsourceheatpump

Theairsourceheatpump(ASHP)canbetheprimaryheatsourceforanyheatingcoilorradiator.

The AHSP component is placed on the airside network. As its capacity will vary with the sourcetemperature,abackupheatsourcemust firstbedefined (see 209HFigure22)andthenassignedwithin theASHPdialog.WhileavailableASHPcapacitywillbeusedfirst,coilsandradiatorsareassignedtothehotwaterboilersorpartloadcurveheatsourcethathasbeensetasthebackup.

Toolbariconforplacementofaheatpump.

Heatpumpcomponent.

Theheatpumpshouldbeplacedattheappropriatelocationinthenetwork(typicallythefreshairinlet)todeterminethetemperatureoftheheatsource.Notethattheairsourceheatpumpdoesnotinfluencethetemperatureofairatthenodetowhich it isconnectedi.e.,an infinitesourceofvaryingtemperature,suchas theoutdoorenvironment, isassumed.Thesource temperaturedetermines thevariationof theCOPandthemaximumoutputofthedeviceatanygivensimulationtimestep.

Figure214:Airsourceheatpumpdialogwith illustrative inputsprovidedbydefaultfortheASHP inthepredefinedpackagedsinglezoneheatpump(04PSZHP)system.

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Figure215:AirsourceheatpumpperformanceassociatedwithillustrativeinputsinFig.214

Figure216:GraphicrepresentationoftheillustrativeinputsinFig.214

Figures214,15,and16aboveshowillustrativeinputsfortheASHPdialogandtherelationshipbetweentheseandtheToincludeboththechangeinperformancewithoutdoortemperatureandthereducedCOPatpart load,simulationresultswereusedtodeterminethatthe loadplacedupontheASHPaftersizingwouldbe100%at32F,withsupplementalheatfromthebackupheatsourceincreasinglyrequiredbelowthattemperatureand,above32F,heatingloadgraduallydiminishingto40%atanoutdoortemperatureof62F.ThisinformationwasusedtodeterminethepartloadCOPcurve(dashedline)inFigure215.Tofacilitateinsertionoftheautosizedcapacity(baseduponthewinterheatingdesigndayconditionsfortheproject location) in the row associatedwith the ARI testing condition (47 F) used to determine theequipmentcapacityandCOP,thecurvesareintentionallytruncatedtoendat47F.

TheinputsintheASHPdialogcouldbeextendedtowarmertemperaturesifneeded.Becausethedialogaccepts just10 rowsofdata, the spacingbetweendatapointswouldneed tobe somehowaltered toaccommodatethis.Becausethemodeluses linear interpolationbetween thedatapointsprovided,andtheCOPandcapacitycurvesarebothrelativelyflatbetweenabout17and32F,thiswouldbethebestregionofthecurvetoberepresentedbyareduceddensityofdatapoints.

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2.5.1 86BHeatpumpsettings

2.5.1.1 Reference

Enteradescriptionofthecomponent.Thereferenceislimitedto100characters.Itisforyourusewhenselecting, organizing, and referencing any component or controllers within other component andcontrollerdialogsandinthecomponentbrowsertree.Thesereferencescanbevaluableinorganizingandnavigating thesystemandwhen thesystemmodel is later reusedonanotherprojectorpassedon toanothermodeler. Reference names should thus be informativewith respect to differentiating similarequipment,components,andcontrollers.

2.5.1.2 Backupheatsource

Abackupheatsourcemustfirstbedefined(see 210HFigure22)andthenassignedhere.Itisgoodpracticetoincludeaheatpumpdesignation,suchasASHP01+HWboilerbackupinthenameofthebackupheatsource, as this iswhat youwill select in the heating coil or radiator dialog in order to connect to aparticularASHP.Notethatthroughversion6.3,theASHPcapacitywillbeusedfirst,andonlythenwilltheremaining loadbemetbyanyrecoveredcondenserheatfromachillerorCHPresourceassociatedwiththebackupheatsource (thismaychange inversion6.4 inorder tosupportmodelingofVRVsystemswhereinthecoolingandheatingfunctionsinmultiplezonesshareacommoncondenserloop).

