repairing old knob and tube

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sybrandy

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I have a situation where there is about an inch of bare wire along a wire. This is the old knob and tube type wiring where the hot and neutral run seperately. I have heard that there was a special tape that I could use. Can any one confirm this and if so, what is it called?
 
sybrandy said:
I have a situation where there is about an inch of bare wire along a wire. This is the old knob and tube type wiring where the hot and neutral run seperately. I have heard that there was a special tape that I could use. Can any one confirm this and if so, what is it called?
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I'd tape it up really well with regular electrical tape and call it a day.
 
I use super 88, never heard of a special tape. Could you get shrink tube over it, some times I might do this but most of the times I use tape.
 
sybrandy said:
I have heard that there was a special tape that I could use.
Click to expand...
Given that the Knob & Tube method is the only method that still permits splices that aren't enclosed in junction boxes, I made it a point to lay into truck stock a roll of rubber splicing tape. One such tape is 3M Scotch 23. It's thick, and a short length will fill out to the surface of the insulated conductor.

I don't use it often, but when I need it, its the best solution. One can use this for filling in around split-bolts, and similar situations.

3M 23 is the type of rubber filler tape that was originally used on the splices when first installed. Friction tape was then used to "harden" the re-insulated area. But, today, IMO, modern plastic tapes, such as 3M 33+, 88 or 22 do a better job of protecting the rubber splicing tape.

The only reason, IMO, to use the friction tape, such as a 3M 1755, is to "restore" an historic installation of Knob & Tube. One might do so for a museum, say.
 
al hildenbrand said:
Given that the Knob & Tube method is the only method that still permits splices that aren't enclosed in junction boxes, I made it a point to lay into truck stock a roll of rubber splicing tape. One such tape is 3M Scotch 23. It's thick, and a short length will fill out to the surface of the insulated conductor.

I don't use it often, but when I need it, its the best solution. One can use this for filling in around split-bolts, and similar situations.

3M 23 is the type of rubber filler tape that was originally used on the splices when first installed. Friction tape was then used to "harden" the re-insulated area. But, today, IMO, modern plastic tapes, such as 3M 33+, 88 or 22 do a better job of protecting the rubber splicing tape.

The only reason, IMO, to use the friction tape, such as a 3M 1755, is to "restore" an historic installation of Knob & Tube. One might do so for a museum, say.
Click to expand...

I agree Al, good advise! I saved the ends of the friction tape roles and rewound them backwards for the close in splices when covering the Servets in a gutter with the rubber tape first, then with the friction tape.

If the problem is with the K&T insulation that is dried out, and crumbles like a pretzel that would be another reason to look for more open bare wire.

By the way see 394.56 for K&T splices and taps. :smile:
 
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