I am going to be putting a mini split in my finished attic. I will need a 12k model. They are available in both 115v vs 230v. The only difference I have found is that it might cost a little more to run the 115v as far as the cost of electricity. Thats not a huge concern to me because it is just going to be a guest bedroom. It would be easier for me to just run 115v to the unit so should I just go with 115v or is it worth it to run 230v? My gut says something that is going to pull that kind of power will be better to use 230v but I don’t want to waste my money on 230v if I don’t need to. Thoughts?
DIYorBust
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Messages 738 Reaction score 91 Points 28 Location Long Island, New York
I think the biggest advantage of the 230 is you’d be able to upgrade to a larger machine in the future if necessary. I’d also consider whether there is room in your breaker box for a double pole breaker. At the end of the day, the wire and breaker might cost a little more, but running the 240 circuit is not really too much more work, so you might try to negotiate with your electrician. Otherwise, if it’s just a simple project, and you know you’re never going to upgrade it, then go ahead and run the 120 and call it a day.
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dana
In the trades
Messages 7,889 Reaction score 509 Points 113 Location 01609
I am going to be putting a mini split in my finished attic. I will need a 12k model. They are available in both 115v vs 230v. The only difference I have found is that it might cost a little more to run the 115v as far as the cost of electricity. Thats not a huge concern to me because it is just going to be a guest bedroom. It would be easier for me to just run 115v to the unit so should I just go with 115v or is it worth it to run 230v? My gut says something that is going to pull that kind of power will be better to use 230v but I don’t want to waste my money on 230v if I don’t need to. Thoughts?
Why do you think it needs a 12K? Is the attic space completely uninsulated or something? Did you run a Manual-J load calc? In insulated houses with low-E double-pane windows the design cooling loads of most ložnice in Virginia would be under 8000 BTU/hr, even on the top floor. Even an insulated 400′ attic with crappy R19s in the head-banger cathedral ceiling, and R13 in the kneewalls and clear glass double panes is still likely to come in under 8000BTU/hr.
Many/most 12K mini-splits can deliver more than 12K of cooling at the AHRI test temperature of 95F outdoors. A cheap 12K mini-split might have a minimum modulated output that’s even above the DESIGN cooling load, and well above the průměr cooling load, which leads to lower comfort and poor latent load handling.
Try running a CoolCalc or LoadCalc on that attic zone, using aggressive (not conservative) assumptions on the air leakage, R-values, etc. It’s more comfortable to have a slightly undersized mini-split than a 2x oversized mini-split, and even those tools are going to overestimate reality by a double-digit percentage. I’ve seen LoadCalc overshoot by more than 25% on some rooms, even with conservative inputs, but it’s still WAY better than a WAG, or some idiotic «xxx feet per ton» rule of thumb.
As for the operating voltage it really doesn’t make much difference- only larger units would benefit much from 230VAC. Most 3/4 ton 115V minisplits can run on a 20A breaker, drawing less than 15A. eg, The 3/4 ton Gree Vireo draws 12A and calls out 20A overcurrent protection, the 1 ton Verio draws 17A, calling out 25A protection. Many 1 tonners might pull 20A and need a 25A or 30A breaker. eg The popular 115V Mr. Cool DIY 1-tonner calls out 20A wiring, 30A fuse. The peak amperage and breaker requirements are usually spelled out in the installation documentation somewhere- DON’T SKIMP on wire sizing, and don’t oversize the breaker.
