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#37884 - 05/10/04 01:30 PM Knob and Tube Wiring  
wiremann-54270  Offline
Junior Member
Joined: Jan 2004
Posts: 9
Lebanon, PA USA
I have to enclose some open air splices in knob and tube wiring that ties to romex.
I will be going to look at it tomorrow, but I need some ideas how to get the old stuff into a j-box. Usually k and t is ripped out and replaced, but these people are selling and do not want to spend much.


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#37885 - 05/10/04 02:17 PM Re: Knob and Tube Wiring  
HotLine1  Offline

Joined: Apr 2002
Posts: 6,853
Brick, NJ USA
Each conductor must enter through an individual KO, and be protected by a non-conductive sleeve and the sleeve should be clamped/secured to the box.

Some people use a grommet in a 1/2" KO, as the 'sleeving', more than likely is unavailable.

Speak to your local AHJ for his/her take on this method.



#37886 - 05/10/04 07:05 PM Re: Knob and Tube Wiring  
Electric Eagle  Offline
Joined: Apr 2002
Posts: 914
Alpharetta, GA
I haven't seen the splices, but if they are original to the wiring, I think they are safer if left alone. I personally would refuse the job if the customer wouldn't allow a rewire of the circuit. Make sure your liability policy is in good order.

#37887 - 05/11/04 11:04 AM Re: Knob and Tube Wiring  
ElectricAL  Offline
Joined: Oct 2001
Posts: 597
Minneapolis, MN USA
The other side of the coin. . .

Extensions from an existing K&T branch circuit have a history of being normal wiring practice. Depending on local ordinance, they may still be legal to create. The NEC still describes how to do it without a j-box.

300.16 includes "fitting" as well as "box". If the open air splice you are looking at has a "monkey face" transition fitting on the end of the NM cable sheath, then the splices to the existing K&T are permitted without a box exclosing them.

Al Hildenbrand

#37888 - 05/11/04 08:02 PM Re: Knob and Tube Wiring  
HotLine1  Offline

Joined: Apr 2002
Posts: 6,853
Brick, NJ USA
Now there's a fitting name I have not heard of in many years..(Monkeyface)

Back in the 'prentice days we ran accross a lot of K&T, but now it's pretty 'rare' around here. I think the old sleeving is hard to come by, but the monkeyface??? Maybe antique roadshow!



#37889 - 05/11/04 09:13 PM Re: Knob and Tube Wiring  
harold endean  Offline
Joined: Feb 2002
Posts: 2,233
Boonton, NJ
I should use a plastic box for the K&T otherwise you might have to cut a slot in the metal box if the 2 wires go through different openings.

#37890 - 05/11/04 11:07 PM Re: Knob and Tube Wiring  
ElectricAL  Offline
Joined: Oct 2001
Posts: 597
Minneapolis, MN USA

I haven't seen a real monkeyface for sale in a very long time, either. This image shows one that terminates the armor sheath on BX cable. [Linked Image]
The basic function is that of a weatherhead, that is, end the raceway or cable and let the individual conductors run on in open air.

If one were to transition now from NM to K&T, using contemporary material, I'd suggest using a threaded ½" weatherhead with a ½" threaded romex clamp.


Al Hildenbrand

#37891 - 05/12/04 07:13 AM Re: Knob and Tube Wiring  
winnie  Offline
Joined: Sep 2003
Posts: 649
boston, ma
I do not know if the below stuff is _listed_ for the application, though the catalog claims 'UL recognized', which I belive applies to components going into apparatus as opposed to finished products. Is this stuff be suitable as the 'sleeving' described? If so, it is pretty easy to get. We use it in our lab for low voltage motor terminations.

McMaster-Carr electrical sleeving catalog page


#37892 - 05/12/04 10:03 AM Re: Knob and Tube Wiring  
ElectricAL  Offline
Joined: Oct 2001
Posts: 597
Minneapolis, MN USA
Over at EC&M, there is a question and answer about this very topic. It is from 2001 and is under the 1999 NEC, but the answer is still accurate, although the code citation numbers shifted some under the 2002 NEC. The NM to K&T splice is the third question, the question at the bottom of the page.

Al Hildenbrand

#37893 - 05/12/04 04:53 PM Re: Knob and Tube Wiring  
Joe Tedesco  Offline
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
winnie, looks like they may:

UL Lists this product:

These listings include woven flexible nonmetallic tubing (fiber loom) in
trade sizes 7/32 to 2-1/2 in. incl. for installation as mechanical protection
in accordance with Articles 320 and 324 of the National Electrical Code.
The basic standard used to investigate products in this category isUL3,
‘‘Flexible Nonmetallic Tubing’’.
The Listing Mark of Underwriters Laboratories Inc. on the product is the
only method provided by UL to identify products manufactured under its
Listing and Follow-Up Service. The Listing Mark for these products
includes the UL symbol (as illustrated in the Introduction of this Directory)
together with the word "LISTED," a control number, and the product
name "Nonmetallic Flexible Tubing".[/quote]

Joe Tedesco, NEC Consultant

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