Load Conversion issue when switching from System:Unitary to System:UnitarySystem
I used HVACTemplate to model a central air-conditioning system with a natural gas furnace for heating, using the Direct Expansion Cooling Packaged and Split System options (Thermostat, Zone:Unitary, and System:Unitary).
I now want to convert the heating source from natural gas to electricity while using the same HVACTemplate group, but switching from System:Unitary to System:UnitarySystem so that I can model a heat pump.
Before proceeding, I wanted to confirm that I was not altering the original case and that I could achieve an “apples-to-apples” comparison. To do this, I defined the natural gas furnace in System:UnitarySystem with the same performance parameters (e.g., efficiency, COP) used in System:Unitary. However, the resulting energy consumption was higher than the original case (9,800 kWh vs. 8,100 kWh).
Next, I set all heating coil performance curve coefficients (Curve:Quadratic, Curve:Cubic, and Curve:Biquadratic) to zero, keeping only the Constant (Coefficient1) equal to 1. In this case, the heating energy consumption became lower than the original (7,100 kWh vs. 8,100 kWh).
Cooling results were consistent and did not change when I switched from System:Unitary to System:UnitarySystem.
Could anyone help explain why these differences occur and how to correctly match the results? Thanks!
@Hevar what simulation tool are you using? Please mention it in the title or body of your post, as well as add a tag so that others can provide better help.