2.5.1.3 MinimumSourceTemperature

Theheatpumpisassumedtoswitchoffcompletelywhenthesourcetemperaturedropsbelowthisvalue.Abovethisvalue,theheatpumpisassumedtomeetasmuchoftheloadasitcan,withtheheatsourcebeingbroughtintotopupthisdemandifrequired.

2.5.2 87BHeatpumpperformance

2.5.2.1 SourceTemperature

This line of information describes the variation in the performance of the heat pump as the sourcetemperaturevaries.Enterthesourcetemperature.Uptotenpointsmaybeusedtodefinethevariationofperformancewithsourcetemperature.Enterthepointsinascendingorderofsourcetemperature.

2.5.2.2 HeatPumpCOP

Enter the coefficientofperformanceof theheatpumpat the corresponding source temperature.Thisvalue is the useful heat output divided by the total fuel energy consumption associated with theoperationofthisdevice(excludingelectricalconsumptionofanydistributionpumps included inheatingplantcomponents).

2.5.2.3 Output

Enterthemaximumheatpumpoutputatthecorrespondingsourcetemperature.Ifthedemandforheatoutputexceedsthisvaluethentheheatsourceisusedtomakeuptheextrademand.

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2.6 17BChilledWaterLoops,HeatRejection,andChillerSequencing

Thechilledwater looptoolprovidesaccesstoselection,editing,andaddingorremovingnamedchilledwaterloops.Eachindividualchilledwaterloopdialogthenprovidesinputsfortofollowing:

primaryandsecondarychilledwaterloopsandoptiontousejustoneofthese chillers and other similar cooling sources (adding, sequencing, and editing of cooling

equipmentontheprimarychilledwaterloop)

heatrejection loop (forwatercooled chillers)with cooling towerandoptions forwatersideeconomizerandcondenserheatrecovery

Achilledwater loop isassociatedwithachillersetcomprisinganynumberofchillers,whichcan includeanycombinationofthreedifferenttypes:

electricwatercooledchiller(useseditablepredefinedcurvesandotherstandardinputs) electricaircooledchiller(useseditablepredefinedcurvesandotherstandardinputs) partloadcurvechiller(flexiblegenericinputs;canrepresentanydeviceusedtocoolwatervia

amatrixofloaddependentdataforCOPandassociatedusageofpumps,heatrejectionfans,etc.,withtheoptionofaddingCOPvaluesforuptofouroutdoorDBTorWBTconditions)

Eachchillerorsimilarpieceofwatercoolingequipmentisdefinedinthecontextofachilledwaterloop.Thusnochillerispermittedtoservemorethanoneprimarychilledwaterloop.ChillerscanbeduplicatedusingtheCopybuttonwithinachillersetandanImportfacilityisprovidedforcopyingadefinedchillerfromonechilledwaterlooptoanother.

An optional condenserwater loop is associatedwith each primary chilledwater loop. This includes acooling towermodeland is requiredonlywhen thechillerset includesanelectricwatercooledchiller.Aircooledchillersuseonlythedesigntemperatures(DBTandWBT)forheatrejection.Heatrejectionforthe genericpartloadcurve chiller type isdescribedby theuser via any combinationofCOP values,pumppower,andfanpower(alloranyofwhichcanbeincludedinacompositeCOP)inthedialogforthattypeofequipment.

Coolingcoilsandchilledceilingsareassignedachilledwaterloopratherthanachiller.Whilethestandardconfigurationusesaprimaryplussecondary loopconfiguration, theprimary loopcanbeeliminatedbyzeroingoutitspumppowersuchthatthesystemismodeledasaprimaryonlyconfigurationusingthesecondaryloop.

During simulation, chillerswithin a chiller set are switched in according to a userspecified sequence.Duringautosizing, sequenced chillersand theassociatedheat rejectionplantandwater flow ratesaresized on the basis of userspecified percentages of the peak design load.When electricwatercooledchillers are included, and thus there is an associated cooling tower, the chiller set may operate inwatersideeconomizermode.

Thechilledwaterloopcomponentisaccessedthroughthetoolbariconshownbelow.

ToolbariconforChilledwaterloops.

