Modeling ground loop heat pumps

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Dear All:

I am trying to model a ground loop heat pump system in equest, but I keep
getting the following errors: " WLHP loop: Ground Loop has exceeded a
hi/low alarm limit and will shut down associated HVAC equipment for the
hour. Loop T: 17.91 Limit: 20.00. Verify that alarm limits are
reasonable, verify primary equipment sizing, especially ground-loop
heat-exchangers, and verify that the HP performance curves are suitable for
the intended operating range." as well as "Ground-loop HX: Ground Loop Heat
Exchanger 1 is undersized for the load and is producing an extreme
temperature of -4F."

Since the design is a closed loop system (vertical pipes) I have created a
GLHE of type 'Vertical Well-Sweden G-function', connected to a circulation
loop of the type 'water loop heat pump'. I have also inserted the GSHP
curves from DOE 22. I'm not sure if the problem is the parameters I have
defined in the model, or from the way I have set things up in EQUEST. I
would really appreciate it if someone with more experience than me can help
me out with my problem.

Best Regards,

Behnam Jowkar, MASc, BEng, LEED GA

behnam jowkar2's picture
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Behnam,

Loop field design has a lot of parameters. I suggest beginning with an autosize in eQuest based on the fairly standard design parameters of 200' deep, 15' oc spacing, ~15% glycol, ...

Adjust the quantity of boreholes until you meet the load.

There is much more detail that can be shared but if you're not familiar with GSHP in eQuest it will get you started.

- Matt H
Sent from mobile, please excuse typos.

Matt R Hein's picture
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