Ok, my house was built in ’43. The wiring is cloth covered with some black plastic insulation over the copper. The cloth is ok, but the insulation is very decayed-it just crumbles when the wire is bent. I pulled a couple of wires out of a ceiling box and put them into a new metallic junction box. When I folded the wires back into the box, I notice that they had cracked and raw copper was exposed. I pulled them back out, wrapped them with tape and very carefully folded them back in. The breaker held so I though I was done. So…I was working on the affore mentioned ceiling box. My new junction box was in the way so I reached up to push it back. I was greated with a shower of sparks. I pulled the cover off the box and found one of the wires had grounded right at the box’s strain relief. It actually burned the wire off. In order to reconnect the wires, I’ll need to make them longer. The problem is that there isn’t enough slack in the run to do this without actually splicing another section in. And I still havn’t dealt with the problem of the crummy insulation! I really don’t want to put two junction boxes in because it looks like chit and I can not pull out the old bx because it’s in a finished wall! So….what do I do?
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Duh, wait til 4Lorn replies!
I would suggest you either fork over the big bucks for somebody else to do it or do further DIY education and rewire everything. Suggestion, get yourself a fish tape and a 5 foot drill bit <G>
Last month I added a 3 way switch to my Mom's house that has K&T built in 1908. Happily, nothing I needed to splice into or reroute cracked, and was able to feel confident I would not have to take another week off normal job and rewire and fish 1/2 the whole house. (Never considered re-wiring it before as Pop had just died in Jan. and he definetely decided these matters on his house - he had rewired the other half in the 50's, but decided then that what was left was OK, even better than the 'modern' ROMEX -- he was right as always.)
A suggestion - if you choose a rewire, use as much conduit (PVC OK) as you can if you plan on living where you are for more than 40 more years due to insurance cutoffs for "rewire" deductions.
Unfortunately sounds like you have little choices, splice box being the cheapest. Usually if you can move a little further down the wire where the insulation is still covered in plastic the insulation should be in better shape.
If you do not want to go to the expense of a rewire I have had sucess repairing old wire with heat shrink..... but think of it as a bandaid solution until it can be more permantly.
bake
Whatever you do, just ask yourself one question: "Will I be able to sleep at night?"
That, to me anyway, dictates how I do my electrical.
Forget about trying to repair what you have. I had the same thing in my 1928 house, and just had to bite the bullet. On the up side, it gave me a chance at plastering, since I had to patch all the holes I made in each stud bay to pull BX through.
Replacing one 3-way switch turned into: Pulling up the T&G flooring in an unfinished walkup attic, removing 80 year old FG insulation, running all new wiring to switches and outlets (which also let me add some much-needed outlets), putting in new insulation, and putting back the T&G boards, most of which split somewhat during removal, and I'll probably have to put plywood over that. This project has only taken me since last Spring, and it's still going. Summer came and it got too hot in the attic. Then winter and holidays, too busy. Did get some insulation down when it got REAL cold here. Boards are still in a heap, waiting for my return.
Do it right, and sleep well.
Pete Duffy, Handyman
Well, I can sleep tonight, because the breaker is still off. lol. It looks like I'll be opening up the wall. :(
Pretty common problem with no really simple answers.
The first question is is the deterioration just in the ceiling box and its immediate vicinity or is it more wide spread?
Early wires were insulated with common latex rubber. At first it wasn't even vulcanized so it remained soft. Vulcanizing the rubber caused the sulfur impregnated rubber to attack the copper conductors. Had a few fires before manufacturers learned to tin, coat with tin/lead solder , the conductors to prevent this problem. Sometimes these wires cause confusion as they look vaguely like aluminum.
The vulcanized rubber was better but over time it still dries up, gets brittle and falls off. Heat and ozone case it to deteriorate even faster. This is the reason behind knob and tube, K&T, wiring. It was not dependant on the original insulation. Even after the rubber gives up air and porcelain knobs and tubes, thus the name, keep things from shorting out. End history of insulation 101.
If the issue is within the box replacing old insulation with heat shrink tubing works well. If you can maintain clearances heatshrink can reinsulate the wires in a K&T system back to the closest knobs. Hemp or cotton loom, used to act as a jacket to provide physical protect each wire going into separate holes in the box, is largely unavailable. The glass fiber high temperature and plastic automotive stuff is nowhere near as good.
As always check with the authority having jurisdiction, AHJ on methods. I have used friction tape, a cotton tape impregnated with asphaltum, that can take a lot of friction. Bulldog is a popular brand. Even high quality plastic tape can't handle this type of abuse.
