Heat Pump Size for 224 Sq. Ft. Sunroom

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Old 07-16-10, 02:44 PM
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Heat Pump Size for 224 Sq. Ft. Sunroom

I'm going to enclose the porch at my lake home (Lake of the Ozarks, in Central Misourri). It faces the lake (Southwest), and is 32' long by 7' wide, with an 8' ceiling.

I'll have 2 X 6 walls, with 8 - 42" X 60" windows (vinyl sliders - low E & Argon, probably builders grade Jeld Wen or similar) along the lake side. Both ends will have sliding patio doors, so it will be almost all windows on three sides. It's quite sunny, so there will be direct sunlight on the windows.

I'll insulate the ceiling and sidewalls with fiberglass batt insulation. The roof of this porch is the upstairs deck, which is waterproof. I'll finish the ceiling, probably with aluminum soffit material.

I'm planning on heating & A/C with a through-wall heat pump (with an built in electric heating element for when it's too cold for the heat pump). I'll install the unit below a window in the center of the long wall, and I'll have a couple of ceiling fans in the room to help circulate air.

Temps in the summer frequently exceed 90 degrees, and will often hit 100. Winter temps are typically between 30 and 50, although it will occaisionally get colder. Although we won't necessarily run the heat / air all the time, we'll want to be able to use it when we choose to, even in the extremes.

I'm pretty sure it will harder to cool this room than keep it warm, due to the sun exposure. Any ideas what I need for capacity?
 
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Old 07-16-10, 03:45 PM
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Best to run on the freebie heat-loss and heat-gain calculations. You can Google those terms plus things like A/C sizing, furnace sizing, etc.
 
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Old 07-16-10, 04:50 PM
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Yeah, I've done that. It comes out to about 11,000 BTU's. That seems high to me - I saw the other thread about a similar size room, and it seemed he was having trouble with his with that large a unit.

Thanks for the response. I'd be happy to hear if anyone has any other ideas.
 
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Old 07-16-10, 06:42 PM
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For a room...let's say a bedroom or hotel room, about that size, normal amount of glass, insulated walls and ceiling, then 7 or 8 thousand would be about right. Given all your glass, 11 would not be out of the question.

You might want to have a reasonable heat load calc. done, because as you suggested, too much oversize will short cycle and not do a good job.
 
 

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