what size box?


Old 03-11-09, 11:33 AM
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what size box?


I'm planning to install a 220 circuit for a welder in a garage. The welder draws 21.7 amps and requires a 30-amp 2-pole breaker; I'll be doing a 10-12 foot run of 10-2 with ground to a 6-50R receptacle.

This will be an exposed "old work" installation and I plan to use a metal box for the receptacle and cover.

The receptacle I bought appears to be made to fit a 3.5 inch box. The cover appears to require a larger box unless I screw both the cover and the receptacle to the box with the same two screws. (sorry I can't think of a better way to describe that.) What is the recommended and minimum cu. inches for a metal box for this installation, please?

Thanks very much.

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Old 03-11-09, 12:12 PM
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I would use a 2 gang plastic nail on box. If you really want a metal box then use a 4"x4" square deep (2 1/8" I think) metal box and a 2 gang mud ring.

Other than an "in use cover" I have never seen a receptacle with a plate that you mount both at the same time using the same screws. Unless, you talking about an industrial steel cover with the screw holes on the corner. If so, you wire the device, mount the receptacle to the cover, then mount the cover to the box. If that is your cover then you will for sure need a 4"x4" square steel box.
Old 03-11-09, 12:56 PM
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If it's this kind of cover:

Mount the receptacle to the cover using the screws on the front, then mount the cover to a 4"x4"x2-1/8" square steel box using the screws in the corners.
Old 03-11-09, 02:51 PM
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Once again, y'all are a huge help.

That's the cover. I'll get a 4X4X2 and go with it.

Many thanks!


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