10,000 BTU window a/c not cooling bedroom

Old 06-26-13, 10:27 AM
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10,000 BTU window a/c not cooling bedroom

Hello! I am so glad I found this forum. This problem has been driving me crazy for over five years, but this year especially.

I live in a less than 500 sq/ft 3rd floor apartment in a 3-family. I have a 10,000 BTU window unit in my kitchen that cools the kitchen/living room area, probably about 300 sq/ft total (plus a small hallway and bathroom). I can have this set to 70 and within a half hour the area is cool and the a/c has gone into energy saving mode and shut itself off. FANTASTIC.

However, for years I had a 5,000 BTU window a/c in my bedroom which seemed to struggle to cool the room, so I finally bought a new one a few days ago assuming it was the aging a/c's fault. A brand new GE 8,000 BTU unit. However, it didn't seem to cool it to the same degree as my other rooms. It also felt slightly humid as well. Annoyed and assuming it was the a/c, I bought a 10,000 BTU Haier unit. Same result. It's set to 68 and never seems to cool to that temp, never goes into energy saving mode, feels slightly humid.

The room is about 20"x10" give or take, has four south facing windows, and the one east facing window (the unit is in this window). I've closed all the blinds and have tried it with the door closed and open. Nothing seems to change. Even at night when it's mid to low 70s outside.

I'm driving myself, and my boyfriend, nuts trying to figure out why this room won't cool like the rest of the apartment. What could it be?? I've searched this forum and didn't find a situation quite like mine, so any insight would be greatly appreciated.

Thanks guys!


Thanks for the answers thus far, however, this problem was happening even with a 5,000 BTU a/c.

Last edited by zootgirl; 06-26-13 at 12:32 PM.
Old 06-26-13, 11:36 AM
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You have probably installed an air conditioner that is way too big for the space. The temperature sensor is located just in front of the evaporator coil and therefore the signal it sends to the control board is a combination of the room temperature and the evaporator temperature. The machine runs, cools down the evaporator and then shuts off before the room itself cools.

Another possibility is that window air conditioners have the cool air discharge right above the room air inlet. The cool air comes out and immediately falls to the inlet where the temperature is sensed by that sensor in front of the evaporator coil. Because the unit runs such short cycles it never gets a chance to dehumidify the room air.

Using cardboard or the like try to baffle the out going cool air upwards towards the ceiling and also try to make a duct to cause the incoming air to be drawn from near the floor. Anything to keep the cool air from short-circuiting back to the inlet will help.
Old 06-26-13, 11:40 AM
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Yes, anything above 5000 btu is too large for a bedroom.

Either there's really major air leakage (nothing you can do about that) or the window unit is shutting down prematurely.

Try using a fan to push the cooled air away from the unit so it doesn't recirculate into the return as much.

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