Thanks for your perfect reply!
---????---
???: "Nick Caton"
????: 2014?09?30? 07:15:19
???: "'????'"<503271081 at qq.com>;"'Equest-users'"
??: RE: [Equest-users] ???The results of your email commands
I was just looking into this recently.
For VRF systems, I?ve seen direction to use PSZ, PVVT, and PTAC. PVVT is the approach endorsed/outlined by the Oregon energy trust in a powerpoint PDF that has made the rounds here on the lists a few times, and as such is probably ?most suggested.? PVVT by distinction can model variable/multispeed fan control at the terminal level, which may or may not reflect your actual equipment (depends on make/model). Fan control can also be made ?constant? in that regard if need be, as such this may be the most flexible solution. PSZ stands out from this trio as a zonal system type ? this fact may make it an easier system to consider in relation to a model or baseline you?ve already substantially developed with a zonal system type.
There is more than one right answer, and it?s worth noting/acknowledging VRF is fundamentally different in operation than any system type currently within eQuest.
Review of LG and Mitsubishi?s suggested practices / guidance shows some slight contradictions. Both notably prescribe system type PSZ, to start, but Mitsubishi explicitly mentions PVVT and PTAC as viable alternatives as well. Somewhere along the way I recall reading that energy recovery elements may be more easily accounted for with PSZ over PVVT? can?t recall the specific source. LG by has produced a library of (air-cooled) curves specifically for use with modeling variable speed compressors. Mitsubishi in contrast (perhaps, in response? also for air-cooled VRF) asserts it isn?t critical to explicitly model variable speed compressors to approximate VRF within eQuest, rather that the PLR/EIR/Capacity curves furnished by the manufacturer can, together, adequately address performance.
As I understand it, any chosen approach to VRF in eQuest involves ?post-processing? hourly reports to quantify and sum ?free? heating/cooling energies. There is some variance in guidance (between the energy trust of OR and Mitsubishi) on how to sum those free heating/cooling energies... both methods appear conservative to my understanding of how VRF works (summing each hour?s energies in isolation of the preceding hourly results), but then I am certainly no expert.
~Nick
????
NICK CATON, P.E.
Senior Engineer
360 Analytics
9750 3rd Ave NE, Suite 405
Seattle, WA 98115
office: 206.557.4732 ext. 205
www.360-Analytics.com
