Heat recovery ventilationSubject: [Equest-users] Heat recovery ventilation

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Hi folks,
In double-checking the savings numbers from ventilation air heat recovery on my straight-forward VAV system, I noticed that the heating savings are less than half what I'd expect (based on back-of-the-envelope QC). I'm now out of ideas where to look for input errors, and am rather frustrated to see this happen on a pretty standard VAV system...

Would someone here have a moment and take a look, please (when running it, please use parametric run 4)? I'd appreciate any feedback.

Thanks much!!!

Peter Reppe, LEED AP, CPHC
Energy Analyst

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p. 541.342.7210
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Anonymous

Peter,
The model looks sound and I don't see any "oops" inputs so quick QC looks okay.
Several things are going on that can minimize the benefit of heat recovery:

- Oregon weather file with peak heating load at 34F

- Modest ventilation requirement with roughly 20% OA

- Low ventilation hours (2600 hrs/year)

- High (?) infiltration rate (0.7 ACH) representing 1/3 of your heating load for system sizing

- Efficient boiler

- BOILER: MIN-RATIO = 0; START-UP-TIME = 0; STANDBY-TIME = 0 which totally eliminates cycling and standby losses

Regards,
~Bill

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

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bbishop at pathfinder-ea.com www.pathfinder-ea.com

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