Next worse case is if the dried insulation is limited to within 6" of the box. This is not uncommon with ceiling fixtures. Incandescent lights generate a lot of heat. Worse if the HO used bulbs larger than what the fixture was designed for.
If this was early romex and there is some access you might get lucky and be able to find some slack to get the jacket, the material that surrounds both, there if you have a ground, into the box. Sometimes I can get my arm up into a ceiling and carefully loosen a staple without rearing up the cable. Great when it works out.
Failing to get the jacket into the box, or in the case of K&T mounting a box and running new cable is the way to go. If I have attic access and the jacket is within an inch or so some jurisdictions will allow you to replace the missing jacket with layers of friction tape. Four layers laid on neatly and run an inch into the box is good.
No major problem if you have access to the back of the box, as with an attic. You can mount a box in the attic and run new cables. All connections must be in a box with a cover. Failing any access it becomes a matter of tracking the cable, wires in the case of K&T, back to the next accessible point and replacing the run/s. Blind fishing cables.
If your system is run in conduit this sort of thing gets easy. Use one of the old wires to pull in the new. Simplicity. Conduit systems trade increased installation costs versus for lowered repair costs and increased protection.
I think you're right. This was a ceiling light fixture and I'd bet that the heat advanced the decay of the insulation. Luckly, this is the only ceiling fixture in the whole house.
If the space above the ceiling is truly inaccessible and you don't mind the aesthetic hit you could install a old work box some distance away from the existing ceiling box.
Mostly useful if the system is run with romex, NM, this can simplify and speed a repair. It can help with some K&T issues but it tends to get fiddly, finiky and murphoid as you are working through a small hole while standing on a ladder and doing a delicate job. It reminds me of building a ship in a bottle.
A 5' jump, watch the direction of the joists, is usually easy to do through the hole cot for an old work round box. You cut the hole and can get an arm in. Arlington, and a few other manufacturers, make a screwless blank plate for round boxes that actually looks good, is textured, and almost disappears with the next coat paint.
Well, it's been two evening and I'm still working on it. Man, has this ever turned in a cluster...mess. Yes, the wires were only baked in the box. Unfortunately, there is absolutely zero slack in the line that broke. You see, the ceiling box was mounted tight to a metal duct. When the duct was installed, the bx was pushed down tight to the ceiling. The bx ran between the ceiling and the duct before it dipped down the wall to a bedroom outlet. I figured the outlet was the end of the line, until I realized that the attic and some exterior lights were dead too. The problem was that there was only one cable coming out of the ceiling box! I went to the bedroom and pulled the box apart. Luckily it was a remodelers box so I could get it out of the wall. There were two lengths of bx and 1 romex line going to/out of the box. Luckily the 2 bx's had a different profile so I was able to identify the correct one in the attic (after pulling up the floor). I taped a new length of romex to the dead bx line and tried to pull it up. Because of the duct laying on the cable, I wasn't able to pull the wire. I went back down stairs and carefully measured where the wire penetrated the top plate. I punched a hole in the wall and found the cable. I was able to work a staple loose. I went back to the box and was able to work another staple loose. I figure that if nothing else, I'd be able to pull the wire down (not knowing how'd I get the new romex line in). I was literally standing on the wire and it would not move! Talk about super staples! I went back up to the hole at the top plate and cut the bx off. I still couldn't pull it out-but I was able to pull the wires only leaving the casing. The wires looked really good. Naturally. I went back up to the attic and the cable slid right out with very little effort. It was that doggone staple holding the wire some where in the middle of the wall. I now needed to feed power back to the outlet. The other piece of bx the came out of the outlet went to a junction box up in the attic. I figured that if I could refeed the junction box that I could then reverse the flow on the existing piece of bx and use it too fee the outlet. As of last night I got the power fed to the junction box and the cover plate back on. I only need to make the connection from the existing supply to the ceiling fixture (remember that problem?) to the new romex. Oh, yea. I still need to turn the breaker on! lol!
Yes, keep in mind that your problem may very well be limited to this ceiling fixture. Even when the proper sized bulbs are used, ceiling fixtures tend to bake the wires and turn the insulation brittle. Install an oversized bulb (100w instead of 60w is quite common) and the problem becomes that much worse.
It usually isn't necessary to rip out the entire ceiling to replace a wire. With some cleverness and a lot of cursing you can usually limit the damage to a few small areas.