In the EnergyPlus Engineering Reference (pg 909), the reverse-cycle defrost power is given as as function of both fractional defrost time and Runtime-fraction (RTF)
However, in the current source code (DXCoils.cc, (https://github.com/NREL/EnergyPlus/blob/405295034523d273e87403a268c96107e2c0d224/src/EnergyPlus/DXCoils.cc#L8391C4-L8403C5) around lines 8391–8403 in commit 4052950), the defrost power for reverse-cycle on-demand defrost is implemented as:
FractionalDefrostTime = 1.0 / ( 1.0 + 0.01446 / OutdoorCoildw ); ... DXCoil(DXCoilNum).DefrostPower = DefrostEIRTempModFac * ( DXCoil(DXCoilNum).RatedTotCap(Mode) / 1.01667) * FractionalDefrostTime;
i.e., it multiplies by FractionalDefrostTime but not by RTF.
Which formulation is intended to be correct: the Engineering Reference equation including RTF, or the current implementation without RTF? If the code is correct, how should the Engineering Reference equation be interpreted?
