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DHWLOOPHEATER

DHWHEATERLOOP constructs an object representing a hot water heater dedicated to heating DHWLOOP return water (or several if identical).

whName

Optional name of water heater; give after the word “DHWHEATER” if desired.

Units Legal Range Default Required Variability
63 characters none No constant

whMult

Type: integer

Number of identical water heaters of this type. Any value \(>1\) is equivalent to repeated entry of the same DHWHEATER.

Units Legal Range Default Required Variability
x \(>\) 0 1 No constant

whType

Type: choice

Type of water heater. This categorization is based on CEC and federal rating standards that change from time to time.

SMALLSTORAGE A storage water heater having an energy factor (EF) rating. Generally, a gas-fired storage water heater with input of 75,000 Btuh or less, an oil-fired storage water heater with input of 105,000 Btuh or less, an electric storage water heater with input of 12 kW or less, or a heat pump water heater rated at 24 amps or less.
LARGESTORAGE Any storage water heater that is not SMALLSTORAGE.
SMALLINSTANTANEOUS A water heater that has an input rating of at least 4,000 Btuh per gallon of stored water. Small instantaneous water heaters include: gas instantaneous water heaters with an input of 200,000 Btu per hour or less, oil instantaneous water heaters with an input of 210,000 Btu per hour or less, and electric instantaneous water heaters with an input of 12 kW or less.
LARGEINSTANTANEOUS An instantaneous water heater that does not conform to the definition of SMALLINSTANTANEOUS, an indirect fuel-fired water heater, or a hot water supply boiler.
INSTANTANEOUSUEF An instantaneous water heater having a UEF rating (as opposed to EF).
Units Legal Range Default Required Variability
Codes listed above SMALLSTORAGE No constant

whHeatSrc

Type: choice

Heat source for water heater. CSE implements uses efficiency-based models for all whTypes (as documented in RACM, App. B). In addition, the detailed Ecotope HPWH model is available for electric (air source heat pump and resistance) SMALLSTORAGE water heaters.

RESISTANCE Electric resistance heating element Deprecated for whType=SMALLSTORAGE (use RESISTANCEX)
RESISTANCEX Electric resistance heating element, detailed HPWH model
ASHP Air source heat pump, EF model Deprecated for whType=SMALLSTORAGE (use ASHPX)
ASHPX Air source heat pump, detailed HPWH model
FUEL Fuel-fired burner
Units Legal Range Default Required Variability
Codes listed above FUEL No constant

whResType

Type: choice

Resistance heater type, valid only if whHeatSrc is equal to RESISTANCEX, else ignored. These choices are supported by the detailed HPWH model. Except for Generic, all heater characteristics are set by HPWH based on whResType.

Units Legal Range Default Required Variability
Typical
SwingTank Typical No constant

whHeatingCap

Type: float

Nominal heating capacity, available only for a limited HPWH types.

Units Legal Range Default Required Variability
Btuh x \(>\) 0 0 No constant

whVol

Type: float

Storage tank volume. Must be omitted or 0 for instantaneous whTypes. Used by HPWH model (whHeatSrc=RESISTANCEX or whHeatSrc=ASHPX). Required when whHeatSrc=RESISTANCEX or whHeatSrc=ASHPX with whASHPType=GENERIC. For all other configurations, whVol is documentation-only.

Units Legal Range Default Required Variability
gal \(\ge\) 0.1 (caution: small values may cause runtime errors) per whASHPType if HPWH else 50 For some HPWH configurations, see above constant

whVolRunning

Type: float

Running storage volume is the volume above aquastat. Requires the total volume based on aquastat position. Ecotope's HPWH tank and heater.

Units Legal Range Default Required Variability
gal x \(>\) 0 0 No constant

whEF

Type: float

Rated energy factor that specifies DHWHEATER efficiency under test conditions. Used by CSE to derive annual water heating efficiency and/or other characteristics as described below. Calculation methods are documented in RACM, Appendix B.

Configuration whEF default Use
whType=SMALLSTORAGE, whHeatSrc=RESISTANCE or FUEL 0.82 Derivation of whLDEF
whType=SMALLSTORAGE, whHeatSrc=ASHP 0.82 Derivation of whLDEFnote inappropriate default (deprecated, use ASHPX)
whType=SMALLSTORAGE, whHeatSrc=ASHPX, whASHPType=GENERIC (req'd) Tank losses Overall efficiency
whType=SMALLSTORAGE, whHeatSrc=RESISTANCEX (req'd) Tank losses Note: maximum whEF=0.98.
whType=SMALLINSTANTANEOUS, whHeatSrc=RESISTANCE or FUEL 0.82 Annual efficiency = whEF*0.92
Any other (unused)
Units Legal Range Default Required Variability
\(>\) 0 Caution: maximum not checked. Unrealistic values will cause runtime errors and/or invalid results See above See above constant

whLDEF

Type: float

Load-dependent energy factor for DHWHEATERs with whType=SMALLSTORAGE and whHeatSrc=FUEL or whHeatSrc=RESISTANCE. If not given, whLDEF is derived using a preliminary simulation activated via DHWSYS wsCalcMode=PRERUN. See RACM Appendix B.

