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econdave 06-21-2007 02:31 PM

A.C. Unit how big?
I guess I need to know how big of a unit to purchase for my bedroom, I am looking at a Sharp Window Unit, room is roughly 30x30x8.

bigMikeB 06-21-2007 04:45 PM

18,000 btu

sckeeth 06-22-2007 04:58 PM

I think that might be a little small. I would look more towards a 24000 btu unit. Generally you want one ton per 400 to 500 sq. ft. And it also depends on solar load, If that part of your house is in direct sun light all day I would go with the bigger unit, but if it's not go smaller.

bigMikeB 06-22-2007 07:32 PM

In this area it tends to be 600sqft per ton 400-500 cfm per ton. There are thousands of 1800sqft ranches with 3 tons that cool just fine. If you over size you will cool but never dehumidify (kind of like living in a meat locker). Two tons or 24,000 btu will do 1200sqft with average insulation. As we all know if you really want to be accurate and not use rule of thumb, do a heat gain calculation and get it size right but then again we were talking window units.

sckeeth 06-22-2007 07:47 PM

I agree my house is in Los Angeles I have a 3.5 ton unit and my house is 1300 sq ft.
I have full sun all day long, my house is 2 yrs. old. It works perfectly, it doesn't short cycle or run continuously. I also have a very dark roof almost black. So the rule of thumb I guess is different for your area.

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