I am trying to model a ground source heat pump system with a ground source
HX. The actual system includes the primary loop pump, Taco Loadmatch
circulators for the individual heat pumps (secondary) and a pump for the
well field. The well field pump flow is 50% of the HP loop flow. The
initial modeling results in full flow from the HP loop through the well
field which keeps the loop temperature low (typically 40s-50s). The
controls for the well field pump is to run the pump when the loop
temperature drops to 33F or exceeds 80F with a 10F "deadband" (pump stops at
43F and 70F). The primary and secondary pumping is not a direct issue as I
can run the model with the secondary pumps for their energy use and then
eliminate them for subsequent modeling. I have tried to assign the well
field pump to the HX under Attachments, but this fails to take. eQuest help
generally says to create a separate loop for the HX with its own pump.
However, I can not get this to go as there are no systems assigned to this
loop and get an error message for no load for design. The 50% flow through
the well field seems to create an issue with the primary/secondary loop flow
as it appears that primary flows in eQuest are expected to be greater than
or equal to secondary flows. (I have experienced a similar issue with
boiler water loops that draw a portion of the water from the main heating
loop.)

Any ideas on how to deal with this?

--
Ron Pecarina, PE, CEM, LEED-AP