[Equest-users] which chiller curve(s) to modify?

[Paul Diglio]

Jim:

What do you mean by condenser relief?

Paul Diglio




________________________________
From: James Hansen <JHANSEN at ghtltd.com>
To: equest-users at lists.onebuilding.org
Sent: Mon, March 14, 2011 11:23:04 AM
Subject: [Equest-users] which chiller curve(s) to modify?


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!
 
GHT Limited
James Hansen, PE, LEED AP
Senior Associate
1010 N. Glebe Rd, Suite 200
Arlington, VA  22201-4749
703-338-5754 (Cell)
703-243-1200 (Office)
703-276-1376 (Fax)
www.ghtltd.com
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