VRF performance curve: EIR boundary temperature

asked 2019-01-14 11:12:03 -0600

171 ●1 ●6

I tried a simple case of VRF system with EnergyPlus v9.0. I reported the outputs "Performance Curve Input /Output Value" for the VRF model performance curve called "Cooling Energy Input Ratio Boundary Curve", which gave me a result of -999. However, the rest of the cooling curves have good values. In fact, the selection between the low and high cooling EIR curve seems to be following the boundary temperature curve for cooling capacity, not for EIR.

Can anyone confirm if this is a bug or correct me if I am wrong, please?

answered 2019-01-14 11:19:33 -0600

rraustad

13844 ●79 ●12 http://www.fsec.ucf.edu/

It appears your assessment is correct. The VRF model looks only at the cooling capacity boundary curve to calculate both the capacity and EIR modifiers. The code below shows the issue. This needs to be split out to test each boundary curve individually.

// recalculate cooling Cap and EIR curve output if using boundary curve along with dual Cap and EIR curves.
if (VRF(VRFCond).CoolBoundaryCurvePtr > 0) {
    CoolOABoundary = CurveValue(VRF(VRFCond).CoolBoundaryCurvePtr, InletAirWetBulbC);
    if (OutdoorDryBulb > CoolOABoundary) {
        if (VRF(VRFCond).CoolCapFTHi > 0) TotCoolCapTempModFac = CurveValue(VRF(VRFCond).CoolCapFTHi, InletAirWetBulbC, CondInletTemp);
        if (VRF(VRFCond).CoolEIRFTHi > 0) TotCoolEIRTempModFac = CurveValue(VRF(VRFCond).CoolEIRFTHi, InletAirWetBulbC, CondInletTemp);
    }
}