[Bldg-sim] VRF modeling in Visual DOE (& other software) -- Software Limitations & LEED Rating

[Ravi Srinivasan]

Dear Building Simulationists!

We have come across several projects with VRF systems. Although several
publications, including the ASHRAE Journal (April 2007) issue's article
"Variable Refrigerant Flow Systems" by William Goetzler discusses in detail
VRF systems and its efficiency, the limitations of energy modeling software
does not permit to accurately model such systems.

Any insight into the following is much appreciated:

(1) Has anyone had luck modeling a VRF system in Visual DOE? (or EnergyPlus
or eQuest); I "heard" Trace can model VRF system -- can anyone confirm?
Currently, the only way to model a VRF system (in VDoE) is to select "PTAC"
or "PSZ" and modify EER values of the cooling unit. But, this is not even
close to the savings one can achieve in reality. This does not take into
consideration the capacity (heat) of the refrigerant (R-410a, for example).
Is there a procedure developed by ArchEnergy or others energy software
developers to accommodate such systems?

(2) Buildings (or owners / developers) should not be penalized due to the
limitations of energy modeling software!
If ASHRAE 90.1-2004 can stipulate a 10% reduction in LPD for introducing
"Occupancy sensors" in the building, why not introducing a reduction (as a
percentage) for VRF integration until the software are "upgraded"? Why
cannot USGBC accept a flat rate (say, 20% savings) if a VRF system is
integrated in the building?

Need your insight & inputs!

Good day!

RAVI SRINIVASAN (PhD), CEM, LEED AP, Assoc AIA
CEO & Head, Building Energy & Sustainability
SILPA INC
s i m p l e  .  s c i e n t i f i c   .   s u s t a i n a b l e
www.silpainc.com


AMERICAS: Philadelphia PA, Archer FL    |     MIDDLE EAST: Dubai, UAE     |
    INDIA: Hyderabad & Chennai
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