Hot Topics: Old Wiring

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Original Post: What to do about Old Wiring

rscholl - Member

I was just going to change a chandelier at my daughter's house and found this. It is cloth wiring? Whatever it is, it falls apart just from moving it.

The switch to the lighting wires is off, but there is also a junction in the box which I believe is still hot. The wires aren't copper, and appear to be metal or aluminum(?) and both have black casing.

I just need to know how to safely connect this—or should I just have her call an electrician? There's no access to the top, since it's on the first floor and the house is a Cape Cod built in the 1940s.

old rusted wiring with plastic caps

lambition - Member

That is cloth wrapping over rubber insulation.

You can fix insulation with electrical tape or heat shrink tubing (better option). Wires outside of the junction box will be fine so long as they are not disturbed.

Conductor on this type of wire will be tinned copper.

rscholl - Thread Starter

That brings me to the next question. The new light will have a black and a white wire. Will it matter which one I connect to since the supply wires in the box are both black?

lambition - Member

It does matter for safety reasons. You'll have to figure out which is neutral (white) and which is hot (black).

Since you have a cable feeding another junction box, you'll find a bundle what wasn't tied to the old light. This is your hot line feeding another junction box. Do not disturb it unless you see damaged insulation. If you disturb it, you may damage the insulation.

A bundle that was attached to the old light will be your neutral. (connects to white wire)

A single wire that was attached to the old light will be your switched hot. (connects to black wire)

If you don't remember which is which, easiest way is with non-contact tester, although some disapprove of them.

Put your non-contact tester on the wire in question with its switch on and then off. The wire that beeps with the switch on and doesn't with the switch off will be your switched hot.

A bundle that shows hot all the time will be hot line feeding another junction box, and the remaining bundle will be neutral.

Geochurchi - Member

Hi, I would definitely use heat shrink on those conductors, trying to tape them may do more damage, if you have a meter test between the box and a conductor, the one that goes off/on with switch is the black.

rscholl - Thread Starter

That is some great information. Thanks. It didn't help that both wires from the old light were brown.

lambition - Member

"...test between the box and a conductor..."

Considering the age of wiring, it may not be grounded. Probably old BX cable without bonding wire.

Metal cladding may provide some ground, but cannot guaranty if there is no bonding wire. I learned this the hard way by replacing a light fixture in one of these. A mounting screw nicked the insulation on the hot wire and caused a short to the box. Instead of tripping the breaker, the wire and screw got glowing hot, then melted off. I was lucky it didn't burn entire wire off.

Poor grounding may be worse than no grounding.

rscholl - Thread Starter

Bad to Worse

This wiring is just too deteriorated for me to work with—we're calling an electrician. The neutral wire has no insulation left and the live connection (with red wire nut) show signs of exposed areas on the wires.

The heat shrinking as some suggested would have worked, but I think it would instantly destroy whatever is left of that cloth wrap since it's so brittle. There is no access to the top of the box from above, so I would think they'd have to pull the box down and try to find some good connections up top in order to run some new wire into the box.

Any suggestions at this point would be great since I think we're out of options as far as DIY.

a rusted old wiring fixture

Zorfdt - Forum Topic Moderator

Running a new cable to an overhead light isn't the easiest project, but with a couple small holes in the wall/ceiling, it's not too hard. That's probably the best solution to run a new cable from the switch to the ceiling box. And possibly from the light switch to the basement to clean up the whole setup.

It'll require a bit of drywall work afterwards, but having a nice clean new run is definitely the safest/best solution!

lambition - Member

If that cable is ungrounded, as I think it is, you have to replace entire circuit as you are not allowed to extend ungrounded circuit.

The electrician may consider metal cladding a good ground, but if it's not bonded, you may have the issues I explained in my earlier post.

If you have a plaster ceiling, then it may become much bigger project.

You can just remove remaining insulation off the wire and push heat shrink tubing as far as you can (Ideally into the metal cladding) and put some heat to shrink the tubing.

rscholl - Thread Starter

The wiring is not grounded. They just ran the ground wire from the old fixture up to the mounting bracket and screwed it on.

PJmax - Group Moderator

I feel for you there. That's in bad shape and almost impossible to fix without access from above. I recently did a job with six old cloth-covered BX's in one acorn box like you have there. If I didn't have access from above, there would have been some major rewiring needed.

You can cut back to get to better insulation but it will still crumble. Those wires are baked from years of heat from a light fixture below.

rscholl - Thread Starter

I'm not desperate yet, but what if I loosened the clamps and just tried to pull down some better wire to work with. It all depends if they left any slack in the wiring but it might be worth a shot.

ibpooks - Forum Topic Moderator

You could try, but don't get your hopes up. Any flex and disturbance will probably crumble the insulation. Wire of that age used natural rubber and an organic fibers like cotton or flax in the insulation. Once it dries out and deteriorates, it rots away and is just gone.

As Pete said, when you come across a job like this you know it's just going be chasing back and replacing wire runs until you find something good or hit the panel box.