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

[Bishop, Bill]

Nick,
You can use a chiller of TYPE = HEAT-PUMP to model W2W GSHP. You attach it/them to a CHW loop of TYPE = PIPE2 (a two-pipe loop) that provides either hot or cold water but never at the same time, and configure the switchover using the Operation and Controls tabs of the loop. You can also add condensing boiler(s) to the two-pipe loop and stage them with the W2W chiller(s) using Equipment Controls and Load Management in the loop Controls tab. The GSHP connection to the ground loop is via a LAKE/WELL CW loop, to which you can attach a GROUND-LOOP-HX of TYPE = LAKE/WELL. You have to specify the temperatures of the HX in the LOOP-TEMP-SCH (they are not calculated hourly like they are for the other GHX types) or eQUEST will default to the monthly ground temperatures from the weather file.
I would look into the heating-only Systems 9/10 in 90.1-2010 for spaces with no cooling.
Regards,
Bill

William Bishop, PE, BEMP, BEAP, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nick Patsos
Sent: Friday, February 07, 2014 7:00 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Water to water geothermal heat pump / Radiators / No cooling / Natural ventilation

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 ideas?

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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