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<P><FONT SIZE=2 FACE="Arial">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.</FONT></P>
<P><FONT SIZE=2 FACE="Arial">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. </FONT></P>
<P><FONT SIZE=2 FACE="Arial">The Condenser Loop Control tab has several options for resetting the loop temperature. If you notice MIN-RESET-T always defaults to 70F. </FONT></P>
<P><FONT SIZE=2 FACE="Arial">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.</FONT></P>
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<BR><FONT SIZE=2 FACE="Arial">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) </FONT></P>
<P><FONT SIZE=2 FACE="Arial">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.</FONT></P>
<P><FONT SIZE=2 FACE="Arial">That brings me to Issue #2.</FONT>
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<P><FONT SIZE=2 FACE="Arial">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. </FONT></P>
<P><FONT SIZE=2 FACE="Arial">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. </FONT></P>
<P><FONT SIZE=2 FACE="Arial">If you use the "NO-LIMITS" keyword do so very carefully. This is a very important error checking function of DOE2.2 eQuest.</FONT></P>
<P><B><FONT SIZE=2 FACE="Arial">Mike </FONT></B>
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<P><B><FONT SIZE=2 FACE="Arial">Michael Tillou, PE<BR>
etc Group, Inc.<BR>
PO Box 7, Williamstown, MA 01267<BR>
ph. (413) 458-9870 fx. (413) 458-9875<BR>
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