Understanding Part Load Factor Performance Curves in EnergyPlus
I am relatively new to EnergyPlus and I am currently studying the documentation as well as all the guides/examples included with the software. At the moment, I am trying to better understand how part load performance is modeled in EnergyPlus for something like a residential gas furnace. I am hoping someone can provide a little clarification on some of the requirements for defining a part load factor (PLF) performance curve for a fuel-fired air heating coil.
According to the engineering manual, the PLF curve, which is a function of the part load ratio (PLR) has to following the following rules:
- PLF > = 0.7
- PLF > = PLR
While I think I understand the second requirement, the first seems somewhat arbitrary to me and I have not been able to find justification for why PLF must be greater than 0.7. This requirement of the PLF curve appears for other HVAC equipment as well.
If anyone is able to provide clarification on this requirement it would be greatly appreciated.
