I have 4 prong dryer outlet that the previous owner wired up with 10 ga 3 conductor wire. He wired it "correctly" with a red, what, and black conductors. The ground terminal isn't connected to anything. I want to move it and add a ground. Would it be okay to run a separate green 10 gauge alongside this wire to get my ground?

  • ...are the wires run in a conduit? is the conduit metallic? If so, there's your ground.
    – Ecnerwal
    Jan 2, 2017 at 2:47
  • Can you post a photo of the inside of the box? Jan 2, 2017 at 12:31

1 Answer 1


Absolutely. You are allowed to retrofit a ground. In fact, NEC 2014 greatly softened the rules for retrofitting grounds (I believe this was legal before, but now there's no question.)

You can use green or bare wire, but if you use bare, use solid. It needs to be 10 AWG. The basic rules of laying the wire are the same as any other kind of cable. How often to fasten it, make splices inside junction boxes, etc.

Ground can follow any route back to the same panel the circuit is served out of. It can take any feasible route and does not need to run alongside the supply cable. (since current only flows momentarily during a fault condition).

It will suffice if you can reach a nearer junction box which has a 10 AWG or larger ground path back to that same panel, such as a water heater, range, air conditioning unit etc. Intact steel conduit counts as a rather thick ground wire. (Grounds can be shared because current only flows during a fault condition, and two circuits faulting at once isn't likely).

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