[bldg-sim] Turning one number into four..

[Mike Tillou]

John,

You can create custom bi-quadratic curves for each chiller (baseline and
proposed) in your analysis if you want a true "apples-to-apples"
comparison.  This is easy to do using data from the chiller manufacturer
and Microsoft Excel functions.

The more important question, could a user create a really bad ARI-550
compliant chiller and then compare it to an optimized as-designed
chiller and over-estimate the potential savings or is ARI-550 written
well enough that there isn't enough difference between compliant
machines?  

Mike

Michael Tillou, PE
ETC Group - Energy Engineering for a Sustainable Future
Ph:413-458-9870


-----Original Message-----
From: bldg-sim at gard.com [mailto:bldg-sim at gard.com] On Behalf Of Aulbach,
John
Sent: Thursday, February 08, 2007 5:54 PM
To: bldg-sim at gard.com
Subject: [bldg-sim] Turning one number into four..


Hi all:

The infamous "one equation, four unknowns".  Namely, IPLV (or NPLV, if
you are of that persuasion).

Utility incentive Programs and LEED say to use an ASHRAE 90.1-2004 code
chiller with a COP of xx and an IPLV of xx. As I understand it, IPLV is
a curve created as a standardization to compare chiller part load
characteristics, one to another.  However, no analysis program that I
know of (certainly not of the DOE-2/eQuest flavor) can extract such a
curve from a single number.

I believe you are losing out if a new high efficiency chiller with a 4
mile long condenser (just kidding) happens to perform quite well at part
load. You will not get a fair comparision, only the default program
curves.

Is there some accepted ASHRAE magic that will take an IPLV number and
make the 75%, 50%, and 25% kW/ton numbers, so that a true "apples and
apples" comparison between a code chiller and a super chiller can be
made?

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