Here is my problem I have a shed that is prewired with one receptacle and two lights that's 12 gauge and I was told that I could use 10 gauge wire coming into the shed in case I wanted to use large power tools coming from the circuit panel my question is is that ok.

  • 1
    You'd use #10 to reduce voltage drop. What's the length of the run to the shed? – isherwood Apr 22 '17 at 18:33
  • If you're asking about larger gauge wire to be able to use a larger amperage breaker (>20A), the answer is no unless you put in a sub-panel. – DoxyLover Apr 22 '17 at 22:32
  • These power tools plug into standard 15A or 20A receptacles, correct? – ThreePhaseEel Apr 22 '17 at 23:59
  • So what I'm hearing is if I put in a sub panel then I could use the #10 wire on the existng #14 wire already pre-wired in my shed. Also the length from my panel to my shed is 50 ft. – Tony Apr 23 '17 at 22:53

The 12 gauge wire in your shed is rated to handle a 20A circuit. This is sufficient for individual handheld power tools but can get overwhelmed if you are running dust collection at the same time or want to install several heavy duty tools (table saw, band saw, lathe).

Running 10 gauge wire means you could support a 30A circuit if you do as @DoxyLover suggested, put in a sub-panel. The 30A circuit would need to run entirely on 10 gauge or better wire. Not patch into the existing 12 gauge wire.

If you don't need 30A now it may still make sense to run 10 gauge wire. Depending on the distance of the run the voltage drop on 12 gauge could be substantial (search on "Voltage Drop Calculator"). Just keep in mind to install no more than a 20A breaker.

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