proper wiring of 2-wire light fixture

743 Views 7 Replies 3 Participants Last post by joed, Jun 22, 2020

brian85

Discussion Starter · Jun 18, 2020 (Edited)

I'm replacing the knob and tube wiring in my home, and if possible I'd like to re-use some of the light fixtures - not only to save money but also because of their old charm. I'm using plastic ceiling boxes like this: https://www.menards.com/main/electr...ing-box/b518ar-upc/p-1444444961757-c-6425.htm) I've read about wrapping the ground around a screw that holds the fixture up, but that seems sort of hokey? A few questions:
1) Is there a code-compliant way to wire a light fixture that only has 2 wires (ie no ground wire)? In other words, how to ground the light fixture? I realize that codes vary over time and place, but there might be a method that is very commonly accepted
2) Some of the fixtures don't seem as old yet they still don't have a ground connection. Do all modern lights have ground connections?
3) I'm a little confused by the importance of a metal box. If I were using a metal box, it sounds like (from my reading) that I could just connect the ground wire to the metal box and the fixture would be grounded. (Please correct me if I'm wrong!) Does that assume that there's a conductive connection between the fixture and the box? A lot of my fixtures have ceramic bases, so I was thinking that the connection between a metal box and the fixture might not be very good.
4) finally, the screw holes on many of the fixtures are wider than my very-standard box. Do they sell adapters for this issue? I've attached a picture of one such light fixture.

5) Is it crazy to re-install a light of that age?

thank you for your thoughts.

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daveb1

· #2 · Jun 18, 2020

The old wires of the light look a little sketchy in the picture. But if not too brittle could be reused. If you visit a lighting store rather than a big box, you will find lights with the vintage look you're seeking. But that will defeat you saving money , but could be offset by more energy efficient bulbs.

If you reuse the old lights, be certain that you determine which wire of the light is the neutral. The neutral should connect to the outer edge of the socket not the centre. The light will work if reversed but can be dangerous when changing bulbs while the power is connected.

A metal box would require a connection the the ground in your panel, but new cable will have a ground wire in it.

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joed

· #3 · Jun 18, 2020

That looks like a ceiling fixture and will likely be up high where no one could touch it easily. I would not be overly concerned about it not having ground wire.

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brian85

Discussion Starter · #4 · Jun 18, 2020

joed said:
That looks like a ceiling fixture and will likely be up high where no one could touch it easily. I would not be overly concerned about it not having ground wire.

This light hangs about 6.5 feed off of the ground and it has a pull string on/off switch.

Does the NEC distinguish between lights with reach vs those out of reach?

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joed

· #5 · Jun 18, 2020

Then I would be looking for a large ring terminal. You can crimp a ground into it. If you can find one large enough you can remove the lock nut that holds the chain to the hood, install the ring terminal and replace the lock nut.

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daveb1

· #6 · Jun 18, 2020

You'll need advise from someone better versed in code than I am. I would think code would be more concerned with having a switch by the door so you don't wander around in the dark looking for the pull string.

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brian85

Discussion Starter · #7 · Jun 22, 2020

joed said:
Then I would be looking for a large ring terminal. You can crimp a ground into it. If you can find one large enough you can remove the lock nut that holds the chain to the hood, install the ring terminal and replace the lock nut.
View attachment 603545

Thanks joed! What are the chain and hood? Are you referring to the chain that is pulled to switch the light?

If I understand you correctly, you're proposing that the ring go around the screw that holds the light fixture to the plastic electrical box? Do you know whether this is NEC-approved? Thanks!

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joed

· #8 · Jun 22, 2020

The hood is being held in your hand in the left pic. The chain goes from the hood to the bulb socket. The chain is held by some bits like this. If you remove the nut you can put a ring terminal on and replace the nut.

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proper wiring of 2-wire light fixture

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