[BLDG-SIM] EQUEST: CW Temperature and Chiller Performance

[Mike Tillou]

David,
 
I think you are confusing two different issues.  The rated/design
chiller conditions used to calculate the EIR and the operation of the CW
loop are somewhat independent so your concern may be unecessary.  I
think this will help answer your question.  
 
First: 
When you define the design or rated conditions of the chiller you are
giving eQuest the information it needs to use the custom bi-quadratic
performance curves that describe how chiller power (EIR) changes for
different operating conditions.  Rated conditions refer to ARI
conditions of 44F LCHWT and 85F ECWT, while the design conditions refer
to the actual chiller design (Should only be used for chillers designed
at non-ARI conditions).  When you enter the chiller EIR and capacity you
need to make sure that they match the chillers rated or design
conditions that you enter.  
 
Second: 
The operation of the circulation loops (assuming a reset strategy is
being used) is dependent on the values you enter for COOL-SETPT-T,
COOL-SETPT-CTRL, MAX-RESET-T and MIN-RESET-T and not the chiller
design/rated conditions.  
 
The important thing in your case is that if your chiller is designed to
operate at low CW temperatures you probably want to create your own
chiller performance curves.   In my experience the default curves don't
give good results when the CW temp is that low (55F-65F especially at
full load) because they are intended for chillers operating much closer
to rated ARI conditions.  
 
The best way to check whether your data is good is to run an hourly
report on the chiller and then compare whether the corrected EIR for
certain ECWT and LCHWT conditions match the chiller manufacturer's rated
performance at those same conditions.
 
MIke
 
 
 
Michael Tillou, PE
etc Group, Inc.
PO Box 7, Williamstown, MA 01267
ph. (413) 458-9870 fx. (413) 458-9875
www.etcgrp.com


	-----Original Message-----
	From: BLDG-SIM at GARD.COM [mailto:BLDG-SIM at GARD.COM] On Behalf Of
Kenny, David
	Sent: Friday, June 09, 2006 4:36 PM
	To: BLDG-SIM at GARD.COM
	Subject: [BLDG-SIM] EQUEST: CW Temperature and Chiller
Performance
	
	

	I am attempting to model the chiller performance benefit
associated with reducing CW temperature.  However, I am running into
trouble.  The minimum CW loop temperature is defined at 55 degF.  The
return temperature is 65 degF.  However, eQuest is using a temperature
of 70 degF to calculate chiller performance.  The loop never gets above
65 degrees, so how is this possible?  I can not find a location in the
software where the entering CW temperature has been defined as 70 degF.

	 

	Any and all advice is appreciated!

	
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