DHWHeater

Name Type Variability Description/Comments
mult FLOAT_GEZ Start of run
  • count of identical water heaters (default 1)
  • models as if repeated identical input
  • non-integral values allowed re sizing methods
heatSrc choice:WHHEATSRC input time
  • heat source
  • C_WHHEATSRCCH_ELRES: electric resistance
  • _FUEL: fuel-fired burner
  • _ASHP: air source heat pump (T24DHW.DLL model)
  • _ASHPX: air source heat pump (Ecotope HPWH)
  • _ELRESX: electric resistance (Ecotope HPWH)
type choice:WHTYPE input time
  • heater type
  • C_WHTYPECH_STRGSML, _STRGLRG, _INSTSML, _INSTLRG,
  • _INSTUEF, _BUILTUP
desc ANAME input time probe-able description text
fcn number Start of run function of this DHWHEATER per whfcnXXX enum
Name Type Variability Description/Comments
ashpTy choice:WHASHPTY input time
  • air source heat pump (HPWH) type, required iff wh_heatSrc=ASHPX, else ignored
  • C_WHASHPTYCH_xxx, etc
resTy choice:WHRESTY input time
  • resistance heater type, used iff wh_heatSrc=_ELRESX, else ignored
  • C_WHRESTYCH_xxx, etc
  • documentation only (9-2021)
znTi TI input time
  • [DHWHEATER][dhwheater] location zone re tank loss
  • 0 iff wh_tEx being used
  • heat losses go to half to zone air / half radiant
tEx number Start of subhour
  • surrounding temperature, F for tank loss
  • when wh_tEx set
  • - wh_znTi ignored
  • - heat loss discarded
ashpSrcZnTi TI input time
  • ASHP source zone
  • 0 iff wh_ashpTSrc being used
  • input heat removed from zone air
ashpTSrc number Start of subhour
  • ASHP source temperature, F
  • when wh_ashpTSrc set
  • - wh_ashpSrcZnTi ignored
  • - heat transfer ignored
ashpResUse FLOAT_GZ input time
  • resistance heat parameter for
  • Ecotope HPWH model iff C_WHASHPTYCH_GENERIC
  • default = 7.22, units / meaning unknown
tankTInit[index] FLOAT_GZ Array [DIM_DHWTANKTINIT] Start of run
  • initial tank layer temperatures for HPWH types, F (12 values)
  • [0]=bottom layer / [11]=top layer
  • HPWH tank model layer temps initialized at beginning of warmup
  • (not reinitialized at beg of simulation)
  • [0]=bottom layer / [11]=top layer
tankCount FLOAT_GZ Start of run
  • # of storage tanks per [DHWHEATER][dhwheater], re built-up whType=Builtup (default=1)
  • note does *not* reflect wh_mult (wh_mult=2, wh_tankCount=3 -> 6 tanks)
heatingCap FLOAT_GZ Start of run
  • Nominal heating capacity, Btuh
  • available only for limited HPWH types
vol FLOAT_GEZ Start of run
  • total storage vol, gal (actual, not rated; not per tank)
  • HPWH types: sets vol (default from preset)
  • other types: documentation only (default 50)
volRunning FLOAT_GZ input time
  • running storage volume = vol above aquastat, gal
  • HPWH compressor types: determines reqd total volume based on
  • aquastat position; see HPWHLINK::hw_DeriveVolFromVolRunning()
UA FLOAT_GEZ Start of run
  • HPWH-type total UA, Btuh/F (not per tank)
  • default from HPWH preset
insulR FLOAT_GZ Start of run
  • HPWH-type tank insulation resistance, hr-F/Btuh
  • default from preset or wh_UA and wh_vol
inHtSupply number input time
  • fractional tank height of supply inlet (0=bottom, 1=top)
  • default 0, HPWH models only
inHtLoopRet number input time
  • fractional tank height of loop return inlet(s) (0=bottom, 1=top)
  • default 0, HPWH models only
EF FLOAT_GZ input time rated energy factor
LDEF FLOAT_GZ input time load-dependent energy factor
UEF FLOAT_GZ input time
  • rated uniform energy factor
  • re C_WHTYPECH_INSTUEF
ratedFlow FLOAT_GZ input time max rated flow per UEF test, gpm
annualFuel FLOAT_GEZ input time annual fuel use per UEF method, therms/yr