Units Legal Range Default Required Variability
x \(>\) 0 Calculated via DHWSYS PreRun mechanism When whType = SMALLSTORAGE and PreRun not used constant

whUEF

Type: float

Water heater Uniform Energy Factor efficiency rating, used when whType=INSTANTANEOUSUEF.

Units Legal Range Default Required Variability
x \(\ge\) 0 none when whType= INSTANTANEOUSUEF constant

whAnnualElec

Type: float

Annual electricity use assumed in UEF rating derivation. Used when whType=INSTANTANEOUSUEF.

Units Legal Range Default Required Variability
kWh x \(\ge\) 0 none when whType= INSTANTANEOUSUEF constant

whAnnualFuel

Type: float

Annual fuel use assumd in UEF rating derivation, used when whType=INSTANTANEOUSUEF.

Units Legal Range Default Required Variability
therms x \(\ge\) 0 none when whType= INSTANTANEOUSUEF constant

whRatedFlow

Type: float

Maximum flow rate assumed in UEF rating derivation. Used when whType=INSTANTANEOUSUEF.

Units Legal Range Default Required Variability
gpm x \(>\) 0 none when whType= INSTANTANEOUSUEF constant

whStbyElec

Type: float

Instantaneous water heater standby power (electricity consumed when heater is not operating). Used when whType=INSTANTANEOUSUEF.

Units Legal Range Default Required Variability
W x \(\ge\) 0 4 No constant

whLoadCFwdF

Type: float

Instanteous water heater load carry forward factor -- approximate number of hours the heater is allowed to meet water heating demand that is unmet on a 1 minute basis, used when whType=INSTANTANEOUSUEF.

Units Legal Range Default Required Variability
x \(\ge\) 0 1 No constant

whZone

Type: znName

Name of zone where water heater is located, used only in detailed HPWH models (whHeatSrc=ASHPX or whHeatSrc=RESISTANCEX), otherwise no effect. Zone conditions are used for tank heat loss calculations. Heat losses from the DHWHEATER are included in the zone heat balance. whZone also provides the default for whASHPSrcZn (see below).

whZone and whTEx cannot both be specified.

Units Legal Range Default Required Variability
name of a ZONE Not in a zone (heat losses discarded) No constant

whTEx

Type: float

Water heater surround temperature, used only in detailed HPWH models (whHeatSrc=ASHPX or whHeatSrc=RESISTANCEX), otherwise no effect. When whTEx is specified, tank heat losses are calculated using whTEx and modify tank water temperatures, but the lost heat has no external effect.

whZone and whTEx cannot both be specified.

Units Legal Range Default Required Variability
oF x \(\ge\) 0 whZone air temperature if specified, else 70 oF No hourly

whASHPType

Type: choice

Air source heat pump type, valid only if whHeatSrc=ASHPX. These choices are supported by the detailed HPWH model. Except for Generic, all heater characteristics are set by HPWH based on whASHPType.

