I have further found that the low differential temperatures between supply and return happens when the loop is in heating mode only. When the loop has a cooling only load, the temperature differentials are as expected (I can send a test file directly if anyone is interested).<br>
<br>If the pump is cycling, then this should help maintain a higher difference in supply and return temperatures.<br><br>--<br>Karen<br><br><div class="gmail_quote">On Tue, Nov 24, 2009 at 1:51 PM, Steven Gates <span dir="ltr"><<a href="mailto:stvgates@pacbell.net" target="_blank">stvgates@pacbell.net</a>></span> wrote:<br>
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<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;">Doug/Karen,</span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;">Check out CIRCULATION-LOOP:LOOP-OPERATION
= SUBHOUR-DEMAND</span></font></p>
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<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;">For a loop of type WLHP or CW only, this
control strategy will cause the loop pump to cycle subhourly in accordance with
the cycling demands of the attached WLHP/DX units. However, it will not
affect the operation of a boiler/fluid-cooler that may also be attached to the
loop; those components are assumed to run for the entire hour.</span></font></p>
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<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;">Steve Gates</span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
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<p class="MsoNormal"><b><font size="2" face="Tahoma"><span style="font-size: 10pt; font-family: Tahoma; font-weight: bold;">From:</span></font></b><font size="2" face="Tahoma"><span style="font-size: 10pt; font-family: Tahoma;"> Doug Maddox
[mailto:<a href="mailto:DougM@TWGI.com" target="_blank">DougM@TWGI.com</a>] <br>
<b><span style="font-weight: bold;">Sent:</span></b> Tuesday, November 24, 2009
9:45 AM<br>
<b><span style="font-weight: bold;">To:</span></b> <a href="mailto:steve.gates@doe2.com" target="_blank">steve.gates@doe2.com</a><br>
<b><span style="font-weight: bold;">Subject:</span></b> Loop flow control in WLHP</span></font></p>
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<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;">Steve,</span></font></p>
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<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;">I saw the email below posted on the eQuest
email list. I checked it out in a test run and found the same problem.
My guess as to the cause is that if a heat pump runs for a fraction of an
hour, water valve is modeled as fully open for that entire hour, resulting in
excessive flow. Could that be the cause? If so, is there a simple
solution?</span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
<p class="MsoNormal" style="margin-bottom: 12pt;"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;">Thanks, </span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;">Doug
Maddox</span></font><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;"></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;">The Weidt Group</span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;">802-262-1033</span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
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<p class="MsoNormal"><b><font size="2" face="Tahoma"><span style="font-size: 10pt; font-family: Tahoma; font-weight: bold;">From:</span></font></b><font size="2" face="Tahoma"><span style="font-size: 10pt; font-family: Tahoma;">
<a href="mailto:equest-users-bounces@lists.onebuilding.org" target="_blank">equest-users-bounces@lists.onebuilding.org</a>
[mailto:<a href="mailto:equest-users-bounces@lists.onebuilding.org" target="_blank">equest-users-bounces@lists.onebuilding.org</a>] <b><span style="font-weight: bold;">On Behalf Of </span></b>Karen Walkerman<br>
<b><span style="font-weight: bold;">Sent:</span></b> Friday, November 20, 2009
2:12 PM<br>
<b><span style="font-weight: bold;">To:</span></b>
<a href="mailto:equest-users@lists.onebuilding.org" target="_blank">equest-users@lists.onebuilding.org</a><br>
<b><span style="font-weight: bold;">Subject:</span></b> [Equest-users] Loop
Operation</span></font></p>
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<p class="MsoNormal" style="margin-bottom: 12pt;"><font size="3" face="Times New Roman"><span style="font-size: 12pt;">Hi All,<br>
<br>
I'm having some issues with loop and pump operation in eQuest.<br>
<br>
I have tested this issue with water loop heat pump loops. Basically, I
set my loop design DT, but for many hours, the loop operates at very low
temperature differentials. With the given load on the loop, this requires
a high flow, and results in high pump energy!<br>
<br>
Specifically, for a heat pump loop, I'm expecting a 7-10 F difference in supply
and return temperatures at all times. I just ran a test model with a loop
design DT specified at 10 F. For hours when there is a heating only load
on the loop, I have an average difference in supply and return temperatures of
about 3 degrees. This requires the pump to move about 3 times more water
than necessary. My system is modeled with variable speed pumps, and
isolation valves at each heat pump.<br>
<br>
Any suggestions are greatly appreciated!<br>
<br>
Thanks,<br><font color="#888888">
<br>
--<br>
Karen</font></span></font></p>
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