AC Butt Box is Sucking Air Out of Room

greytooth

Member
I have a 25000 BTU AC. The back end of it sticks out into a room that I don't want heated up, so I have a butt box built around it with a 10" hole in the top connected to about 3' of 10" insulated ducting connected to a 10" Can-Fan Max-Fan (1023 CFM) which to connected to the bottom of a disused swamp cooler.
I've discovered than when the fan is on it is not only sucking a lot of air through the vents on the back of the AC, but also a small amount from my room. (But enough that my CO2 tank is being drained too fast.)
My intent is to connect a Speedster control and (hopefully) find the sweet spot wherein the fan can still boost the AC exhaust but not suck out air.

Anyone have any general thoughts on this?
 
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