Minisplit Sizing for Basement
Looking for the experts to lend a hand. I’m installing a minisplit in my basement and trying to determine which Mitsubishi unit will best meet my needs. My location is Halifax, NS, Canada. My main concern is re: square footage, but I’ve included a few other questions as well.
The two options are:
I attempted to do a manual J calculation and determined my heating BTU needs at 5F are 9200 btu/hr for 585 square feet.
One question I have is the basement consists of a main rec room, bathroom, bedroom, mechanical room, and storage closet. Should I be including the last 4 in the square footage? Only some of them?
The mechanical room and storage closet doors are always shut while the bedroom and bathroom doors are always open so I only included the bedroom and bathroom, but if I should have added in the mechanical room and closet then I think the FH12NA is the only option as the additional square footage will increase the btu’s. I’ve made a rough attempt to draw the layout and the red circles indicate where I’m considering putting the minisplit (only one of the red circles will be used). Also there is a stairwell that leads up to the main floor that I factored into the square footage. There is no door at the bottom of the stairs, but there is at the top.
The max output for the MSZ-GL12NA at 5F is 10200 btu/hr while the MSZ-FH12NA is 14000 btu/hr.
Even if I’ve used the proper square footage, another consideration is the defrost cycle. In another post I read to estimate a worst case reduction of 5-10% of hourly btu’s to allow for defrost and assuming 10%, the GL12 is almost exactly 9200 btu’s at 5F. Would that be fine?
In the event it matters, the minimum 48F rating of the GL is 2000 btu and the FH is 3700. At 40F (typical daytime temps in the winter) my needs would be 3900 btu. At 48F it would be 2900 btu’s (less than the FH), however, I am less concerned about the warmer temps because I suspect I will turn the minisplit off at that point. I believe the FH would not cycle on/off at 40F given the basement requires more than the minimum of the unit, but please advise if you believe otherwise. There are minimal windows in the basement so there would be next to no solar gain.
Appreciate any help I can get.
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