[Equest-users] Water Cooled VRF

Otto Schwieterman oschwieterman at fhai.com
Tue Dec 11 13:39:35 PST 2012


I have modeled a water-cooled VRF project and I used a Lake/Well system as the condensing loop. This was a water-cooled VRF project with a geothermal well field. I took the geothermal loop temperature calculations from a geothermal sizing program and scheduled the ground loop temperature in eQUEST. 

You can create custom performance curves (or use the GSHP/WLHP curves for quicker but less accurate results) and use a dual speed compressor (the variable speed compressor did not work for me either) for the VRF system. 

Good luck,


From: Tim Johnson [mailto:timj at ctagroup.com] 
Sent: Tuesday, December 11, 2012 11:12 AM
To: <equest-users at lists.onebuilding.org>
Subject: [Equest-users] Water Cooled VRF


I am attempting to model a water cooled VRF system for a dormitory in northern Montana.  I have used Dana Troy's method for air source VRF systems several times with great success, but this is my first attempt at a water source system.  The model seems to work as expected with a single speed compressor, but when I change this to a variable speed compressor, the system doesn't function properly.  There is no flow in the water loop and the VRF heating energy disappears.  The model still shows no unmet load hours but is clearly not operating correctly.


I have done some research in the help files and the forum archives and found little help.  Volume 3 of the DOE2 help file under Air-Side System Types - PVVT seems to hint at variable speed compressors being only for air cooled condenser types.  The eQUEST forums have a few posts of this same question with no conclusion.  What have you found?  What is the best way to simulate a variable speed compressor for a water source heat pump system?  Am I missing something here?






Tim Johnson, PE, BEMP, LEED AP
CTA : Mechanical Engineer  
DIRECT: 208.577.5645
CTA, Inc. |  www.ctagroup.com <http://www.ctagroup.com/> 
1185 W. Grove St. – Boise, ID 83702
P: 208.336.4900 – F: 208.343.3531

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