I will be running power to detached studio that is about 50ft from my home. The studio will have 6 canned lights, 1 chandelier, 2 porch lights, and 6 receptacles. The studio will also have a 115v mini split AC that pulls 10.4 amps. My plan is to have a sub panel with two 20 amp breakers. One breaker would feed the circuit for lights and outlets and one would feed power to AC with disconnect outside. Can I use a 30 amp breaker to feed from my main panel with 10/3 wire or do I need a 40 amp breaker with 8/3?

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    It depends an awful lot on what else you plan to plug into those receptacles. With 10/3 you don't have much breathing room for expansion, so for instance if you want to add a PC and laser printer, or table saw and dust collector, you'll be in trouble! Also, subpanels are dirt cheap and please consider one with lots of space, e.g. I would fit nothing less than a 20-space panel, and you'll want one with a "main breaker" so it provides the requisite shut-off switch. – Harper - Reinstate Monica May 30 '17 at 17:40
  • Really depends what type of studio yours is, and what you want to plug into the 6 recepts. For example, my friend calls his photography studio a studio, but he also has quite a bit of computer load and a lot of speciaty high powered (not LED) lighting for photo shoots. – Tyson May 30 '17 at 17:44
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    We probably need a little more information. First when you talk about 10/3 or 8/3 to an electrician. It usually means you are using a 10/3 cable with a ground and the ground is never counted as a conductor. So are referring to 10/2 cable and running just a 120V or a 10/3 and running 240V? Second are you sure you are installing a 10.4A 115V split AC? I am not saying you don't have one I have just never seen one. Most 115V AC's are window units and are fractional ton units. – Retired Master Electrician May 30 '17 at 18:01
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    @Tyson that's a good point, it might matter what else OP plans to plug into those receptacles. You're right, I don't think s/he has much breathing room with 10/3, cable isn't cheap but trenching is worse. – Harper - Reinstate Monica May 30 '17 at 18:10
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    @Harper Yup, $50 or $100 more in materials now is nothing compared to starting from scratch again when it gets cold because he forgot the plasma tv is 10 amps, the computer etc is 4, and the two space heaters are another 20 combined, and there's a potters wheel with a 3/4 hp motor 🤣 – Tyson May 30 '17 at 18:43

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