Wiring new range

11 years ago

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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Comments (4)

weedmeister
11 years ago
Ask on the Electrical Forum.
live_wire_oak
11 years ago
You cannot adapt an existing 3 wire circuit. You are required to run an entirely new circuit from the box with 4 wires.
odo53
Original Author
11 years ago
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?
kaseki
11 years ago
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.

kas