I know there was a recent discussion about chiller curves, but I can't
seem to access www.gard.com right now, so I thought would send out this
email since I don't remember it being discussed.

I have two different curves for a standard water-cooled 200-ton screw
chiller:

1) EIR based on PLR, but with AHRI condenser relief

2) EIR based on PLR, with NO condenser relief, and varying return
chilled water temperature (from design at 100% to only about a 2 degree
delta between supply and return at the 20% load range)

Which curves should I modify with custom curves? I am so confused.

The f(PLR) curve says it should be the EIR vs PLR with no condenser
water reset. That one's the easy one. I already set that one up, and
it's about $1000 cheaper a year than the default curve, so I know it's
at least in the right range.

But the f(t evap leaving, t cond entering) says it's a quadratic curve,
but since there are two variables, shouldn't it be bi-quadratic like the
Cooling Capacity curve as a function of entering CW and leaving CHW?

When you all get chiller PLR curves with condenser relief, which
curve(s) do you modify and to what extent?

Thanks!

James Hansen, PE, LEED AP