We're changing the extremely old fixtures in our hallway with some sleek modern LED lighting.

Upon removing the fixture I discovered three sets of twisted wires - double white, black-red (the fixture used it for the black) and a black-white pair that wasn't connected to anything. The electrical box itself is grounded (I think - there's a bare copper wire tied to a screw in the electrical box) but the new fixture says to attach the green fixture ground wire to the "power supply ground wire" which, as far as I can tell, doesn't exist.

The previous fixture had a bracket with a grounding screw but that bracket is incompatible with the new fixture, which came with it's own plate/bracket system (but nowhere to put a grounding screw).

How do I properly ground the fixture? Would the untouched black-white pair possibly be a part of the solution?

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    Where does that bare wire come from? One of the cables? If so, that should be your power supply ground wire. – bib Jun 15 '16 at 19:33
  • @bib that bare wire is just a stub - it's so short and the box is so crowded I'm not sure, but it looks like it came out of the white pair. There's literally no way to stretch that to connect to the fixture ground. Do I need to cut another wire to connect the two? – Isaac Kotlicky Jun 15 '16 at 19:36
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    Post some pics please, a few good ones will say more than mountains of paragraphs ever could. – ratchet freak Jun 15 '16 at 20:45
  • Add a 6" or 8" piece of copper to the box screw and now you have your ground, Sometimes a fork connector crimped on to the wire is easier to add or another grounding screw in the box. – Ed Beal Jun 15 '16 at 23:09
  • @EdBeal I ended up cutting the grounding wire out of the old fixture and attaching it to the bare wire/screw combo, then connecting that with electrical tape and a wire connector to the fixture ground. Annoying as hell to rig but it did the trick... I'll probably have to repeat that for the other fixture... – Isaac Kotlicky Jun 16 '16 at 2:24

If the box is grounded, look around for a hole in the box that's tapped for a 10-32 screw. It may be on a little "hill" and already have a screw in it. Attaching a solid-core wire to this, or a wire with a spade or ring terminal, is the right way to "grab" ground off the box. I like ring terminals, they're a little harder to work with, but you can put more than one on a screw.

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