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Discussion Starter · #1 ·
First let me say that I'm asking this question as I really have no other options. I'm building an off-grid cabin in the woods and there is simply no electrician to hire.

So with that said, the cabin (more like a small house) will have a mini-split for AC and heating. Due to the size (16X24) I require an 18K BTU unit to adequately heat and cool. Of course all mini-split over 12K BTU are 240V (I bet you can see where this is going). Since all my current power options are 120V I want to use a transformer to run the mini-split. Here is where my knowledge lacks.

As I understand a mini-split requires "split phase" 240V with 2 hots (L1 and L2). However many of the consumer grade transformers on the market output straight 240V like in Europe (I think). Would a mini-split run on this straight 240V that is a hot and neutral? Or would I need to rewire the transformer in a different config (as I understand it, as an autotranformer).
 

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First let me say that I'm asking this question as I really have no other options. I'm building an off-grid cabin in the woods and there is simply no electrician to hire.

So with that said, the cabin (more like a small house) will have a mini-split for AC and heating. Due to the size (16X24) I require an 18K BTU unit to adequately heat and cool. Of course all mini-split over 12K BTU are 240V (I bet you can see where this is going). Since all my current power options are 120V I want to use a transformer to run the mini-split. Here is where my knowledge lacks.

As I understand a mini-split requires "split phase" 240V with 2 hots (L1 and L2). However many of the consumer grade transformers on the market output straight 240V like in Europe (I think). Would a mini-split run on this straight 240V that is a hot and neutral? Or would I need to rewire the transformer in a different config (as I understand it, as an autotranformer).
Yes it will run, but if it is a 10 amp load at 240v, Than the transformer will require and you will see a 20 amp load at 120 V so make sure you’re calculating your load properly.
 

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At 384 square feet, 1.5 tons of cooling is massively large, unless you have no insulation or are in a equatorial jungle. Around here, the quick and dirty calc is 2.5 BTU’s per cubic feet. At 3072 cubic feet (at 8 foot ceiling) here it would call for 7680, or 8000 BTU for cooling. And about twice that for heating.
 

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I can't really help you out here, that 220 stuff is above my pay grade,

But just wanted to say hi to a fellow DIYer !
Good luck with your project
 

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Discussion Starter · #5 ·
Yes it will run, but if it is a 10 amp load at 240v, Than the transformer will require and you will see a 20 amp load at 120 V so make sure you’re calculating your load properly.
Yup, I understand that. Its a MAX of 1700W in heating mode, so the 120V side should see no more than about 15A. A 3KVA unit should suffice (with double overhead). Thanks for the answer. I thought it would, but I really wanted to confirm it.
 

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Discussion Starter · #6 ·
At 384 square feet, 1.5 tons of cooling is massively large, unless you have no insulation or are in a equatorial jungle. Around here, the quick and dirty calc is 2.5 BTU’s per cubic feet. At 3072 cubic feet (at 8 foot ceiling) here it would call for 7680, or 8000 BTU for cooling. And about twice that for heating.
We have 22ft ceilings as its a lofted building. AC manufacturer sized things for me. They said I "might" be good with 12K, but on really hot days it would be marginal at best. On top of that, the 18K unit will heat in temps down to -30C where the 12K was only good to -15C.
 

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Discussion Starter · #7 · (Edited)
I can't really help you out here, that 220 stuff is above my pay grade,

But just wanted to say hi to a fellow DIYer !
Good luck with your project
Thanks fella.. Its been a fun project but way more work that I ever thought. Who knew trucking an entire house worth of stuff into the bush would be a lot of work!
 

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Would installing two units, both 120 volt, be impractical?

Perhaps one 12kW and the other make up the difference 6kW.

Use the 6kW as a supplimental if the 12 kW can't keep up.
 

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Would installing two units, both 120 volt, be impractical?

Perhaps one 12kW and the other make up the difference 6kW.

Use the 6kW as a supplimental if the 12 kW can't keep up.
Well if what traveler W above says is true, I’d go with the 240 W unit, especially if he’s “roughing it.” What brand if I may ask?
 

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