Can I splice wires in an old ceiling light box and should I add a ground conductor?

Question

We have a beautiful house built in the 1920s. I was changing over a light fixture when I found that the ceiling of the room is wired with rubber wrapped 12(?)gauge wire that goes into a metal pancake box attached to what I believe is a ceiling joist. Based on current code I think it's overfilled as it has one pass through common wire (that goes in and out without any termination), the common line, and 2 load wires that are spliced together (I'm not sure why there are 2 loads). The visible insulation appears to be in good condition. If I'm just changing a fixture I know I'm not required to make this code compliant.

My understanding with the reason for the code is excess heat causing damage to the conductors leading to insulation failure --> fire. The fixture is a chandelier that will be 3 feet lower with LED bulbs so heat and wattage should be much better than it ever was before.

My questions are:

1. Can I cut the pass through wire and wire-nut it? I figure yes but I wanted to make sure.

2. The box covering the ceiling has ample room to leave wires in it, to my mind that would be safer from a heat standpoint. I don't know if that's code compliant or stupid for a reason I'm not aware of.

3. Replacing the pancake is possibly doable but I'd then have to cut into the wood rafter to make room. I'd prefer not to do that out of concern for opening up a can of worms. I'm wondering if I need to replace the box.

4. Current wiring does not have a ground line. If I attach a ground to the metal box does that provide any safety gain?

Thanks for your help. Elmo

Answer 1

On this site there have been discussions from knowledgeable people about the importance of having every hot and its paired neutral conductor in the same cable or conduit. This is so the net time varying magnetic fields surrounding the wires are zero and so will not induce currents in surrounding metal. Induced currents cause heating of the metal.

I think you should find out what this pass through wire is being used for. This seems like a situation requiring a current clamp meter to find out the current (including the direction) in each wire under load. You may really need an expert electrician to look at this.

Answer 2

Well, that's a first I've seen and I've seen a lot...but a pancake box with NO 8/32 side threads?

Looks like the original original fixture was hung from the center all-thread and was actually probably fed by gas, not electricity. At some point, it was converted over. But all that is speculative and I digress.

I see no point in adding a ground and changing the box out as long as the fixture is secured properly. I'd first remove the center all-thread if possible, then use long wood screws to grab into the ceiling joist to secure the chandelier.

If you really had to yank the box out and replace with new wiring, then best to replace the entire circuit, switches and all. Little more work there. The new box could be a inch 1/2 deep and 3"or 4" diameter and needs to be rated for the weight of the chandelier.

Edit: Regarding the unbroken loop. My gut feeling is the electrician who wired the light was, and how to say this politely, going over and beyond. A unbroken loop is more reliable. Heck, its even crossed my mind to do it in my practice, but it's just not realistic. But again, I digress. In the box is a one 3 wire with extra conductor cut off to save space which gives the impression of a 2 wire. In situations like this the 3 wire provides a continuous hot or neutral at the other junction. No worries.