I'm running the wire to my garage. Wanting to run a 220 air compressor And couple 110 outlets and lights. Is it possible to run 10/3 or do I need
Like 10/4. For that extra hot. I'm running from breaker box to junction them off to 12/2 for my 110s. Imma framer not an electrician. Thanks

  • What will you be running at the same time as the compressor? – Harper - Reinstate Monica Apr 30 '19 at 21:54
  • Is your garage attached to the house, or detached (i.e. its own structure)? – ThreePhaseEel Apr 30 '19 at 22:15

Put a sub-panel in the garage, not a junction box. If you join 12/2 wires to the circuit, you CANNOT have more than a 20 amp breaker feeding them. If you put in a sub-panel with breakers, the 20 amp limit comes into play after the sub--panel breakers, and the feed from the main is sized for the wires feeding the sub-panel. Go bigger than you think you'll need, you won't regret it later, as most people that put in a tiny one eventually do. The sub-panel can be a "main" type panel (and could be 100 Amps, even if only fed with 30, 40, or 50 Amps), you just need to remove the ground to neutral bond. 10/3 (which has 4 wires, including the ground) would be adequate IF you are only looking for 30 amps capacity. But you actually should get individual wires and...

Put conduit in the ground, not direct burial cable. Trenches are expensive (in money or labor) conduit is cheap (in less wire damage, and the ability to replace wires later without digging again.) You need 4 wires (hot, hot, neutral and ground) and you should really consider all future uses when choosing the size of wire, rather than picking the smallest possible size. Doing it once is cheaper than doing it over.

You need to define your loads - compressors come in many sizes. The plate on the motor should give amps as well as volts; though starting them is often a bit more demanding than the running rating those provide (sometimes there is additional data on the plate which may help with starting load or required breaker size, sometimes not.) If we go minimal and assume your lighting circuit is 15 Amps at 120VAC and your tool circuit is 20 Amps at 120VAC, you're riding the hairy edge if your compressor needs more than a 10 Amp at 240VAC breaker with a 30 Amp feed, and it kicks on while your 120 tools are going. Might want to go to #8 copper or #6 aluminum for your conductors and kick up to 40Amps - default recommendation around here is actually 50A for a typical garage shop. At least choose conduit big enough to allow for that later...

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  • I fully agree with ecnerwal, I had 1 customer that had me put in a tiny panel, I suggested a 100 amp panel that only cost about 20$ more, he went cheap, a few years later he called me back, I made the same recommendation, he went cheap again, after that he wanted a charger for his new car, finally we installed the 100a panel, if he would have followed my advice the first time we would have put in conduit and wire large enough for his current needs but he wanted UF (direct bury), go big on the panel, and put conduit in At least 1" but 1-1/2" would provide more than enough room to up size wire.+ – Ed Beal May 1 '19 at 15:40

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