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<title>Condenser Water Reset in eQuest </title>
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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>We are checking eQUEST to confirm the
issue of MIN-COND-T, and will fix it if it is missing.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Mike is correct that the capacity and
power performance curves were not fit for condenser temperatures below 65-70F,
and the default MIN-COND-T reflects this fact. The reason is because the
majority of chillers cannot operate satisfactorily much below this temperature.
For many reciprocating chilllers, the expansion valve requires a
minimum pressure differential in order to operate and deliver the rated
capacity. Centrifugal chillers may also be limited. Recently, we
were investigating a ‘frictionless’ centrifugal compressor, and learned
that motor cooling would be inadequate if the condenser temperature (and pressure)
drops much below about this value; insufficient liquid refrigerant would be
injected into the motor.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>If you want to investigate lower condenser
temperatures, we recommend that you inspect the capacity and eir curves in the
regime of interest to confirm whether they yield reasonable results.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The best way to use the DIAGNOSTIC
NO-LIMITS override is to first debug your input at a higher diagnostic level so
that the BDL can issue errors, warnings, cautions. Once you are ready to
run, then set NO-LIMITS.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Depending on feedback we get from people,
we can reduce the lower limit of MIN-COND-T, or change the error checking so
that it issues a warning rather than an error. As the curves are NOT fit
for temperatures lower than about 65F, the lower limit should probably remain
the same, but the checking reduced from an error to a warning. Comments?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Steve Gates<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
BLDG-SIM@GARD.COM [mailto:BLDG-SIM@GARD.COM] <b><span style='font-weight:bold'>On
Behalf Of </span></b>Mike Tillou<br>
<b><span style='font-weight:bold'>Sent:</span></b> Thursday, August 17, 2006
10:58 AM<br>
<b><span style='font-weight:bold'>To:</span></b> BLDG-SIM@GARD.COM<br>
<b><span style='font-weight:bold'>Subject:</span></b> [BLDG-SIM] Condenser
Water Reset in eQuest</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family: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.</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family: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. </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>The
Condenser Loop Control tab has several options for resetting the loop
temperature. If you notice MIN-RESET-T always defaults to 70F. </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family: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.</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>
</span></font><br>
<font size=2 face=Arial><span style='font-size:10.0pt;font-family: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) </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family: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.</span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>That
brings me to Issue #2.</span></font> <o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family: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. </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family: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. </span></font><o:p></o:p></p>
<p><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>If
you use the "NO-LIMITS" keyword do so very carefully. This is a
very important error checking function of DOE2.2 eQuest.</span></font><o:p></o:p></p>
<p><b><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial;
font-weight:bold'>Mike </span></font></b><o:p></o:p></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p style='margin-bottom:12.0pt'><b><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial;font-weight:bold'>Michael Tillou, PE<br>
etc Group, Inc.<br>
PO Box 7, Williamstown, MA 01267<br>
ph. (413) 458-9870 fx. (413) 458-9875</span></font></b><o:p></o:p></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<pre><font size=2 face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 face="Courier New"><span style='font-size:10.0pt'>==================<o:p></o:p></span></font></pre><pre><font
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