# Cogito Ergo Plenum (Plenum Question).



## BlowerMotor (Sep 21, 2021)

Good evening and thanks in advance for indulging an HVAC amateur. 

My question is pretty basic and I'm probably overthinking this, but does anyone see any potential issues with what I'm proposing in my diagram below? I'm wanting to take out about 12' of return flex line that runs through my crawlspace and connects to the plenum, and instead simply create a new plenum between the HVAC unit and the exterior wall of the house. This would probably be a 2.5 ton packaged unit (electric heat and air). The supply duct already runs up vertically from the unit in its own little enclosure on the side of the house and turns 90 degrees into the attic. 

I would of course insulate the plenum very well and also have a cover connecting from the exterior wall of the house on each side of the unit. The only issues that I can really foresee might be related to the air temperature in the plenum, the fact that is would be drawing air from the bedroom only, and possibly some whistling from the filter/plenum. The reason that I'm doing this is that my house is a piece of junk and the crawlspace is about 15" at its highest point - the return flex line was just lying in the mud and spelled like a dead elephant.


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## beenthere (May 30, 2009)

Sorry, we're a tradesmen only site.

Please use our sister site DIYCHATROOM.COM, thank you.

Thread closed.


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