[BLDG-SIM] Mysterious eQuest result..

[Brandon Nichols]

John,

You may want to look into exactly what eQuest definition of a chiller reset temperature schedule is ... from my experience as a chiller plant engineer, the reset schedule you describe sounds like the reset of chilled water supply temperature based on outside air temperature, a function commonly found in chiller control panel software.  For example then, at 95°F OAT the chilled water supply temperature would be say 45°F, and at 70°F OAT the chilled water supply temp would be something like 55°F.

What parameter has the "setpoint" of 80°F?  The indoor space temperature, I presume... but doublecheck to make sure it's not something you're not expecting, like perhaps the chilled water supply.  If that checks out, than I would check to see if the low end of the reset schedule is holding the chillers on longer than expected, as would be indicated by a significant difference in chiller run hours between the 70°F stop and the 50°F reset schedule endpoint.


Hope that helps...

Brandon Nichols, PE
Mechanical
HARGIS ENGINEERS
600 Stewart St
Suite 1000
Seattle, WA 98101
d | 206.436.0400 c | 206.228.8707
o | 206.448.3376 f | 206.448.4450
www.hargis.biz




-----Original Message-----
From: BLDG-SIM at GARD.COM [mailto:BLDG-SIM at GARD.COM] On Behalf Of Aulbach, John
Sent: Tuesday, October 24, 2006 1:25 PM
To: BLDG-SIM at GARD.COM
Subject: [BLDG-SIM] Mysterious eQuest result..

Has anyone had this problem?

I have two 215 ton VFD centrifugal chillers running in an office building in Salt Lake City (in eQuest, that is). I have the setpoint temp set to 80°F, the setpoint control to Load-Rest, the Max Rest Temp to 95°F, and the Min rest temp to 70°F. The latter is required for an ASHRAE-90.1-2001 Base Case model.

I reset the Min reset temp to 50°F, per manufacturer's telling me I could do so, to take advantage of colder .

To my utter amazement, the heat rejection kWh went up 10 TIMES !! Same chiller, same everything else (as far as I know).

Am I doing this correctly? What is happening?

John R. Aulbach, PE, CEM
Project Manager
Nexant, Inc.
100 North Barranca, Suite 820
West Covina, CA 91791 USA
Phone: 626-430-9054
Fax: 626-430-9060
email: jaulbach at nexant.com
 

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