# EIRfPLR vs EIRfPLR&dT

For the chiller electric input ratio as a function of part load ratio chiller curve, IES-VE and eQuest both use EIRfPLR&dT, a bi-quadratic curve which requires 6 coefficients (a-f) and has two variables, PLR and lift (dT, ECWT and LCHWT).

But for `Chiller:Electric:EIR`

EnergyPlus seems to only allow "EIRfPLR" as a quadratic curve, with only one variable, PLR, and 3 coefficients (a-c).

It then doesn't appear that its possible to use use the same curve fits in IES-VE or eQuest as it is in EnergyPlus. There is a third option using `Chiller:Electric:ReforumlatedEIR`

but that equation is either bi-cubic, and depending on LCWT (not ECWT) and PLR, or a custom curve dependent on dT* and T*dev.

I found this because I created custom chiller curves for use in IES-VE, and wanted to run some tests in EnergyPlus, but found it wouldn't accept my bi-quadratic curve.

Can someone explain the theory behind why one of these curve fits should be used over another and which one is 'better', and confirm that its not possible to use the same curve in all softwares? Unless you are using, the EIRfPLR quadratic curve only since you can always use fewer coefficients, but not more.

Which object are you refering to?

`Chiller:Electric:EIR`

for eg uses 3 curves: CapfT, EIRfT, EIRfPLR (Engineering ref). It's the DOE 2.1 formulation, plus a couple new features to model stuff like evaporative condensers.@Julien Marrec, I've added more detail to my question to better explain what I am looking for. I'm specifically interested in the EIRfPLR curve, not CAPfT or EIRfT.

Do you have a link to the IES reference manual perhaps? Because reading the DOE2.1 Engineers manual (see here around page 575 of the PDF), eQuest uses the exact same formulation as E+ at least in DOE21 (I don't have windows so I don't have the latest eQuest to check)

Specifically, I'm interested to see the entire set of curves IES VE uses. Because if they use two curves, CapFT and EIRfPLR&dT, and E+ uses CapFT, EIRfPLR and EIRfdT, then it's just a different way of representing the same space.

IESVE uses the same the general 3 curve model from the old DOE2, see the link below around figure 3-107 (looks like the screen shot is a mistake and a copy of the previous curve, but the text below is right). The function of each curve seems to be the same as the DOE2 method, with the exception to the complexity of the EIRfPLR one that Anna mentioned, that she and I can’t figure out. Seems like mybe they’ve just adjusted the model slightly?

https://help.iesve.com/ve2018/electri...