Non-Metallic box for light fixture crossbar needs grounding?

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Dennis Alwon said:
Read my previous posts
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I read what you said. You claimed that the little screw recess in the box effectively insulates the screw head. I don't see how it does anything of the sort if a wire nut comes loose. The end of the wire can go anywhere.

One of the problems I have always had with the term "likely" is that the code uses it but never defines it in some useful way.
 
petersonra said:
I read what you said. You claimed that the little screw recess in the box effectively insulates the screw head. I don't see how it does anything of the sort if a wire nut comes loose. The end of the wire can go anywhere.

One of the problems I have always had with the term "likely" is that the code uses it but never defines it in some useful way.
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Of course it can but the nec appears to accept the recess as a safe bet.
 
petersonra said:
how would you go about bonding the metal screws?

in any case, the mounting bracket is on the outside of the box.
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The bracket in the OP is inside of the box and is for mounting a fixture to the box. One of these types:
cross_bars-fixture_mounting_crossbars1.jpg
 
We talked about this here before. They do make a plastic fixture box with a ground screw that is part of a metallic insert that the fixture screws thread into. I think it was Code in some jurisdiction to use them for fixtures.

-Hal
 
If there are metal screws that protrude into the plastic box then that is an issue. The ones I have seen have the screws recessed as shown in the picture for the switch box... same idea but for a round box.

raco-boxes-brackets-7825-64_1000.jpg
 
Dennis Alwon said:
Of course it can but the nec appears to accept the recess as a safe bet.
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I don't think the NEC is worried about an internal box mounting screw becoming energized. However, it is concerned about energizing a mounting bracket that could be contacted by a person, such as a luminaire canopy.
 
Do the 8/32's typically used to mount the fixture to the strap provide a bonding means? Why would the crossbar need a different size egc from the fixture they are part of the listed fixture.
 
eds said:
Do the 8/32's typically used to mount the fixture to the strap provide a bonding means? Why would the crossbar need a different size egc from the fixture they are part of the listed fixture.
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Consider a steel box because plastic boxes are relatively recent. The mounting bracket, hence the fixture, was always bonded to the steel box by virtue of the screws and direct contact. Now along comes non-metallic boxes. The mounting bracket still needs to be bonded so the fixture manufacturer provides a green bonding screw on the bracket with the assumption that the installer would either provide an EGC pigtail or extend the EGC from inside the box to the screw. But because that isn't always going to be followed especially by homeowners and DIYs, some jurisdictions wanted the same assurance that a steel box provides and that is what that fixture box that Dennis posted a picture of does.

-Hal
 
If I were to use the non metallic box like Dennis posted, then I would not have to make up the fixture egc to the branch circuit egc. (for sake of discussion). I still feel that the 8/32's will provide a bonding means with the box posted or with a standard fiberglass box and metal strap.
 
eds said:
If I were to use the non metallic box like Dennis posted, then I would not have to make up the fixture egc to the branch circuit egc. (for sake of discussion). I still feel that the 8/32's will provide a bonding means with the box posted or with a standard fiberglass box and metal strap.
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If you use the box that Dennis posted the brach circuit EGC would go to the green screw and the EGC from the fixture would go to the green screw on the fixture bar. They do not need to be spliced together.
 
I understand that concept, I guess my logic is on a standard plastic or fiberglass box with out the ground strap. The fixture strap will be bonded to the egc via the 8/32's used to attach the fixture to the strap.
 
eds said:
I understand that concept, I guess my logic is on a standard plastic or fiberglass box with out the ground strap. The fixture strap will be bonded to the egc via the 8/32's used to attach the fixture to the strap.
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So you're saying that you're relying on the fixture to bond the strap?
 
eds said:
yes
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That's a violation. As Dennis stated the EGC must connect to the bar.
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250.148(B) Grounding Continuity. The arrangement of grounding connections shall be such that the disconnection or the
removal of a receptacle, luminaire, or other device fed from the box does not interfere with or interrupt the grounding continuity.
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