ClickingthistoolbariconopensuptheChilledwaterloopsdialog(showninFigure217),whichmanagesasetofchilledwater loops.Achilledwater loopmaybeadded,edited,removedorcopiedthroughthecorrespondingbuttonsinthisdialog.Doubleclickingonanexistingchilledwaterloop(orclickingtheEdit

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buttonafterselectionofanexistingchilledwaterloop)opensuptheChilledwaterloopdialog(showninFigure218),wherechilledwaterloopparametersmaybeedited.

TheChilledwaterloopdialogcurrentlyhasthreetabs:

Chilledwaterlooptab:Thistabmanagesthepropertiesofthechilledwaterloop. Heat rejection tab: This tab manages information used for heat rejection. An optional

condenserwater loop for use by electricwatercooled chillers and (optionally) awatersideeconomizercanbedefinedinthistab.

Chillersettab:Thistabmanagesalistofchillers(achillerset),whichmaybeeditedwithchillerdialogs(seesection2.5,2.6and2.7).Chillersequencingranksundervariablepartloadrangesarealsodefinedinthistab,togetherwithchillerautosizingcapacityweightings.

Currentlyifacondenserwaterloophasbeendefinedforachilledwaterloop,atleastoneelectricwatercooled chiller must also be defined for the same chilled water loop. Electric watercooled chillersbelongingtothesamechillersetshareacommoncondenserwater loopandcoolingtower.ThecoolingtowermodelusedisthesameasthatusedfortheWaterSideEconomizermodel,whichisbasedontheMerkeltheory.

Forthecondenserwaterloop,acondenserwaterpumpisassumedtobeonthesupplysideofthecoolingtower.

Whencondenserwaterflowrateisdifferentfromtheratedcondenserwaterflowrate,anadjustmentismade to the entering condenser water temperature used by the program to solve for the chillerperformanceintheiterationprocess.Theadjustmentismadebasedonthefollowingprinciple:

Settheeffectiveenteringcondenserwatertemperaturetothevaluewhich,forthegivenrateofheatrejection,wouldproducethesamecondenserwater leavingtemperatureasachilleroperatingwiththeratedcondenserwaterflowrate.

Thechilledwater loopconfiguration isassumedtobeaprimary/secondarysystem,servedbyaprimarycircuitchilledwaterpumpandasecondarycircuitchilledwaterpump.

Bothcondenserwaterpumpandprimarycircuitchilledwaterpumpareassumedtooperateinlinewiththechiller.Thecondenserwaterflowrateandprimarycircuitchilledwaterflowrateareassumedtobeconstant (atthedesignvalues)whenthechiller ison.Theyaremultipliedbythecorrespondingspecificpump power to get the condenser water pump power and the primary chilled water pump powerrespectively.

The secondary circuit chilledwaterpump isassumed tooperate in linewith the chiller, subject to theconstraintthatthepumpwillstartcyclingbelowtheminimumflowrateitpermits.Requiredchilledwaterflowratesforsimplecoolingcoilsandchilledceilingsvary inproportiontotheircooling loads.Requiredchilledwaterflowrateforadvancedcoolingcoilsaredeterminedbythedetailedheattransfercalculationof theadvancedcoolingcoilmodel.Requiredchilledwater flow rates fromallcoolingcoilsandchilledceilings servedbyachilledwater loopare summed toget the required secondarycircuit chilledwaterflowrate,subjecttotheminimumpumpflowratethepumppermits.Thedesignsecondarychilledwaterpump power is calculated as the secondary specific pump powermultiplied by the design secondarychilledwaterflowrate(assumedequaltodesignprimarychilledwaterflowrate).It isthenmodifiedbythesecondarycircuitpumppowercurvetogettheoperatingsecondarypumppower.

Distributionlossesfromthepipeworkareconsideredasauserspecifiedpercentageofthechilledwaterloopload.Inaddition,chilledwaterandcondenserwaterpumpheatgainsaremodeledbypumpmotorefficiencyfactors.

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Condenserheat recovery is included in thecurrentmodelasa simpleuserspecifiedpercentageof thethermalenergyrejectedtothecondenserloop.Thispercentagerepresentsheatexchangereffectiveness.Theavailablecondenserheatisthenassignedtoareceivingheatsourcethatwillusethisrecoveredheatfirstwhen a load is present. The user has the options to upgrade the hotwater temperature for therecoveredheatonthereceiving (HW loop)endwithanelectricwatertowaterheatpumpforusewithtypicalspaceheatingloads.