Help on Basement MiniSplit sizing.

5 years ago

Hi,

I received some quotes on Minisplits and the sizing is very inconsistent so hoping to get some help on sizing. Attached is the layout of the area.

- Its 650 square feet in the basement with about 83 feet of perimeter wall exposed.

- I live in North Pennsylvania.

- The basement ceilings are 7 ft and the walls are mostly subgrade.

- I have insulated the wall with 2.5 inch thick Foam and the floor is unisulated, upstairs is a heated area.

- The coldest is gets in the basement with no heat is 45-47 degrees in the winter.

- There are 2 windows and 1 door to the outside.

I am not sure I am doing the heat loss calculations correctly. Any help or guidance on sizing is appreciated.

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Comments (6)

sktn77a
5 years ago
Basement heating/cooling loads are usually less on a sq ft basis than above ground spaces. A 9,000-12,000 BTU unit should meet your needs. Is the basement dry?
Michael C
Original Author
5 years ago
The basement is about 60-65% humidity in winter and 80% in summer. I run a dehumidifier in the summer and it controls it well.

I was originally estimating a 12k wall unit but 2 of the 4 quotes I got came back with 15k units. It's my only source of heat in that area.
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mike_home
5 years ago
I am surprised that your basement gets down to 45 degrees in the winter given it is 4-6 below ground. Is this due to leaky windows and door? The 12K size should be sufficient, but it some models the smallest size may be 15K. You should get all the model numbers of what is being proposed and do your own research. The equipment price difference is about $200 - $300. You probably will not need to use it in the summer for cooling.

A 80% humidity level in the summer is very high. Do you get water condensation on the cold water pipes?
Michael C
Original Author
5 years ago
Good point, the 45 degrees was before I gutted it this summer so it should be much better this winter. It had old windows and an old door, also little to no insulation. I replaced everything and insulated the walls/rim joists. So that should have a good impact.

If I don't run humidifier I get condensation but I run one all summer and don't have issues.

I am comparing the multizone units of the LG/Mitsubishi/Fujitsu. One unit will be upstairs and one in the basement. Going up to the 15k model downstairs makes my outdoor unit jump up to the next level and quotes jump another $2k-$3k. This is the reason I am trying to determine if the 12k will be sufficient. Thanks.
mike_home
5 years ago
If it was a few hundred dollars, then I would have said you would be fine installing the 15K BTU size. Spending another $2K-$3K for an additional 3,000 BTUs of heating is not necessary. Now that you have insulated and replaced the windows and doors, the heating load will be lower. Some of the heat supplied by the electric baseboard is going the keep the main room warm.
sktn77a
5 years ago
I'd just be careful not to oversize the unit. Humidity is going to be a major issue in the summer and an oversized unit won't dehumidify well.