[Equest-users] Water to water geothermal heat pump / Radiators / No cooling / Natural ventilation

Nick Patsos nick.patsos at gmail.com
Fri Feb 7 04:00:18 PST 2014

Hello all,

I need your opinions on a very complex system that I have to model for LEED
in eQuest.

The system is a water to water geothermal heat pump capable of producing
hot water for heating and in the summer season chilled water for cooling,
not simultaneously.

The hot water is to be used by low-temp radiators (no fans) in spaces or
FCUs. In some spaces ERV ventilators provide fresh air (constant speed) /
in some only natural ventilation is provided (significant issues there to
be discussed in due time).

There are spaces which have no heating/cooling by FCUs, only radiators
(with ERVs or without).

I have made a diagram to give a quick overview picture attached.

The issues are as follows:

1) I tried modelling a Loop-to-loop heat pump system producing both hot and
chilled water but I find significant consumption in cooling (coincident
with heating) in the winter months which is highly unusual, thus very
increased overall consumption in comparison with the baseline packaged VAV
(PVAVS) system. Any alternatives ?

2) For the not cooled spaces I used baseboard heating and as system PVAVS
cooling (due to the same as baseline cooling condition), I don't know if
this is the correct approach. For the fan power of PVAVS do I have to use
the same as baseline kW/cfm ? What about when the system is in heating when
only baseboards should work (no fans) ? How 's this to be modeled ? Any

3) For the geothermal loop, I have a ground loop heat exchanger, now
modelled as Lake/Well (due to limitations of the Loop to Loop heat pump)
but in reality it will be a straight pipe closed circuit loop. I remember
reading about creating a custom temp. schedule to model the exchanger, is
it possible ?

4) Something more obvious than the above but still unsure, is PVAVS in
eQuest the way to model Packaged VAV with Reheat as in 90.1 ?

5) Has anyone successfully tried the Shermad-Grimsrud method for natural
ventilation in eQuest ?

As you see, it is really messed up, mostly due to the water-to-water heat
pump. I know that I'm asking lots of questions in different topics at once.
Ideas in any of the topics are greatly appreciated.

Nikos Patsos
Mechanical Engineer
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