[Equest-users] Water Cooled VRF

Tim Johnson timj at ctagroup.com
Tue Dec 11 08:12:12 PST 2012

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 APCTA : Mechanical Engineer  DIRECT:
208.577.5645 CTA, Inc. |  www.ctagroup.com1185 W. Grove St. – Boise, ID
83702P: 208.336.4900 – F: 208.343.3531
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