I am looking for some notes on using a common ceiling opening to accomodate both attic fan and attic based air conditioner. Obviously there would need to be a controled damper device that would be deployed to vent attic fan air into the attic. It would need to close for use as air return through the condenser system. Does anyone have any experience with such a system?
Doyle
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Had never thought of that one before. I guess the way to do it would be to put a damper on the output side of the HVAC system that would dump the air into the attic. To go to attic fan mode you shut down heating/cooling and open the damper.
Of course, you'd want a damper that sealed really tight (few do) so that you wouldn't waste conditioned air into the attic.
Funny thing, I was assuming that I would re-use the existing attic fan system combined with the new AC ductwork but I see what you are suggesting...use the internal blower of the AC unit...duh. That would reduce the maintenance complexity somewhat. It might even be close to the same CFM, I don't know. Interesting. Thanks.
I'm not sure you'd be able to achieve the CFM of a mongo attic fan, but if the unit had a variable-speed fan you could probably come close. It would take some engineering of the controls, though, not something your typical residential HVAC guy can do.The other option, I suppose would be to stick a one-way passive damper into the side of the return air trunk, and feed that to a separate fan. Would be a hair simpler control-wise -- just turn off the HVAC, turn on the attic fan, and the damper would pop open from the force of air.
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I like that option. I think that might work quite well. Now I just need to make sure that all of the ductwork is appropriatly insulated for Kansas winters and summers.
Thanks