Why are you using a separate lake/well loop and heat pump for the chilled water loop? You should be able to have the same piece of machinery attached to both a chilled water loop and a hot water loop. This way heat is transferred from one loop to the other when there are simultaneous loads. The ground loop is only used when there is net heating or cooling needed.<br>
<br>My beef with this system is that you can only use a loop type of lake/well using a constant condenser water temperature. This is usually not the case with ground loops, unless you are circulating water from an underground reservoir!<br>
<br>--<br>Karen<br><br><br><div class="gmail_quote">On Wed, Feb 4, 2009 at 11:38 AM, Tim Dion <span dir="ltr"><<a href="mailto:TimD@hargis.biz">TimD@hargis.biz</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div>
<div><span><font size="2" face="Arial">I'm modeling a
ground loop heat exchanger to provide condenser water to a large water-to-water
heat pump which will be capable of providing simultaneous heating and chilled
water to AHU coils in the building. The Water-to-water Heat Pump being designed
around is similar to that manufactured by Multistack, Heat-Harvester, Climacool,
etc.</font></span></div>
<div><span><font size="2" face="Arial"></font></span> </div>
<div><span><font size="2" face="Arial">I've successfully
created a 2-pipe water loop with a water-to-water heat pump that gets its'
condenser water from a ground loop heat exchanger (lake/well). When assigned to
Fan Coils in the building this system appears to work just fine. However, no
simultaneous heating/cooling capability.</font></span></div>
<div><span><font size="2" face="Arial"></font></span> </div>
<div><span><font size="2" face="Arial">So, I've now added a
chilled water loop with a second water-to-water heat pump that gets its'
condenser water from a seperate ground loop heat exchanger. I then assigned the
cooling coils to the chilled water loop and the heating coils to the 2-pipe
water loop. Trouble is I get the error that reads, "the chilled water loop has
no load". If I manage to get this error to go away then my zones have 5,000 +
hours of unmet heating loads. </font></span></div>
<div><span><font size="2" face="Arial"></font></span> </div>
<div><span><font size="2" face="Arial">I've been searching
the archives and I see that this has come up several times but with no real
solution other than "it should be able to be done". I'm posting the question
again in hopes that someone who has successfully modeled this system can point
the rest of us in the right direction. This type of system is coming up more and
more (I have 4 projects considering them now) and as we strive toward greater
building efficiency we are going to HAVE to be able to successfully model these
system types. </font></span></div>
<div><font size="2" face="Arial"></font> </div><font style="font-size: 10pt; font-family: Arial;">Tim Dion, LEED® AP
<br>Mechanical<br><b><span style="color: navy;">HARGIS ENGINEERS</span></b>
<br>600 Stewart Street <br>Suite 1000 <br>Seattle, WA 98101 <br><a style="color: rgb(128, 128, 128); text-decoration: none;" href="http://www.hargis.biz/" target="_blank">www.hargis.biz</a> <br><br><span style="color: gray;"><b>d | </b>206.859.5391</span> <br>
<span style="color: gray;"><b>o | </b>206.448.3376 </span><br><span style="color: gray;"><b> f | </b>206.448.4450</span> <br></font>
<div> </div></div>
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