What type light box for knob and tube wiring

[Ravenvalor]

Hello fellow industry professionals,

I have a pair of knob and tube conductors poking out of a ceiling. Can I put 2 - ENT connectors on a pancake box and use it to hang a chandelier there? Article 394 mentions non metallic tubing. I can probably use a nonmetallic popin light box but I have not seen the job and am not sure if the wood ceiling can handle cutting. I am not a big fan of the telescopic fan braces.

Are there any restrictions as to what type fixtures I can install on K&T wiring insulation?

Thanks.

 

[Dennis Alwon]

Technically it is non compliant to add a new fixture to a K&T circuit unless you get a ground wire there. Have I done it? Yes, simply because the new fixture is more likely safer than the old one so......

A metal box would also not be allowed without grounding it. Given the ceiling is wood a pop in box may work depending on the weight of the fixture.

I don't understand why the ceiling would not be able to handle cutting.

 

[Steviechia2]

I agree with Dennis, even though it needs a ground I think it's safer to install a new light . I like to see a semi flush where there is no heat build up. I would try to use a plastic pancake box or plastic old work. Those knob and tube wires tend to get a little brittle and like to short out on metal boxes

 

[John120/240]

I second both above post. Adjustable fan hanger s are lifesavers IMO.

 

[jmellc]

I have done similar work by mounting a 2g plastic nail up box close to the K/T wires. 2g gives more space, less bending. If the K/T has any of the loom covering on it, use pieces of it to take each old wire into the box. Let 1/4" or more loom come into the box. If needed, staple wire near box, staple on the loom. If you don't have loom, a stacker near the box will work well, and heavily tape the wire at the entry point. If the wires are brittle at all, give them a layer of tape all the way. Take a piece of NM cable from the box to your light box. If the ceiling is too fragile to cut, use a plastic pancake box, as someone else said. A brown bakelite box is good if you can cut the ceiling. I bought a vibe saw recently and I find that it cuts fragile material with much less damage that a sawzall.

This way, no stress on the old conductors, clamping and hard twisting is confined to the new wire. If you get called back to replace the K/T, simply run new NM to your J box and not have to take the light down.

I just used this same setup to refeed K/T after a copper theft. Brought feeder to attic, fed J box & brought K/T into it.

 

[Ravenvalor]

K & t

K & t

Thanks for the replies everyone,

I will go look at the job armed with this new technology.

Thanks,

 

[LarryFine]

I've 'replaced' crumbling insulation in both K&T and BX installs by sliding on a length of insulation from modern NM. I remove as much of the crumbles as I can (it's usually only within the old fixture canopy's space or ceiling box.)

If the old wire is straight, I'll try the same size, but I usually end up sliding #12 insulation onto #14 wire. I cut it a tad longer than necessary so the splice and wirenut hold it snugly butted against the remaining old insulation end.

 

[mcclary's electrical]

I've 'replaced' crumbling insulation in both K&T and BX installs by sliding on a length of insulation from modern NM. I remove as much of the crumbles as I can (it's usually only within the old fixture canopy's space or ceiling box.)

If the old wire is straight, I'll try the same size, but I usually end up sliding #12 insulation onto #14 wire. I cut it a tad longer than necessary so the splice and wirenut hold it snugly butted against the remaining old insulation end.

Heat shrink works well also

 

[Buck Parrish]

Wasn't this changed in 05 or 08? I don't think the ground wire for lights is required if it's gfci protected.

 

[LarryFine]

Heat shrink works well also

Yeah, but my way is cheaper, easier, and 'cooler'.

 

[LarryFine]

Wasn't this changed in 05 or 08? I don't think the ground wire for lights is required if it's gfci protected.

I think we're operating under the "who's going to be able to touch the fixture and a grounded surface at the same time?" train of thought here.

 

[Ravenvalor]

I think we're operating under the "who's going to be able to touch the fixture and a grounded surface at the same time?" train of thought here.

Someone holding an aluminum step ladder for someone working on a fixture?

 

[Ravenvalor]

I've 'replaced' crumbling insulation in both K&T and BX installs by sliding on a length of insulation from modern NM. I remove as much of the crumbles as I can (it's usually only within the old fixture canopy's space or ceiling box.)

If the old wire is straight, I'll try the same size, but I usually end up sliding #12 insulation onto #14 wire. I cut it a tad longer than necessary so the splice and wirenut hold it snugly butted against the remaining old insulation end.

I hope it meets code because I like it.

 

[mtfallsmikey]

[I don't understand why the ceiling would not be able to handle cutting.[/QUOTE]


If it's real old-school hog's hair/plaster, it will crumble like the Roman Empire....

"Newer" plaster w/ wood/metal lath much more solid.

 

[Ravenvalor]

Mission Accomplished

Mission Accomplished

I went to the jobsite and there was the old style BX cable with boxes in the ceiling. The fixtures installed without a hitch. Once again, thanks for the help.

 

[LarryFine]

See? All that worrying for nothing.



The invoice is in the mail.

 

[jmellc]

I've 'replaced' crumbling insulation in both K&T and BX installs by sliding on a length of insulation from modern NM. I remove as much of the crumbles as I can (it's usually only within the old fixture canopy's space or ceiling box.)

If the old wire is straight, I'll try the same size, but I usually end up sliding #12 insulation onto #14 wire. I cut it a tad longer than necessary so the splice and wirenut hold it snugly butted against the remaining old insulation end.

I hadn't thought of that, I'll try it next time. I usually tape up.

 

[glene77is]

I've 'replaced' crumbling insulation in both K&T and BX installs by sliding on a length of insulation from modern NM. I remove as much of the crumbles as I can (it's usually only within the old fixture canopy's space or ceiling box.)

If the old wire is straight, I'll try the same size, but I usually end up sliding #12 insulation onto #14 wire. I cut it a tad longer than necessary so the splice and wirenut hold it snugly butted against the remaining old insulation end.

Larry,
Good technique, sliding new insulation over the #14.

I have used liquid rubber (liquid tape)
to paint cracking K&T insulation,
this holds (glues together) the pieces of K&T insulation.
Works on old 40's romex cabling and insulation.

IMO, there is no cure for old insulation,
only good techniques.