Brittle Wire Insulation

Elshupacabra

The light fixture in my kitchen needs to be replaced and when I took it down I discovered that the set up has three cables coming into the box that are tied together and has two wires coming down to the fixture. The problem is that the insulation on some of the wires is brittle and falling off, exposing the bare wire.

I'm curious as to what the correct course of action is here safety and code wise do I just cut back the wires and open the cable and piggyback extensions on there? or is there an alternative method that I'm not aware of?

The home was built in the 70's and has the basic two wire 120v cable

Yoyizit

There is a glass mesh tubular braid slip-on wire insulation that appliance part stores sell.
An electrician on this forum came up with the idea.

Jupe Blue

There are a number of ways to address this. NEC states that there need to be 6 inches of conductor inside the box outlet to be a legal installation. That being said, in my area it is very common to find houses built in the 60's & 70's that have very short wires in the box.

If you have access above the ceiling, pull the wires into the accessible space , cut them back until you find pliable insulation, set some j-boxes and refeed the light using the same size wire.

If you don't have access, you can use heat shrink tubing rated for the correct voltage in your application. Just slide it over the bare conductors and apply your heat gun. You can even but splice wires on to increase the length and shrink tube all of it.

ScottR

You should turn the circuit to that fixture off in the mean time, or at the very least cover the bare wire with electrical tape temporarily (electrical tape is not a permanent fix!) and leave the switch to the fixture off. (There may still be power to the box even with the light switch in the off position).

You could do that (though the word "piggyback" brings some bad images to mind), but any connection you'd make between the old wiring and new wiring would have to occur inside of a junction box. And that box would have to be accessible (meaning in your ceiling, with a cover over it).

If your wiring isn't too old (30-40 years isn't so bad), it shouldn't be deteriorating like that, but it depends on the type of insulation. It could be that the lighting fixture was overheating (for example if you had a 100W bulb in a fixture rated for 60W). If that's the case, things aren't so dire.

How comfortable are you with electrical work? If you're uncertain doing it yourself, this may be a good time to call in a pro..

Some questions:

Are the 2 wires in a plastic sheath, or do you have BX (armored cable)?

Just to confirm, you don't see a bare or green ground in the box?

Is the wiring copper, or aluminum?

Can you post a picture of the inside of the box?

joed

Heat shrink tubing. You slip it over the wire and then heat it up and it shrinks tight to the wire. Make sure it has a high insulation rating.

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Elshupacabra

Yep, that's the first thing I did.


I know, that's mostly why I posted this thread. I know I could redo it and get it to work, but it might not be the safest or even easiest way.

Like I said, the home was built in the late 60's early-mid 70's and I've done other electrical work in the house, even in the kitchen installing GFCI outlets and this is the first time I've ran into this problem. The fixture is old, probably like the one that came with the house old. It's rated for 75watts or lower and it had two 75's in it when I took it down. But it's very possible that it got warm up there once or twice over the years.

I'm pretty confident in my ability. I've done a fair amount of work in the past, but I'm hoping that it won't go deep enough to have to call a pro


Full Size Picture

You can see the three cables coming in there and all the grounds tied together. You can also see some of the insulation chipped away on the black wire that is in the bottom left of the picture and that is the wire that used to go down to the fixture. Also, I know that the box is broken on the side there and I planned on replacing it when I climbed up to do the wire work.

Scuba_Dave

Do you have access from above or is the 2nd floor finished?

Elshupacabra

I have access through the attic.

Scuba_Dave

You could then put a junction box in the attic & do away with the "bad" wire

spark plug

What I'm surprised about is that a house built in the '70s has brittle insulation. We deal on a daily basis with house wiring that is at least 70 Years old. Most of the wiring and insulation is delicate (should be handled with the skills of a Brain surgeon) but functional. As Scott has pointed out, there must have been excessive or unvented heat above the light fixture, that prematurely destroyed the insulation!

ScottR

Heheh.. good to know. Without knowing your level of skill it's hard to know if you mean 2-wire [+G] or just 2 wires. Wanted to make sure we're on the same page. (BTW - Like my tag says, I'm just a DIY'r, not an electrician, so some of the other guys may have better advice..)

Yeah, definitely replace the old box and secure the cables properly. If you use a metal box, then also connect it to the grounds using an approved bonding screw. (Not sure if the bond screw on the fixture's bracket, if it exists, would meet the requirement.. hmm..)

The black conductor in the lower-left: you said that was wired to the fixture -- it's hard to tell, but it comes out of the "romex" (or whatever brand of NM) in the lower-left, outside of the pic? If the sheath of that cable is stripped outside of the box, that has to be fixed too. IIRC you need 1/4" - 1/2" of a cable's sheath extending into a box.

Because of that, you can't just re-insulate the conductor.

If you have some slack on that cable, you could pull it into the jbox so that you can cut away the damaged wire/insulation, re-strip, reconnect and you're done.

[Woops, just wrote another paragraph and then realized you said that the attic is right above there].

From above, you can just cut the damaged wire back a bit (1 ft, 3 ft, whatever). Run that old wire into a new jbox, and run new NM-B from the new jbox to the fixture's box. Connect black-black, white-white, gnd-gnd-box in the new box, and you're back to normal.

Oh, and from the looks of it that's a switch leg (?) and the white conductor is hot too -- if so the conductor should be marked with a color other than green anywhere it's visible in a box (using a sharpie or electrical tape).

BTW - I'm not old enough to remember those crimp-style wire connections. I assume they had plastic covers and looked like wire nuts before you started messing around?

Elshupacabra

Yes, that black wire comes right out of the cable.

I'm not too familiar with the names for wiring configurations really, but I'll test them before I start ripping them apart and see what's what.
No, actually this is exactly how I found it, minus the e-tape that I wrapped around the wires. I've seen similar crimped copper cuffs around other parts of the house too and you can still buy them!

Yeah, I'm surprised too. Like I said earlier, I've torn apart other parts of the house and all the rest of the wires were fine. You can tell in the picture that the insulation is right up against the box (something else I'll fix while I'm up there). Maybe that has something to do with it? I have no idea.

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So, it sounds like cutting back the cable to a point and feeding into a J-box above with some new NB and a new fixture box is probably the safest, best way to go. Thanks for everyone's input! Very helpful!

joed

That is the best solution. And it will not prohibit you from using fixtures requiring 60ºC wiring if you feed the box with NM-B.

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ScottR

That's only if he replaces all 3 cables with NM-B going to the box, not just the damaged one. (Did you mean prohibiting from using >60deg. fixtures? My head might be in the clouds today..)