[BLDG-SIM] Condenser Water Reset in eQuest

[Kevin Warren]

Condenser Water Reset in eQuestMike,

What great timing you have. I was grappling with this exact issue this
morning. You saved me some time.

There seems to be a work around for the issue of the min CW temp at the
chiller. You say that "the chiller has a keyword MIN-COND-T that defualts to
70F and cannot be changed from within eQuest". I could not find how to
change it within the main body of eQUEST either. However, it seems you CAN
change it in a parametric run. I did this and it seems to be reflected in
the chiller condenser water temp in my hourly report.

Kevin Warren, P.E., CEM, LEED AP
Warren Energy Engineering, LLC
(610) 255-3798 ph
(610) 255-3406 f
  -----Original Message-----
  From: BLDG-SIM at GARD.COM [mailto:BLDG-SIM at GARD.COM]On Behalf Of Mike Tillou
  Sent: Thursday, August 17, 2006 1:58 PM
  To: BLDG-SIM at GARD.COM
  Subject: [BLDG-SIM] Condenser Water Reset in eQuest




  Hi all..I thought I would share a couple of tips on using Condenser Water
Reset Strategies in eQuest . Hopefully some of you will find this useful.

  We just finished modeling a chiller plant where we looked at using low
condenser water temperatures ( below 60F ) as an energy efficiency measure.
The project is in a climate with very low wetbulb temperatures .  There are
a couple of quirks I thought I would share about trying to model a strategy
like this.

  The Condenser Loop Control tab has several options for resetting the loop
temperature.  If you notice MIN-RESET-T always defaults to 70F.

  Issue  #1:  If you reset the Condenser loop MIN-RESET-T lower than 70F
(say 65F) and then run an hourly report to check the loop temperature
everything looks like it's working fine.  BUT..if you also check the chiller
entering condenser temperature you will find it never goes below 70F even
though the condenser loop says it should be lower.  This is because the
chiller has a keyword MIN-COND-T that defualts to 70F and cannot be changed
from within eQuest.  You have to change the keyword manually in the input
file by adding the line, MIN-COND-T = 65 underneath the definition of your
chiller.


  The most likely reason this defaults to 70F is because the default chiller
performance curves were not designed for condenser temperatures below 70F
( someone should correct me if this is wrong)

  If you want to try and model condenser water temperatures below 70F I
highly recommend you create custom performance curves that include data
points that describe the operation of your chiller at the appropriate
condenser water conditions.

  That brings me to Issue #2.

  The MIN-COND-T keyword has a lower limit of 60F.  In other words even if
you create the appropriate performance curves  and then try to set
MIN-COND-T lower than 60F you will get a simulation error.

  You can work around this by using the DIAGNOSTIC keyword "NO-LIMITS".  In
effect this turns off both the Max and Min keyword limits.  You can then
simulate chiller operation with very low condesner water temperatures.

  If you use the "NO-LIMITS" keyword do so very carefully.  This is a very
important error checking function of DOE2.2 eQuest.

  Mike



  Michael Tillou, PE
  etc Group, Inc.
  PO Box 7, Williamstown, MA 01267
  ph. (413) 458-9870 fx. (413) 458-9875










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