Knob and Tube Connectors

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physis

physis

Senior Member
I'm interested in what everybody's using for connectors with K&T.

I don't know about anyone else, but I have a really hard time finding out what almost anything is "listed" for.

If I ask any of my supply guys if something is "listed" for whatever, the answer is either yes (is this EMT strap listed for securing plastic boxes? Uhh, yeah) or I'm not sure what you're even talking about. (At least that one's probably true)

So what are inspectors considering acceptable for terminating to a box?

Larry, Pierre, Romeo? (uh oh, a list, :D sorry for omitting anyone.)

[ January 18, 2006, 04:15 PM: Message edited by: physis ]
 
Re: Knob and Tube Connectors

Originally posted by physis:
I'm interested in what everybody's using for connectors with K&T.
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Ahh...Sam....ah...there is this new wiring method called NM, you might want to look into it.

It has a fancy bare wire in it and it comes in colors.
 
Re: Knob and Tube Connectors

Sam are you talking about K&T entering a box?

part of 314.17(B)
Metal Boxes and Conduit Bodies. Where metal boxes or conduit bodies are installed with open wiring or concealed knob-and-tube wiring, conductors shall enter through insulating bushings......
Click to expand...
 
Re: Knob and Tube Connectors

It's been a while since we've talked directly Bob, always a pleasure. Hope you've been well.

Anyway, back to the real world, :D , there are these buildings, some of them are older, that have this existing wiring meathod that sometimes has to be interfaced into 'newer" wiring that's been or is being added to what's already there.

You're killin me!! :D
 
Re: Knob and Tube Connectors

I'm looking for common practice and what's being done typically.
 
Re: Knob and Tube Connectors

I generally use an insulated bushing and run the K&T through it. Last time I did such a thing I pointed it out to an inspector, and he said that's pretty much the way to go.
 
Re: Knob and Tube Connectors

It's been a while, but this is how I do it. I use plain old NM connectors, cut a piece of the K&T loom, slide it over the K&T conductor, and then put the whole assembly into the rx connector, which is conveniently attached to a 4" square box. :cool:

Yes, I know, putting single conductor through a single knockout causes inductive heating.
 
Re: Knob and Tube Connectors

Originally posted by physis:
I'm interested in what everybody's using for connectors with K&T.
Click to expand...
Hey Sam,

Connector as in "splice" or as in "clamp"?
 
Re: Knob and Tube Connectors

Peter,

Good description.

Another variation is to use a gangable metal switch box with integral clamps inside (NOTE the "N" and "T" stamping inside the box by the clamp for genuine 100% listed K&T loom clamp certification).
 
Re: Knob and Tube Connectors

Originally posted by al hildenbrand:
Another variation is to use a gangable metal switch box with integral clamps inside (NOTE the "N" and "T" stamping inside the box by the clamp for genuine 100% listed K&T loom clamp certification).
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A good way to violate 300.20 :D
 
Re: Knob and Tube Connectors

Thanks Al. I have my doubts about the code compliance of my method, but it seems to be the preferred way in this area, as we still have tons of K&T alive and kicking.

I thought about a gangable switch box too with the N/T rating of the clamps. That would certainly be code compliant as long as a slot is cut in the box between the two knockouts.

Then there are those who simply "free air" the transition from K&T to NM cable with a few wire nuts. :roll:
 
Re: Knob and Tube Connectors

Originally posted by iwire:
Why not use a non-metallic box?
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Because I don't feel like it. :p Seriously, the last time I had to do this was about 8-9 years ago and I didn't know any better at the time, so I just always assumed it was ok. And I never learned either, until now. A non-metallic box would make a lot of sense.
 
Re: Knob and Tube Connectors

Originally posted by iwire:
A good way to violate 300.20 :D
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Not if I apply 300.20(B). That goes without saying in this OP about "connectors". ;)
 
Re: Knob and Tube Connectors

Year ago before nonmetallic boxes I would use a nm connector use a piece of loom used for Knob and Tube and bring the open wire into a 4"sq. box through separate ko's and bond that box to the egc from the new circuit. I still accept that system because It has never failed for me and i don't think there would be enough induction to create a heating problem on a 15amp circuit.

However there are duplex connectors and now nonmetallic boxes that would insure that it is a better method.

romeo
 
Re: Knob and Tube Connectors

Sam
Way out of my area. Irvine is way to new for this stuff to remain. Measning all the old k&t is gone now.

What exactly are you doing??

If your replacing an old switch box, then I would recommend a plastic box. Install the plastic box just like they installed the old porcelain one.

Finding new stuff listed for use w/ k&t even for replacement use would be like seeking the Holy Grail. ;)
 
Re: Knob and Tube Connectors

Originally posted by al hildenbrand:
(NOTE the "N" and "T" stamping inside the box by the clamp for genuine 100% listed K&T loom clamp certification).
Click to expand...
Nob and Tube? :eek:
 
Re: Knob and Tube Connectors

Originally posted by LarryFine:
Nob and Tube?
Click to expand...
:D

From the UL "White Book":
METALLIC OUTLET BOXES (QCIT)

Boxes may or may not be provided with clamps. When clamps are provided, the carton is marked to indicate the type of wiring system or combination of systems for which they have been tested. The clamps are marked with the following letters or combinations thereof to indicate that they are suitable for use with armored cable: ??A,?? flexible metal conduit ??F,?? nonmetallic sheathed cable ??N?? or flexible tubing (loom) ??T.?? Clamps that are suitable for type MC metal clad cable are marked ??MCI?? for metal clad interlocking armored cables, ??MCS?? for metal clad continuous smooth sheath cable, and ??MCC?? for metal clad continuous corrugated sheath cable. If suitable for all seven types, the clamp is marked ??ALL.?? Clamps suitable for nonmetallic sheathed cable are also suitable for multiconductor underground feeder and branch circuit cable where used in dry locations.

Clamps have been tested for securing only one cable per clamp, except multiple section clamps are considered suitable for securing one cable under each section of the clamp, each cable entering a separate knockout.
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In my experience, the "T" is always accompanied by a "N".

[ January 19, 2006, 12:19 AM: Message edited by: al hildenbrand ]
 
Re: Knob and Tube Connectors

If you have to make a splice with K & T my first method would be to use plastic 4" square boxes as Bob (Iwire) mentioned. If you have to use metal boxes I would use plastic U/F cable connectors (I believe Carlon makes them) to bring the conductors into the box. Make sure you re-identify which conductor is the neutral. It's usually hard to see conductor colors in an attic.
 
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