I took a no longer used 12/2 wire from our backyard and extended it to my new shed so I can wire lights and outlets. The wire is on a 20amp breaker in the main panel, which has 100amp service. My original thought was to install a small two breaker panel (70amp is the smallest I could find), and run lights off one breaker and outlets on the other. After researching online and watching some videos, I am questioning whether this is even possible. It would be nice to have them separate, but am I better off (or have to) running everything on one circuit?

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    If it's a 20 ampere breaker the wire should be 12 AWG, not 14. – Tester101 Oct 26 '14 at 19:20
  • Oops I misspoke, it is 12/2 – Dave Oct 27 '14 at 18:31

Since the feed from your main panel is on a 20 amp breaker and 20 amps is allowable for lighting and 120V outlet circuits, there's no reason to add a subpanel. The 20A breakers you'd put in the subpanel would be redundant. If you want a master switch in the shed, I'd suggest using a non-fused SPA/air-conditioning disconnect box. These are typically designed for two-leg 240V but you can just use one side.

All of the above assumes that you are in the USA and are keeping the circuit 120V and not 240V.

  • Also, If you want a master switch you could use a 20 amp single pole switch. – ArchonOSX Jun 18 '16 at 21:52

However, if you want to wire the shed with 14 AWG wire, then you will indeed need to protect this wiring with a 15A breaker, which would "waste" 25% of the 20A circuit capacity. In this case, installing a subpanel with two 15A breakers would be necessary. I would go with 12 AWG wiring…much easier and probably less expensive.

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