Knob and Tube wiring

[powerplay]

When replacing an light fixture in a home with knob and tube wiring ( no bond ) Is it necessary to put it on an GFI breaker, or find a copper pipe to bond to before installing the new fixture? ..maybe a wrecking ball and new plans is the answer?

 

[Volta]

When replacing an light fixture in a home with knob and tube wiring ( no bond ) Is it necessary to put it on an GFI breaker, or find a copper pipe to bond to before installing the new fixture? ..maybe a wrecking ball and new plans is the answer?

Well, many new fixtures require 90? C supply wires, so if that's what is to be installed, you need to install a new branch circuit.

If you are simply concerned with the grounding and not the temperature, a gfci will help some, but 410.44 will direct you to 250.130(C).

 

[glene77is]

When replacing an light fixture in a home with knob and tube wiring ( no bond ) Is it necessary to put it on an GFI breaker, or find a copper pipe to bond to before installing the new fixture? ..maybe a wrecking ball and new plans is the answer?

To handle the temp requirements,
(1) Properly junction with the K&T in a junction box, above the ceiling,
(2) drop a Romex line down to a proper lite box for the lite.
I find that K&T frequently feeds directly to a lite fixture, hanging on a hook, without a junction box,
so that needs to be fixed.

So, are you feeding the K&T via circuit breakers, or
is the K&T on an old fuse box ?
Don't know of a GFCI Fuse Replacment Device :happysad:

Is the scope of the project to bring the circuits up-to-code ?
What is on your permit?

 

[Volta]

To handle the temp requirements,
(1) Properly junction with the K&T in a junction box, above the ceiling,
(2) drop a Romex line down to a proper lite box for the lite.
I find that K&T frequently feeds directly to a lite fixture, hanging on a hook, without a junction box,
so that needs to be fixed.

So, are you feeding the K&T via circuit breakers, or
is the K&T on an old fuse box ?
Don't know of a GFCI Fuse Replacment Device :happysad:

Is the scope of the project to bring the circuits up-to-code ?
What is on your permit?

Except that your J-box with the NM cable is now inaccessible 310.15.

And you still wouldn't have the ground required by 410.44, assuming the luminaire has exposed metal.

Of course you could splice as you are suggesting and extend the K+T with 90?C THHN per 394.10.

 

[tortuga]

Except that your J-box with the NM cable is now inaccessible 310.15.

Did you mean inaccessible 314.29? Is the attic Accessible? If it is this would be OK.

And you still wouldn't have the ground required by 410.44, assuming the luminaire has exposed metal.

Wouldn't he be in compliance with 410.44 Exception 3. IF he adds a GFCI device at the fuse box before the load, or add a GFCI breaker. You will never find a receptacle to replace with GFCI due to box fill and receptacles are usually all end of the run since splices are in walls.

Of course you could splice as you are suggesting and extend the K+T with 90?C THHN per 394.10.

Do you mean just THHN not NM-B?
I think bringing it into a box in the attic is the best bet if it is accessible. 394.56 prohibits inline if thats what you meant. Splicing to THHN not in a raceway sounds iffy however 394.2 states single insulated conductor, thats THHN. If you had to do that I would use singe conductor UF like they used to use to feed ceiling heating cables or at least #14 XHHW-2 copper. Most supply houses will not stock these. I suppose you could solder a western union splice to get around 394.56.
I have been known to apply heat shrink tubing to the type R conductor back to the first knob, then re sleeve it with the tubing. Heat shrink tubing is UL listed as 105 deg insulation. If you do not have enough conductor to enter a box that is a problem.

Most saw shops can carbide tip a 3-5/8 hole saw, combined with 1/2 of a basket ball to catch the dust you can cut the lathe and plaster to install a 3/0 cut in box.

If you work on old houses often see this report:
www.nfpa.org/assets/files/PDF/Research/RESAReport.pdf
Page 47 deals with fixtures with 90 deg wire on type R wire.
They list type R as 60 DEG insulation.
I have a old 1930 Grahm Renolds catalog that lists type R wire.
I thought it was 85 deg C rated.
I see more problems with 1980's 60 deg NM than knob and tube.

 

[Volta]

Did you mean inaccessible 314.29? Is the attic Accessible? If it is this would be OK.

Yes, that's what I meant. But Glene didn't mention an attic, he just said, "...Properly junction with the K&T in a junction box, above the ceiling... "

Wouldn't he be in compliance with 410.44 Exception 3. IF he adds a GFCI device at the fuse box before the load, or add a GFCI breaker. You will never find a receptacle to replace with GFCI due to box fill and receptacles are usually all end of the run since splices are in walls.

Yes, you're right. That would be compliant. But only to use the existing wiring, not to extend the circuit.

Do you mean just THHN not NM-B?

Yes, if we are talking about extending the circuit, IMO we cannot use NM-B, as any new enough to have a 90?C rating will also have an EGC. That EGC cannot be installed.

I think bringing it into a box in the attic is the best bet if it is accessible. 394.56 prohibits inline if thats what you meant.

I believe that 'inline' in that context is referring to a 'Western Union splice' without solder. Not a prohibition of a mechanically secure then soldered splice to extend the wire.

And I agree, that any splice that can reasonably be made accessible is better, but IMO not required for this application by 300.15. And I don't know that an accessible attic exists it this location, or if both of the K+T conductors would reach a box or boxes mounted there.

Splicing to THHN not in a raceway sounds iffy however 394.2 states single insulated conductor, thats THHN. If you had to do that I would use singe conductor UF like they used to use to feed ceiling heating cables or at least #14 XHHW-2 copper. Most supply houses will not stock these. I suppose you could solder a western union splice to get around 394.56.
I have been known to apply heat shrink tubing to the type R conductor back to the first knob, then re sleeve it with the tubing. Heat shrink tubing is UL listed as 105 deg insulation. If you do not have enough conductor to enter a box that is a problem.

Nice, that is the way to go. :thumbsup:

I carry both black and white ST in a couple sizes for old wires like these.

Most saw shops can carbide tip a 3-5/8 hole saw, combined with 1/2 of a basket ball to catch the dust you can cut the lathe and plaster to install a 3/0 cut in box.

If you work on old houses often see this report:
www.nfpa.org/assets/files/PDF/Research/RESAReport.pdf
Page 47 deals with fixtures with 90 deg wire on type R wire.
They list type R as 60 DEG insulation.
I have a old 1930 Grahm Renolds catalog that lists type R wire.
I thought it was 85 deg C rated.
I see more problems with 1980's 60 deg NM than knob and tube.

Yup, that's a good report.