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

[James Hansen]

Sorry, meant that my condenser water entering temperature to the chiller follows the AHRI guidelines for condenser water reset (83 degrees at full load, going down to 65 degrees at 50% in a linear fashion, and then staying at 65 degrees down to 10%).

 

 

From: Paul Diglio [mailto:paul.diglio at sbcglobal.net] 
Sent: Monday, March 14, 2011 11:32 AM
To: James Hansen; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] which chiller curve(s) to modify?

 

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 <http://www.ghtltd.com/> 

 

 

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