I am modeling a laboratory air handler system with 100% OA, ERV at the air handler and a separate laboratory exhaust fan. I modeled the laboratory exhaust fan as zonal exhaust and thought I would only get energy recovery from the remaining exhaust at the air handler but this is not the case, as described previously below and as I confirmed using a custom hourly report.
How then to model energy recovery only for the central exhaust and not the zonal exhaust?
The one thing that comes to mind is to derate the design ERV effectiveness based on the % exhaust that returns to the ERV. The figure below (from Trane?s Ronnie Moffitt, in the ASHRAE Handbook S26.11) shows the reduction in energy recovery as a function of bypassed exhaust.
~Bill
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William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer
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