2 to 3 prong outlets older home

johnc777February 15, 2014

Kind of a generic technical question. The usual answer is to use a GFCI and the little tag. Are there any situations where a regular 3 prong outlet can be used?

I'm thinking about house with metal conduit. How about flexible metal? AC would be ok but old true BX no? How about Romex with the small ground wire?


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Ron Natalie

A properly installed metal conduit can be the ground. If you install it right, you can install a grounded receptacle using the ground from the conduit.

The armor of old BX is not a sufficient ground. Neither is current type MC (though it will typically have a grounding conductor other than the armor). Type AC's armor (and it's integral bonding strip) can be used as a ground.

Type NM (ROMEX) with a ground wire is OK. Most of the smaller stuff (12, 14) has a full size ground (it's just bare). Larger stuff has a smaller grounding conductor because such is an acceptable size.

Art. 250.130(C) allows the extension of a ungrounded branch circuit to be connected to certain grounds to pick up the equipment ground.

    Bookmark   February 15, 2014 at 3:15PM
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