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I bought a Utilitech motion-activated floodlight 0072837. The installation instructions tell me to match up the white, black, and green (ground) wires to the house. I don't see any ground wire coming out of this light fixure. How would I ground it?

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It looks like the fixture is plastic, so it's not likely you'll have to ground it. The fixture strap (the brass color metal bits in the bag below the fixture in the photo) should have a threaded hole, where a green grounding screw can thread in.

Install a grounding screw in the threaded hole of the fixture strap, and attach the house grounding conductor to it.

I'm guessing the instructions included with the fixture are boilerplate documents, and are included with a variety of models.

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  • Yes, the instructions were for two models, one of which is mine. I don't quite understand why if this light is plastic then you ground it with a screw on the mounting bracket. Last week, I installed a metal light fixture and it came with a green ground wire which I connected it to the ceiling's green wire with a twisty cap. I don't know the physics behind these two styles of grounding. – JoJo Dec 30 '14 at 3:56
  • @JoJo Plastic is not conductive, therefore you cannot be electrocuted by touching the fixture. With a metal fixture, if the ungrounded (hot) conductor shorts to the fixture, you could be electrocuted by touching it. The grounding conductor reduces the risk of electrocution, by giving the electricity a safe path to follow (not through you). – Tester101 Dec 30 '14 at 14:27
  • In the olden days no ground was required at the light fixture. This means there are still plenty of locations that simply do not have the ground wire. Nobody today would recommend or allow this, but for older homes you don't need it on a light. FYI Ground wires actually go to the same contact points as the white wires do in the electrical panel. If you feel you must have a ground attach it to the white wire if and only if it's not acting as the hot. White wires used for hot should be marked with tape or marker but not everyone does that. – John Peters Dec 30 '14 at 21:55
  • @JohnPeters That is terrible advice. If you connect the grounding conductor to the grounded (neutral) conductor, you've effectively made the grounding conductor a current carrying conductor. While the grounding and grounded conductors do meet at the service entrance, they are not the same and cannot be used interchangeably. – Tester101 Dec 31 '14 at 1:24
  • Kirchoff's voltage and current laws state that the sum of either voltage or current "around the loop" is zero. If there is no physical difference in the end point connection they effectively are the same point "in the circuit". Ground should always be at a Voltage potential of Zero. The only way this would not be true would be if there were ground issues. But that is not related to this question. I agree with you that NEC would not approve this but.... there's no real issue as you mentioned unless the ground isn't at zero. If it's not current would flow in neutral too. – John Peters Dec 31 '14 at 18:49

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