Choice Specified type
Generic General generic (parameterized by wh_EF and wh_vol)
AOSmithPHPT60 60 gallon Voltex
AOSmithPHPT80 80 gallon Voltex
AOSmithHPTU50 50 gallon AOSmith HPTU
AOSmithHPTU66 66 gallon AOSmith HPTU
AOSmithHPTU80 80 gallon AOSmith HPTU
AOSmithHPTU80DR 80 gallon AOSmith HPTU (demand reduction variant)
AOSmithCAHP120 120 gallon AOSmith
Sanden40 Sanden 40 gallon CO2 external heat pump
Sanden80 Sanden 80 gallon CO2 external heat pump
Sanden120 Sanden 120 gallon CO2 external heat pump
SandenGS3 Sanden GS3 compressor CO2 external
GE2012 2012 era GeoSpring
GE2014 2014 80 gal GE model run in the efficiency mode
GE2014_80DR 2014 80 gal GE model run in the efficiency mode (demand reduction variant)
GE2014StdMode 2014 50 gal GE run in standard mode
GE2014StdMode80 2014 80 gal GE run in standard mode
RheemHB50 newish Rheem (2014 model?)
RheemHBDR2250 50 gallon 2250 W resistance Rheem HB Duct Ready
RheemHBDR4550 50 gallon 4500 W resistance Rheem HB Duct Ready
RheemHBDR2265 65 gallon 2250 W resistance Rheem HB Duct Ready
RheemHBDR4565 65 gallon 4500 W resistance Rheem HB Duct Ready
RheemHBDR2280 80 gallon 2250 W resistance Rheem HB Duct Ready
RheemHBDR4580 80 gallon 4500 W resistance Rheem HB Duct Ready
Rheem2020Prem40 40 gallon Rheem 2020 Premium
Rheem2020Prem50 50 gallon Rheem 2020 Premium
Rheem2020Prem65 65 gallon Rheem 2020 Premium
Rheem2020Prem80 80 gallon Rheem 2020 Premium
Rheem2020Build40 40 gallon Rheem 2020 Builder
Rheem2020Build50 50 gallon Rheem 2020 Builder
Rheem2020Build65 65 gallon Rheem 2020 Builder
Rheem2020Build80 80 gallon Rheem 2020 Builder
RheemPlugInShared40 40 gal Rheem plug-in 120V shared circuit (no resistance elements)
RheemPlugInShared50 50 gal Rheem plug-in 120V shared circuit (no resistance elements)
RheemPlugInShared65 65 gal Rheem plug-in 120V shared circuit (no resistance elements)
RheemPlugInShared80 80 gal Rheem plug-in 120V shared circuit (no resistance elements)
RheemPlugInDedicated40 40 gal Rheem plug-in 120V dedicated circuit (no resistance elements)
RheemPlugInDedicated50 50 gal Rheem plug-in 120V dedicated circuit (no resistance elements)
Stiebel220E Stiebel Eltron (2014 model?)
AOSmithSHPT50 AOSmith add'l models (added 3-24-2017)
AOSmithSHPT66 AOSmith add'l models (added 3-24-2017)
AOSmithSHPT80 AOSmith add'l models (added 3-24-2017)
GenericTier1 Generic Tier 1
GenericTier2 Generic Tier 2
GenericTier3 Generic Tier 3
Generic General generic (parameterized by EF and vol)
UEF2Generic Experimental UEF=2
WorstCaseMedium UEF2Generic alias (supports pre-existing test cases)
BasicIntegrated Typical integrated HPWH
ResTank Resistance heater (no compressor). Superceded by whHeatSrc=RESITANCEX
ResTankNoUA Resistance heater (no compressor) with no tank losses. Superseded by whHeatSrc=RESISTANCEX.
AOSmithHPTU80DR 80 gallon AOSmith HPTU with fixed backup setpoint (experimental for demand response testing)
AOSmithSHPT50 50 gal AOSmith SHPT
AOSmithSHPT66 66 gal AOSmith SHPT
AOSmithSHPT80 80 gal AOSmith SHPT
AOSmithHPTS40 40 gal AOSmith HPTS
AOSmithHPTS50 50 gal AOSmith HPTS
AOSmithHPTS66 66 gal AOSmith HPTS
AOSmithHPTS80 80 gal AOSmith HPTS
ColmacCxV5_SP Colmac CxA-xx modular external HPWHs (single pass mode)
ColmacCxA10_SP Colmac CxA-xx modular external HPWHs (single pass mode)
ColmacCxA15_SP Colmac CxA-xx modular external HPWHs (single pass mode)
ColmacCxA20_SP Colmac CxA-xx modular external HPWHs (single pass mode)
ColmacCxA25_SP Colmac CxA-xx modular external HPWHs (single pass mode)
ColmacCxA30_SP Colmac CxA-xx modular external HPWHs (single pass mode)
ColmacCxV5_MP Colmac CxA-xx modular external HPWHs (multi-pass mode)
ColmacCxA10_MP Colmac CxA-xx modular external HPWHs (multi-pass mode)
ColmacCxA15_MP Colmac CxA-xx modular external HPWHs (multi-pass mode)
ColmacCxA20_MP Colmac CxA-xx modular external HPWHs (multi-pass mode)
ColmacCxA25_MP Colmac CxA-xx modular external HPWHs (multi-pass mode)
ColmacCxA30_MP Colmac CxA-xx modular external HPWHs (multi-pass mode)
NyleC25A_SP Nyle Cxx external HPWHs (SP = single pass mode)
NyleC60A_SP Nyle Cxx external HPWHs (SP = single pass mode)
NyleC90A_SP Nyle Cxx external HPWHs (SP = single pass mode)
NyleC125A_SP Nyle Cxx external HPWHs (SP = single pass mode)
NyleC185A_SP Nyle Cxx external HPWHs (SP = single pass mode)
NyleC250A_SP Nyle Cxx external HPWHs (SP = single pass mode)
NyleC60A_CWP_SP Nyle Cxx external SP HPWHs with cold weather package
NyleC90A_CWP_SP Nyle Cxx external SP HPWHs with cold weather package
NyleC125A_CWP_SP Nyle Cxx external SP HPWHs with cold weather package
NyleC185A_CWP_SP Nyle Cxx external SP HPWHs with cold weather package
NyleC250A_CWP_SP Nyle Cxx external SP HPWHs with cold weather package
NyleC60A_MP Nyle Cxx external HPWHs (MP = multi-pass mode)
NyleC90A_MP Nyle Cxx external HPWHs (MP = multi-pass mode)
NyleC125A_MP Nyle Cxx external HPWHs (MP = multi-pass mode)
NyleC185A_MP Nyle Cxx external HPWHs (MP = multi-pass mode)
NyleC250A_MP Nyle Cxx external HPWHs (MP = multi-pass mode)
NyleC60A_CWP_MP Nyle Cxx external MP HPWHs w/ cold weather package
NyleC90A_CWP_MP Nyle Cxx external MP HPWHs w/ cold weather package
NyleC125A_CWP_MP Nyle Cxx external MP HPWHs w/ cold weather package
NyleC185A_CWP_MP Nyle Cxx external MP HPWHs w/ cold weather package
NyleC250A_CWP_MP Nyle Cxx external MP HPWHs w/ cold weather package
Rheem_HPHD60HNU_MP Rheem HPHD60 MP external MP HPWHs
Rheem_HPHD60VNU_MP Rheem HPHD60 MP external MP HPWHs
Rheem_HPHD135HNU_MP Rheem HPHD135 MP external MP HPWHs
Rheem_HPHD135VNU_MP Rheem HPHD135 MP external MP HPWHs
Scalable_SP single pass scalable type for autosized standard design
Scalable_MP multipass scalable type for autosized standard design
AquaThermAire Villara AquaThermAire HPWH
GenericUEF217 65-gal tank meeting Federal standard minimum requirement
AWHSTier4Generic40 Any 40-gal tank meeting Advanced Water Heating Specification Tier-4 minimum requirements
AWHSTier4Generic50 Any 50-gal tank meeting Advanced Water Heating Specification Tier-4 minimum requirements
AWHSTier4Generic65 Any 65-gal tank meeting Advanced Water Heating Specification Tier-4 minimum requirements
AWHSTier4Generic80 Any 80-gal tank meeting Advanced Water Heating Specification Tier-4 minimum requirements
BradfordWhiteAeroThermRE2H50 Bradford White 50-gal AeroTherm2023
BradfordWhiteAeroThermRE2H65 Bradford White 65-gal AeroTherm2023
BradfordWhiteAeroThermRE2H80 Bradford White 80-gal AeroTherm2023
LG_APHWC50 LG 50-gal integrated HPWH
LG_APHWC80 LG 580-gal integrated HPWH
Units Legal Range Default Required Variability
Codes listed above none When whHeatSrc=ASHPX constant

