AirLoopHVAC:UnitarySystem heating PartLoadRatio calculation for cycling fan has NoHeatOutput > 0
I used Resstock 3.2.0, building_id = 2359, with the GSHP measure. The system is a AirLoopHVAC:UnitarySystem with Coil:Cooling:WaterToAirHeatPump:EquationFit and Coil:Heating:WaterToAirHeatPump:EquationFit, Fan:SystemModel.
The fan speed control method = "Discrete" and supply fan operating mode schedule set to 0 so the system has a cycling fan.
I noticed GROUND SOURCE HEAT PUMP HTG COIL:Heating Coil Part Load Ratio [](Hourly) reports a lower value compared to GROUND SOURCE HEAT PUMP HTG COIL:Heating Coil Heating Rate [W](Hourly) / Rated Heating Capacity, e.g. 0.453 vs 0.527, about 15% less.
Based on the engineering manual, formula 16.284,
And from Section 16.5.1.6, "If the supply air fan
cycles with the compressor, then the sensible heating energy rate is zero when the compressor is
OFF." So I would expect PartLoadRatio be similar to GROUND SOURCE HEAT PUMP HTG COIL:Heating Coil Heating Rate [W](Hourly) / Rated Heating Capacity but couldn't figure out why the lower values were reported from the model.
For the cooling coil, GROUND SOURCE HEAT PUMP Clg COIL:Cooling Coil Part Load Ratio [](Hourly) is very close to GROUND SOURCE HEAT PUMP Clg COIL:Cooling Coil Total Cooling Rate [W](Hourly) / Rated Cooling Capacity for each hour.
Is there anything else that affects the PartLoadRatio calculation for heating coils?
