Water to air heat pump are still sized to an infinite capacity

[lymereJ]

Issue overview

This issue is similar to #9805.

The capacity of one of the coil is sized to infinity:

Component Sizing Information, COIL:HEATING:WATERTOAIRHEATPUMP:EQUATIONFIT, DATACENTER_TOP_ZN_6 ZN PSZ-AC DATA CENTER WATER-TO-AIR HP HTG COIL, Design Size Rated Heating Capacity [W], INF

Running the defect file in the debugger shows that this is occurring because RatedHeatCapTempModFac which in this instance is == 0 is used here as a denominator. This is occurring because the value of the modifier is initialized to 0 and the heating design flow rate, while greater than 0, is very small so RatedHeatCapTempModFac is never updated because we check whether or not the flow rate is greater than a small airflow here:

EnergyPlus/src/EnergyPlus/WaterToAirHeatPumpSimple.cc

Lines 2320 to 2340 in b1b4068

	VolFlowRate = HeatingAirVolFlowRateDes;
	} else {
	VolFlowRate = CoolingAirVolFlowRateDes; // system air flow
	}
	// heating design day calculations
	if (VolFlowRate >= DataHVACGlobals::SmallAirVolFlow) {
	auto &finalSysSizing(state.dataSize->FinalSysSizing(state.dataSize->CurSysNum));
	if (state.dataSize->CurOASysNum > 0) { // coil is in the OA stream
	HeatMixTemp = finalSysSizing.HeatOutTemp;
	HeatMixHumRat = finalSysSizing.HeatOutHumRat;
	HeatSupTemp = finalSysSizing.PreheatTemp;
	} else { // coil is on the main air loop
	if (VolFlowRate > 0.0) {
	HeatOutAirFrac = finalSysSizing.DesOutAirVolFlow / VolFlowRate;
	HeatOutAirFracSys = finalSysSizing.DesOutAirVolFlow / RatedAirVolFlowRateDes;
	} else {
	HeatOutAirFrac = 1.0;
	HeatOutAirFracSys = HeatOutAirFrac;
	}
	HeatOutAirFrac = min(1.0, max(0.0, HeatOutAirFrac));
	HeatOutAirFracSys = min(1.0, max(0.0, HeatOutAirFracSys));

Details

Some additional details for this issue (if relevant):

• Platform: Windows
• Version of EnergyPlus: 23.1

Checklist

Add to this list or remove from it as applicable. This is a simple templated set of guidelines.

• Defect file added
• Ticket added to Pivotal for defect (development team task)
• Pull request created