annualElec FLOAT_GEZ input time annual electricity use per UEF method, kWh/yr
Name Type Variability Description/Comments
cycLossFuel number Start of run derived startup fuel use (=cyclic loss) for INSTUEF, Btu/cycle
cycLossElec number Start of run
  • derived startup electricity use (=cyclic loss) for INSTUEF, Btu/cycle
  • unused in revised model, 5-25-2017
maxFlowX number Start of run derived max flow for INSTUEF, gal-F/tick
maxInpX number Start of run input at max flow, Btu/tick
Name Type Variability Description/Comments
eff FLOAT_GZ input time efficiency (aka recovery efficiency)
SBL FLOAT_GEZ input time standby loss, Btuh
pilotPwr FLOAT_GEZ Start of hour
  • pilot light power, Btuh
  • included in wh_inFuel
parElec FLOAT_GEZ Start of hour parasitic electric use, W
tHWOutNoMix number End of subhour
  • most recent unmodified hot water temp, F
  • HPWH-only at tick end
  • does NOT include XBU
tHWOut number End of subhour
  • average hot water temp, F (at water heater)
  • HPWH: as delivered by model (subhr average of tick calls)
  • includes XBU: wh_tHWOut >= [DHWSYS][dhwsys].ws_tUse
  • other: [DHWSYS][dhwsys].ws_tUse
stbyTicks number Start of subhour
  • time since last draw, for HPWH and INSTUEF, ticks
  • re startup (cyclic) loss model
Name Type Variability Description/Comments
loadCFwdF FLOAT_GEZ input time
  • load carry-forward allowed (user input frac of capacity)
  • = approx # of hours [DHWHEATER][dhwheater] is allowed to meet
  • load that is unmet on 1 min basis
  • default = 1; only for C_WHTYPECH_INSTUEF
loadCFwdMax DBL input time
  • max load carry-forward energy (from wh_loadCFwdF), Btu
  • any excess load met via wh_qXBU
loadCFwd DBL Start of subhour
  • current load carry forward, Btu
  • see wh_InstUEFDoSubhr()
nTickFullLoad number End of subhour INSTUEF: current subhour equiv full load ticks (fractional)
nColdStarts DBL Start of subhour INSTUEF: current subhour # of cold startups
Name Type Variability Description/Comments
effSh FLOAT_GZ End of subhour
  • current subhour efficiency, used to support former hourly
  • models within tick calcs
  • unset (= 0) for full tick models (HPWH and INSTUEF)
Name Type Variability Description/Comments
operElec number Start of run
  • electrical power during operation at rating conditions, Btuh
  • never input, derived for INSTUEF
stbyElec FLOAT_GEZ Start of run
  • electrical power during standby, W
  • default=4, used for INSTUEF
Name Type Variability Description/Comments
resHtPwr FLOAT_GEZ input time
  • upper element resistance heating power, W
  • used for some models only
  • default = 4500
resHtPwr2 FLOAT_GEZ input time
  • lower element resistance heating power, W
  • default = wh_resHtPwr
Name Type Variability Description/Comments
HPWH
  • interface to Ecotope HPWH detailed heat pump model
  • also used for resistance electric heaters
HPWHLINK
Name Type Variability Description/Comments
HPWH.HSCount number End of subhour # of HPWH heatsources in use for current config
HPWH.tEx number End of subhour tank surround temp, F
HPWH.tASHPSrc number End of subhour temp of heat pump air source, F
Name Type Variability Description/Comments
HPWH.nQTXNodes number End of subhour
  • # of tank 1/12s used in hw_qTX extra tank heat
  • corresponds to nodes for HPWH default 12 node setup
Name Type Variability Description/Comments
HPWH.fMixUse number End of subhour
  • factor for draw adjustment re HPWH setpoint > [DHWSYS][dhwsys]::ws_tUse
  • Some HPWHs (e.g. SANCO2) have fixed (high) setpoints
  • draws are reduced to balance load at ws_tUse.
