K&T in light fixture

[sfav8r]

This may be true but I couldn't find a code reference. An inspector just told us that knob & tube wiring can't enter any light (in this case a can light) because the wire must be 90 degree rated. I wasn't there personally so I couldn't ask for the reference. Any ideas?

What type of wire the old K&T anyway?

Thanks.

 

[pete m.]

The requirement for the insulation temperature rating will most likely be found on the fixture labeling. The wiring used to supply the fixture will need to meet that temperature rating or it could be considered a violation of 110.3(b).

As far as the K&T insulation temp rating I'm not 100% sure but I would wager that it's not 90 degrees.

Pete

 

[ike5547]

I believe it's treated as 60 deg. in S.F.

 

[sfav8r]

These were 5" can lights. The wire actually feeds the j-box on the side of the can then the socket in the can is fed via mc cable. T j-box is part of the fixture so I assume the NEC makes no distinction.

 

[al hildenbrand]

The manufacturer's instructions for the temp rating of the supply conductors to the jbox on that 5" recessed light will probably call out 90?C.

I haven't gone out and looked at the labeling on my stock. . .but that's what I recall.

 

[peter d]

You will have to box the K&T and splice some NM-B cable onto it, and then enter the j-box on the recessed light.

The intense heat generated by the recessed light will quickly degrade the K&T insulation otherwise.

 

[macmikeman]

This may not fly past your inspector, but in his book called "Old Electrical Wiring" (a pretty good one at that) author David Shapiro details a possible way to work it out by using higher temperature rated heat shrink tubing to go around the knob and tube conductor insulation. Even the author states that it is only a suggested posibility and that it would be best to get the inspectors blessing before trying to do it that way. Another possible but not very attractive solution is installing a close by j box and jumping a new nm-b out to the recess can. Grounding the can will become another whole can of worms to deal with.

 

[e57]

Splice on some THHN.... But then you need to have a ground - which might lead you back to the main panel....

 

[George Stolz]

Read 410.18 for the requirements (and exceptions) to grounding light fixtures.

 

[Bea]

Thanks
George I was looking for that the other day.

 

[sparky_magoo]

Read 410.18 for the requirements (and exceptions) to grounding light fixtures.

Talk the HO into a service upgrade with GFCI breakers.

 

[sfav8r]

Read 410.18 for the requirements (and exceptions) to grounding light fixtures.

Doesn't that refer to EXPOSED lighting? Would a recessed can that will have plastic trim be considered "exposed?"

The Article 100 definition refers to "indavertantly" touching. It seems unlikely that someone would indavertantly touch the fixture that is 8' in the air. On the other hand, if you consider replacing a lamp I suppose you could indavertantly touch the metal housing..of course you could indavertantly touch the socket also.

 

[Rich Elec.]

Hey sfav8r,
If you have a lot of questions about K&T, macmiekman listed a good reference to chek out. I also own the "Old house wiring book," it is very informative.

 

[e57]

Talk the HO into a service upgrade with GFCI breakers.

In the '02 code you can't extend lighting without a ground. Apparently the '05 either?

Exception: Replacement luminaires (fixtures) shall be permitted to connect an equipment grounding conductor from the outlet in compliance with 250.130(C). The luminaire (fixture) shall then be grounded in accordance wtih 410.18(A).
Commentary: The exception to 410.18(B) provides a method by which a luminaire with exposed conductive parts can be installed at an outlet where the wiring method is not an equipment grounding conductor per 250.118 or does not provide an equipment grounding conductor. In older installations where luminaires are replaced, the requirement to ground exposed metal parts of the luminaire is not negated simply because there is no means of grounding provided by the existing wiring system. The means allowed by the exception is the same as is permitted for receptacles installed at outlets where no grounding means exists. A single grounding conductor can be run independently of the circuit conductors, from the outlet to a point on the wiring system where an effective grounding connection can be made. The acceptable termination points for this separate grounding conductor are specified by 250.130(C).

 

[sfav8r]

Hey sfav8r,
If you have a lot of questions about K&T, macmiekman listed a good reference to chek out. I also own the "Old house wiring book," it is very informative.

I found it at the library today. It looks very interesting. Not sure how much it will help with code questions, but it looks like a good source.

Thanks to macmiekman

 

[George Stolz]

If we were to go by the open text of 410.18 only, then the can wouldn't have to be grounded, arguably. But 250.96(A) requires the metal enclosure of the can to be bonded:

250.96 (A) General. Metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, fittings, and other metal non?current-carrying parts that are to serve as grounding conductors, with or without the use of supplementary equipment grounding conductors, shall be effectively bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them. Any nonconductive paint, enamel, or similar coating shall be removed at threads, contact points, and contact surfaces or be connected by means of fittings designed so as to make such removal unnecessary.

Much like the AFCI requirement, this would not be retroactive - if you swap a receptacle in a bedroom, the receptacle outlet never changed, so AFCI is not required to be added. If you add a receptacle in a bedroom, that receptacle's circuit is required to be AFCI protected.

I'd say that if we were looking to add a recessed can to an existing circuit, the new enclosure would have to be bonded to an EGC per 250.96. It makes no issue about "exposed" metal parts, and has no relief for adding to old work.

I submitted a proposal to allow branch circuit extensions to make use of the GFCI relief in 406.3(D) - it was rejected on the grounds that new equipment needed to be installed per today's code. In this case, the enclosure of a new can would require an EGC be installed.

I think the text in 410.18 is confusing, and should be revised in the 2011 cycle to more directly address old work.

 

[sfav8r]

You will have to box the K&T and splice some NM-B cable onto it, and then enter the j-box on the recessed light.

The intense heat generated by the recessed light will quickly degrade the K&T insulation otherwise.

I'm not sure I agree on that one. Many original fixtures served by K&T were were flush mounted with two or three lamps. They generated a lot of heat and the outlet was directly above the fixture. On the Juno, Elco, and Halo fixtures, the j-box is 4-5" away from the fixture which has a double wall for IC rating. I'd wager that the temperature in that j-box is considerably cooler than the original fixture.

 

[peter d]

I'm not sure I agree on that one. Many original fixtures served by K&T were were flush mounted with two or three lamps. .

But you still can't feed a recessed light with anything less than 90C wire. So the K&T is out of the question to feed directly into the light on the j-box.

And of course I'm sure you've seen what kind of condition the old wire is in when it's been cooked by a surface mounted light. I once used up almost a complete roll of tape on one j-box that had multiple old BX cables with rubber/cloth insulation that had completely disintegrated when I took the old light down.

 

[LarryFine]

I once used up almost a complete roll of tape on one j-box that had multiple old BX cables with rubber/cloth insulation that had completely disintegrated when I took the old light down.

Next time, consider sliding THHN insulation over the wires instead. You can side it inside the sheath as far as the old insulation falls off, and then strip the ends to suit. If the same-size insulation is too tight, go up one size.

 

[chris kennedy]

The manufacturer's instructions for the temp rating of the supply conductors to the jbox on that 5" recessed light will probably call out 90?C.

I see that 90C supply rating all the time. So using NM in recessed fixtures is a violation of 334.80?