whASHPSrcZn

Type: znName

Name of zone that serves as heat pump heat source used when whHeatSrc=ASHPX. Heat removed from the zone is added to the heated water and is included in zone heat balance (that is, heat pump operation cools the zone).

whASHPSrcZn and whASHPSrcT cannot both be specified.

Units Legal Range Default Required Variability
name of a ZONE whZoneIf no zone is specified by input or default, heat extracted by ASHP has no effect. No constant

whASHPSrcT

Type: float

Heat pump source air temperature used when whHeatSrc=ASHPX. Heat removed from this source is added to the heated water but has no other effect.

whASHPSrcZn and whASHPSrcT cannot both be specified.

The logic to determine the temperature of the heat pump source air is:

        if whASHPSrcT is specified
          use whASHPSrcT
        else if whASHPSRCZn is specified
          use whASHPSrcZn air temp
        else if whZone is specified
          use whZone air temp
        else
          use 70 F

To model a heat pump that uses outdoor air as its heat source, omit whASHPSrcZn and specify whASHPSrcT = $tDbO.

Units Legal Range Default Required Variability
oF x \(\ge\) 0 70 oF (used only when whASHPSrcZn and whZone not specified) No hourly

whASHPResUse

Type: float

Specifies activation temperature difference for resistance heating, used only when whHeatSrc=ASHPX and whASHPType=GENERIC. Refer to HPWH engineering documentation for model details.