HPWH.fMixRL number End of subhour
  • factor for loop return flow adjustment re HPWH setpoint > [DHWSYS][dhwsys]::ws_tUse
  • Some HPWHs (e.g. SANCO2) have fixed (high) setpoints
  • Loop return flow is reduced to balance load at ws_tUse.
Name Type Variability Description/Comments
HPWH.inElec[index] DBL Array [2] End of subhour
  • current subhr HPWH electricity use, kWh
  • [0]=primary(=compressor or non-HP resistance) + misc
  • [1]=resistance backup (iff HP) (not including hw_HPWHxBU)
HPWH.heatAdded[index] DBL Array [2] End of subhour
  • current subhr HPWH heat added to water, kWh
  • [0]=primary(=compressor or non-HP resistance)
  • [1]=resistance backup (iff HP) (not including hw_HPWHxBU)
HPWH.tOut DBL End of subhour
  • last tick HPWH outlet temp, C
  • 0 if no draw
HPWH.tOutCHDHW DBL End of subhour
  • last tick output temp available to CHDHW, F
  • 0 if no draw
HPWH.HPWHxBU number End of subhour
  • current subhr HPWH add'l backup resistance heat, Btu
  • output water heated to ws_tUse iff HPWH output temp < ws_tUse
HPWH.qEnv DBL End of subhour
  • current subhr heat removed by HPWH from environment, kWh
  • + = to water heater; for 1 [DHWHEATER][dhwheater] (no wh_mult)
HPWH.qLoss DBL End of subhour
  • current subhr HPWH standby losses, kWh. + = to surround
  • for 1 [DHWHEATER][dhwheater] (no wh_mult)
HPWH.qHW DBL End of subhour
  • current subhr HPWH total delivered hot water heating, kWh. always >= 0
  • for 1 [DHWHEATER][dhwheater] (no wh_mult)
  • calc'd from flows and temp diffs (unlike hw_heatAdded)
  • includes heat to [DHWLOOP][dhwloop] and CHDHW, does not include hw_HPWHxBU
HPWH.qTX DBL End of subhour current subhr extra heat tank heat added, kWh (not Btu)
Name Type Variability Description/Comments
HPWH.tankHCNominal number End of subhour
  • nominal HPWH tank heat content, kWh (at 40 C)
  • used as normalizing factor for energy balance checks
HPWH.tankHCBeg DBL End of subhour current step beginning tank heat content, kWh
HPWH.tankHCEnd DBL End of subhour current step end tank heat content, kWh
Name Type Variability Description/Comments
HPWH.tHWOutF DBL End of subhour current substep working total re calc of hw_tHWOut
HPWH.nzDrawCount number End of subhour current substep # of draws > 0
HPWH.tHWOut number End of subhour
  • average hot water temp, F (at water heater)
  • includes XBU: hw_tHWOut >= ws_tUse
  • calc'd at substep end only
Name Type Variability Description/Comments
HPWH.bWriteCSV number End of subhour write HPWH debugging CSV iff nz
Name Type Variability Description/Comments
HPWH.qBal DBL End of subhour current step HPWH heat balance, kWh (s/b 0)
HPWH.balErrCount number End of subhour annual count of energy balance errors
HPWH.balErrMax DBL End of subhour maximum substep energy balance error for run, kWh
Name Type Variability Description/Comments
qXBU number End of subhour
  • current step HPWH add'l backup resistance heat, Btu
  • output water heated to ws_tUse iff HPWH output temp < ws_tUse
qEnv DBL End of subhour
  • current step heat removed by HPWH from environment, Btu
  • + = to water heater; for 1 [DHWHEATER][dhwheater] (no wh_mult)
qLoss DBL End of subhour
  • current step HPWH standby losses, Btu. + = to surround
  • for 1 [DHWHEATER][dhwheater] (no wh_mult)
