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Im converting my garage into a small inlaw unit for my daughter I have a 125 amp service to my house. she will have a burner plate, fridge and an mini split ac unit for air and heat. it has a gas water tank. large tv and computer. the Main panel is out side our house about 30 feet from garage. there is not going to be laundry, unless you count the convienent laundry services provided by my wife in the main house!

  • Do you know how many amps or watts the mini-split will draw? – Machavity Jun 12 at 18:36
  • You should be able to get by with a 60 amp possibly a 50 amp feed to your panel, the size of the split can be a loose cannon here depending on the size but I would bet it will be a 30 amp max breaker size or smaller 220v unit (the last small single head I installed could have run on a 120v 20 amp circuit) but most have been 240v – Ed Beal Jun 12 at 18:38
  • its a 230vac 18kBTU – Will Jun 12 at 19:20
  • It say to use a 35 amp breaker – Will Jun 12 at 19:35
  • How many square feet is this unit, and will it have its own laundry facilities? – ThreePhaseEel Jun 12 at 22:30
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I would use a 30 space panel, because that is a cost sweet-spot between "Make sure you never run out of spaces" and "sanely priced". Electrical equipment is so cheap that there's no real economy in scrimping to the point of inconvenience. And believe me, you will want to upgrade things later, if not in the near term, in the far.

The panel does not need a shutoff switch if it's in the same building. Generally if a shutoff switch were required, people simply get a panel with a main breaker; it's cheaper, but nevermind that.

If the panel has a bus rating or main breaker, that does not matter (as long as it's equal or larger than the feed breaker). So don't be bashful about getting a 150A or 200A panel. The important thing is to get plenty of spaces.

I suggest a 60A cable feed and 60A breaker from the main panel. The cable to use is #6 copper or #4 aluminum. (Aluminum starts to make sense at these large sizes).

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