Units Legal Range Default Required Variability
oC x \(\ge\) 0 7.22 No constant

whResHtPwr

Type: float

Specifies resistance upper element power, used only with whHeatSrc=RESISTANCEX.

Units Legal Range Default Required Variability
W x \(\ge\) 0 4500 No constant

whResHtPwr2

Type: float

Specifies resistance lower element power, used only with whHeatSrc=RESISTANCEX.

Units Legal Range Default Required Variability
W x \(\ge\) 0 whResHtPwr No constant

whUA

Type: float

HPWH-type total UA (not per tank)

Units Legal Range Default Required Variability
Btuh/F x \(\geq\) 0 HPWH default No constant

whInsulR

Type: float

Tank insulation resistance for heat pump water heater.

Units Legal Range Default Required Variability
hr-F/Btuh x \(>\) 0 -1 No constant

whInHtSupply=float\

whInHtLoopRet

Type: float

Fractional tank height of inlets for supply water and DHWLOOP return, used only with HPWH types (whHeatSrc=RESISTANCEX or whHeatSrc=ASHPX). 0 indicates the bottom of the water heater tank and 1 specifies the top. Inlet height influences tank layer mixing and can impact heat pump COP and/or heating activation frequency.

Units Legal Range Default Required Variability
0 \(\le\) x \(\le\) 1 HPWH default (0?) No constant

whtankCount

Type: float

Number of storage tanks per DHWHEATER, re built-up whType=Builtup, does not reflect wh_mult (wh_mult=2, wh_tankCount=3 -> 6 tanks).

Units Legal Range Default Required Variability
# x \(\geq\) 1 1 No constant

whEff

Type: float

Water heating efficiency, used in modeling whType=LARGESTORAGE and whType=LARGEINSTANTANEOUS.

Units Legal Range Default Required Variability
0 \(<\) whEff \(\leq\) 1 .82 No constant

whSBL

Type: float

Standby loss, used in modeling whType=LARGESTORAGE.

Units Legal Range Default Required Variability
Btuh x \(\ge\) 0 0 No constant

whPilotPwr

Type: float

Pilot light consumption, included in fuel energy use of DHWHEATERs with whHeatSrc=FUEL.

Units Legal Range Default Required Variability
Btuh x \(\ge\) 0 0 No hourly

whParElec

Type: float

Parasitic electricity power, included in electrical energy use of all DHWHEATERs.

Units Legal Range Default Required Variability
W x \(\ge\) 0 0 No hourly

whFAdjElec=float\

whFAdjFuel

Type: float

Water heater energy use modifiers. Multiplies calculated use of electricity (whFAdjElec) and fuel (whFAdjFuel). All components of energy use -- primary, backup, XBU (extra backup), and other auxiliary -- are modified before they are accumulated to whElecMtr and whFuelMtr.

Units Legal Range Default Required Variability
\(\ge\) 0 1 No subhourly

whElecMtr

Type: mtrName

Name of METER object, if any, by which DHWHEATER electrical energy use is recorded (under end use DHW).

Units Legal Range Default Required Variability
name of a METER Parent DHWSYS wsElecMtr No constant

whxBUEndUse

Type: choice

Specifies the whElecMtr end use, if any, to which extra backup energy is accumulated. In some water heater types, extra backup energy is modeled to maintain output temperature at wsTUse. By default, extra backup energy is included in end use dhwBU. whxBUEndUse allows specification of an alternative end use to which extra backup energy is accumulated.

Units Legal Range Default Required Variability
end use code (extra backup accums to dhwBU) No constant

whFuelMtr =mtrName

Name of METER object, if any, by which DHWHEATER fuel energy use is recorded (under end use DHW).

Units Legal Range Default Required Variability
name of a METER Parent DHWSYS wsFuelMtr No constant

whTankTInit =comma-separated list of 12 floats

A list of 12 initial values for HPWH tank model layer temperatures, in bottom-to-top order. If given, these values are used to initialize tank layer temperatures at the beginning of the warmup period. Initialization is not repeated at the beginning of the main simulation.

whTankTInit is allowed only for HPWH-based types (whHeatSrc=ASHPX or whHeatSrc=ResistanceX).

whTankTInit is intended for use in empirical validation studies where the initial tank state needs to match measured data. whTankTInit should not be generally used. In the absence of whTankTInit, layer temperatures are initialized to the water heater setpoint inherited from the parent DHWSYS.

Units Legal Range Default Required Variability
oF x \(\gt\) 0 No constant

endDHWHEATER

Optionally indicates the end of the DHWHEATER definition.

Units Legal Range Default Required Variability
x \(\geq\) 0 none No

Related Probes: