[Equest-users] Loop to Loop Heat Pump (Josh Doherty)

[Kevin Kyte]

Josh,

You have several things to check, first the efficiencies of ground source heat pumps are usually higher than water sourse heat pumps.  Make sure the fan power and EIR inputs you have are accurate.  Also, make sure the unmet hours are reasonable, if unmet is still about 9% or more, it is probably not accurate.  Appropriate gas utility rates are important for GSX.  To name a few.
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Message: 2
Date: Mon, 11 May 2009 10:26:41 -0600
From: Josh Doherty <jdoherty at dcengineering.net>
Subject: [Equest-users] Loop to Loop Heat Pump
To: "equest-users at lists.onebuilding.org"
        <equest-users at lists.onebuilding.org>
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        <2A0D7A2F0234AF42A69CE7C89ACF65286A95FB8FD1 at dc-boi-ex01.dcengineering.local>

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I am trying to model a loop to loop heat pump that will take heat out of well water constantly at 50F and put it into a hot water loop at 125F.  I am using the loop to loop heat pump to model this design and it seems that things are working pretty good...except for the actual heat pump.  For whatever reason, the heat pumps are costing significantly more to operate than a boiler system.  However, with a COP of 3.5 and the current utility rates, the heat pumps should cost less to operate.

Does anybody have experience with the loop to loop heat pumps in eQuest and the associated performance curves that might shine some light on the problem here?  I am not sure if the loop to loop heat pump in eQuest is designed to model the system I have described and my thought is that something is going wrong with the performance curves.  Lastly, is there a way to "eliminate" the performance curves and have eQuest run the analysis assuming a constant COP=3.5?  This would allow me to see if the performance curves really are the issue.

Thank you all for your help and time!

Josh Doherty


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