Clarification on grounding at ceiling box


Old 11-17-05, 02:51 PM
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Clarification on grounding at ceiling box

I'm installing a new light fixture and bought a round plastic ceiling box. I noticed that inside the box on one side there is a small metal flange with a ground screw in it. This leads me to ask for clarification on how to connect the ground wires in the box? Should I connect a pigtail to this ground screw then wire nut the other end with the incoming ground wire and the ground from the light fixture? The thing I'm a little confused about is that I don't understand what purpose is served by a ground screw in a plastic box?? Would it be incorrect to simply connect the incoming ground to the fixture's ground wire?
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Old 11-17-05, 02:54 PM
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I have never seen a ground connection on a plastic box. Plastic boxes do not need to be grounded. The only thing I can come up with is that the connection can be used as a place to connect (and not use) the other ground wire if either the fixture or the incoming cable does not have one.
Old 11-17-05, 06:40 PM
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It is common for a ceiling box to have a metal clip as described. There is a green screw to connect the bare wire and also the ground lead from the fixture. If the fixture is all plastic, then it won't even have a ground lead. But if it has a green or bare wire, this is where it goes.
Old 11-17-05, 06:43 PM
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That screw is also the threaded lug for the crossbar to attach to. This way if an older fixture has no ground wire, and is metal, it will be grounded through the cross bar.

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