I am wiring a receptacle for a millermatic 251 welder that requires 48/42 amps. I am using 4 gauge wire for the two hots. Little overkill but it was gotten for free. I am not sure how to ground the 4-6 gauge wire I plan on using on the receptacle. The typical grounding screw meant to be screwed into the electrical box housing the receptacle is kind of small for accommodating 4-6 gauge wire, even when crimped with a end terminal ring.

The receptacle is housed in the electrical box which is all connected to the main panel via conduit, so I assume my grounding plan is up to code as conduit can act as a ground.

While using conduit as an equipment ground is allowed, using an equipment grounding conductor to supplement conduit is an industry standard.


You need to find the correct size machine thread screw and crimp terminal to connect the equipment ground to the metal box. If you need a larger diameter screw, drill and tap the metal box for that screw.

You can also use the 10-32 machine screw to mount a small lug for the ground wire.