Wiring new range

odo53May 8, 2012

I want to update the range outlet from an older style 3 prong (10-50R) surface mount box to an inwall 4 prong (14-50R) for my new range. The new range is tighter to the wall so the inwall connection makes better use of space. The existing cable is non-metal sheathed 3 conductor 8 awg with a 10 awg ground. I have put in a double gang metal box for the outlet and run the cable into it with proper clamping.

What is the required grounding procedure for the metal gang box? I have 14 awg grounding pigtails and I have the special green #10 screws for 20 amp, 120V service but this seems inadequate compared to the 8 awg wires that are carrying current in. What is the required wire gauge for grounding the box? How do I attach that cable to the box? Can I use the pre-threaded hole with a #10 screw?

Thanks much!

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Ask on the Electrical Forum.

    Bookmark   May 8, 2012 at 6:05PM
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You cannot adapt an existing 3 wire circuit. You are required to run an entirely new circuit from the box with 4 wires.

    Bookmark   May 9, 2012 at 12:07AM
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Thanks live_wire_oak. Agree that you can't simply convert a 3 wire installation to a 4 wire, but the existing cable I have has 4 wires, 3 x 8 awg plus a 10 awg ground. The old install didn't use the separate dedicated equipment ground but it is grounded at the main breaker panel. Seems OK to me. Am I overlooking something?

    Bookmark   May 9, 2012 at 9:16PM
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The 10 AWG ground wire should be connected to 10 AWG grounding conductors from the box and from the receptacle. This is within the capacity of "blue" wire nuts, or a U bolt clamp. You can of course go larger.

The cable is attached to the box using an appropriate connector. The connector looks like a 12/2WG NM (Romex) connector on steroids.

The no. 10 screw should be adequate. Use a no.10 Yellow crimp fork connector or just wrap a solid conductor wire around the screw. Ground faults usually last only moments until the breaker actuates.


    Bookmark   May 10, 2012 at 10:37AM
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