qHW number End of subhour
  • current step hot water heating, Btu. always >= 0
  • for 1 [DHWHEATER][dhwheater] (no wh_mult)
  • DHW+[DHWLOOP][dhwloop]+CHDHW; does not include wh_qXBU
nzDrawCount number End of subhour current substep # of draws > 0
Name Type Variability Description/Comments
totHARL DBL End of hour
  • cumulative (year to date) recovery load at heater, Btu
  • = SUM( HARL) (includes losses, solar etc)
  • for single heater (wh_mult not applied)
hrCount number End of hour
  • # of hourly values included in wh_totHARL
  • re calc of avg
totOut DBL End of hour
  • cumulative (year to date) total heat delivered to hot water, Btu
  • includes wh_qXBU
Name Type Variability Description/Comments
fAdjElec FLOAT_GEZ Start of subhour
  • electricity use adjustment factor
  • applied to all electricity use (primary, BU, XBU)
  • default 1
fAdjFuel FLOAT_GEZ Start of subhour
  • fuel use adjment factor
  • applied to fuel use
  • default 1
  • energy inputs for current subhour, Btu
  • subhour results accumulated here
  • for single WH (wh_mult / ws_mult not applied)
Name Type Variability Description/Comments
inElecSh number End of subhour
  • primary electricity (including wh_parElec) (note not kWh)
  • for HPWH, includes compressor + misc (not resistance)
inElecBUSh number End of subhour
  • backup electricity (>0 only for HPWH resistance heat)
  • (does not include wh_inElecXBUSh)
inElecXBUSh number End of subhour XBU "extra" backup (reheating to maintain ws_tUse)
inFuelSh number End of subhour fuel (including wh_pilotPwr)
  • energy inputs for current hour, Btu
  • set from analogous subhour values
  • for single WH (wh_mult / ws_mult not applied)
Name Type Variability Description/Comments
inElec number End of hour
  • primary electricity (including wh_parElec) (note not kWh)
  • for HPWH, includes compressor + misc (not resistance)
inElecBU number End of hour
  • backup electricity (>0 only for HPWH resistance heat)
  • (does not include wh_inElecXBU)
inElecXBU number End of hour XBU "extra" backup (reheating to maintain ws_tUse)
inFuel number End of hour fuel (including wh_pilotPwr)

annual total energy inputs, Btu (check figures)

Name Type Variability Description/Comments
inElecTot DBL End of run annual total electricity, Btu
inFuelTot DBL End of run annual total fuel, Btu
Name Type Variability Description/Comments
elecMtri TI input time meter for system electricity use (default = parent ws_elecMtri)
fuelMtri TI input time meter for system fuel use (default = parent ws_fuelMtri)
xBUEndUse choice:ENDUSE input time
  • wh_elecMtri end use for separate accounting of wh_HPWHxBU
  • default = none (include wh_HPWHxBU in end use dhwBU)
Name Type Variability Description/Comments
unMetSh number End of hour
  • count of subhrs in this hour
  • when wh_tHWOut < wh_tUse
  • HPWH only?
unMetHrs number End of run
  • annual count of hrs having any wh_unMetSh
  • HPWH only?
balErrCount number End of subhour
  • annual count of energy balance errors
  • HPWH only?
Name Type Variability Description/Comments
tInlet number End of hour
  • hour avg inlet temp, F
  • reflects solar, DWHR, mixdown, ...
draw number End of hour
  • hour total draw seen by this [DHWHEATER][dhwheater], gal
  • check figure