Run-Around Energy Recovery

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Have a project using a run-around loop to recovery sensible energy from laboratory exhaust fans. I have reviewed the archives and my own memory, but this is leaving me scratching my head. I also recall a recent (maybe?) discussion on Zone vs System exhaust that may directly feed into this - but cannot find it.

If the lab hood exhaust is put in at the zone level, eQuest won't do energy recovery on this air-stream, as zone exhaust goes 'outside', yes?

My current thought is to configure the VAV AHU to have either 'Sensible HX' or 'Heat Pipe' and also have self-contained ERV fans. I'd input the Exhaust fans in as scheduled and then put a low/0 power fan for supply since there really isn't such. The OA is moved by the primary supply fan. I'd also calculate a 'HX power' or the run-around pump. I'd have 0 zone exhaust; exhaust only at the System level.

Can anyone comment on this approach or advise on how to best approach?

Mechanical Engineer, Energy Analyst

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Daric Adair's picture
Joined: 2017-10-21
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I believe zonal exhaust can be captured in the relief airstream for ERV, but getting the relief airstream correct means getting a solid enough handle on everything else: return/supply/infiltration/exfiltration.

Following is the last diagram on this matter that I drew up for myself.

I'm open to comment/corrections, but this answers at least some of your questions, I believe:
[(AV3 ON) *Wi? 'Vr*ez -3d1*5m0 JM0d J9h?y3]

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Nick Caton, P.E., BEMP
Senior Energy Engineer
Regional Energy Engineering Manager
Energy and Sustainability Services
Schneider Electric

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M 785.410.3317
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E nicholas.caton at

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Nicholas.Caton at's picture
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