Correct way to splice knob and tube wiring.

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  #1  
Old 01-05-07, 04:17 PM
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Correct way to splice knob and tube wiring.

I purchased my home 6moths ago. I would like to install some exterior motion detector flood lights and tap into the power supply in the attic. I was horrified when I saw how the former owner tapped into the power supply to power newer recessed lights in the kitchen and other things. I am obviously going to have to correct those areas. What is the proper method to splice into knob and tube wiring?

It seems like the splice should be made inside of a junction box. The previous owner spliced into a line and used electrical tape to secure the connection. Some connections dont even have pigtails.
 
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Old 01-05-07, 04:59 PM
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DON'T. Start fresh. Just my humble oppinion.
 
  #3  
Old 01-05-07, 05:11 PM
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While existing K&T wiring is OK under many local codes, extending it is not allowed. Which means, no splices, anywhere. Check your local code authority.
 
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Old 01-05-07, 06:13 PM
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I'm with stupid... (thats lee for everyone else)...start over with a new NM cable if only from the switch at least
 
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Old 01-05-07, 06:41 PM
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Thanks Pal.... Don't you know I'm sensitive... And the therapy is not going as well as planned.
 
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Old 01-05-07, 06:56 PM
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So when the former owner installed recessed light, what should they have done? Installed a new circuit?

How should I handle the areas where splices have already been made? I will try to get up there and take some pictures so you people can see this.
 
  #7  
Old 01-05-07, 07:46 PM
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You cannot extend the knob and tube. You must start fresh.

Correct the previous mistakes by running one or more new circuits to the attic and connect the knob and tube splices that you remove to the new circuits you run.

Depending on what is on these extended circuits, you may be able to combine them with your one new circuit you will be running.
 
  #8  
Old 01-05-07, 08:31 PM
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I understand what I need to do as far as running the new circuits.

How do I handle the exposed knob and tube wire once I remove the splice? How do I reinsulate the wire? I doubt electrical tape can handle heat generated by a short circuit if that were to happen. The knob and tube wire in the attic does not have the samE black fire retardant sheeth that the wires in the wall have.

One other thing. Some of the "knobs" appear to be in poor condition. What can I use to secure the tubes and prevent them from sagging.
 
  #9  
Old 01-05-07, 08:38 PM
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Ultimately you must replace the knob and tube. The sooner, the better, at least with the damaged sections.
 
  #10  
Old 01-06-07, 06:07 AM
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So when the former owner installed recessed light, what should they have done? Installed a new circuit?
===============

As knob and tube wire has gotten older the rules have changed. At one time it was legal to tap into K & T if done properly. I am old so I am talking a very long time ago. It is no longer legal to extend a circuit that has any part made of knob and tube, because the wiring is so old that it is no longer safe, and should be replaced.
 
  #11  
Old 01-06-07, 08:09 AM
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Unless local rules prohibited it, extending knob and tube circuits was allowed in the 1999 NEC. There were areas of the country that hadn't adopted the 2002 edition of the NEC yet last time I checked which would make extending these circuits still legal in these areas.

I bring this up only because of how people react to K&T issues sometimes. It is possible to have a not-to-old K&T extention installation that is completely legal. A typical tap splice is made by wrapping the wire to be added around the existing one and the joint is soldered then taped. Also allowed was using a wire nut or similar. Tap splices weren't made in boxes. K&T wiring that hasn't been hacked up is very often still adequate for lighting circuits and gets replaced in many cases only because you can't insulate around it.

That said, you are much better off installing a modern grounded circuit any time you have the need to change anything where K&T is involved and have no choice most places. Many of the additions to K&T weren't done to code and more problems probably happen because of this than because of K&T itself. While it may have been legal, extending K&T hasn't been a good idea for a very long time. Among other reasons is disturbing the insulation on the wire can be a very bad thing as it is often brittle. If your wire still has insulation that is flexible to some extent, once you remove the wires that concern you, cover the area with rubber tape and then over tape with regular vinyl electrical tape. If the insulation starts breaking off in the process you need to replace the circut.

None of this should be construed as endorcing installing K&T, it is only intended for information. I was always amazed that the method stayed in the code as long as it did.
 
  #12  
Old 01-06-07, 09:22 AM
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When replacing exposed K and T wiring in the attic, what is done? Is all the wire replaced behind the walls as well or is the exposed attic wire only replaced? In my home the attic wiring is my main concern. It does not seem very difficult, just labor intensive. I can't imagine fishing wire to each switch and outlet in a home.
 
  #13  
Old 01-06-07, 10:28 AM
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When you begin replacing any part of a K&T circuit you need to do it all. You won't be allowed to tap the in-wall K&T wire into the new attic wiring. Which means you will be fishing to all the associated fixtures, receptacles, and switches. Yes, it's a lot of work which is why professional rewiring quotes to repalce K&T and aluminum are never cheap.

A bit of thought about the placement of J-boxes will let you run new a new circuit(s) to the attic and TEMPORARILY feed the K&T till you can get it replaced and allowing you to do the other work you have in mind.

When you feed the K&T with a temporary connection, it is usually better to cut the K&T near a knob, or insulator, and wire nut the NM-B to it there rather than trying to get the K&T into a box as insulation damage is usually the result. The rules used by K&T dictated that the wire was to be 3" away from the structure that supports it (wood framing),, unless run through a tube that went through the framing, and as long as you continue this as you work your way toward replacing the stuff you should be OK.

Temporary in this case means allowing you to use the house as usual while the rewiring is going on and not a 6 month hiatus while you get up the gumption to finish. A weekend or two needs be be the limit
 
  #14  
Old 09-25-13, 12:57 PM
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Knob & Tube Wiring

Just an FYI to all ... someone needs to re-read the NEC - section #394; its still legal and does not have to be taken out! Below is taken from the 2011 code book, pages 493 - 495.

Section 394.10 describes uses
(1) For extensions of existing installations

Section 394.12 Uses Not Permitted
(1) Commercial Garages
(2) Theaters and similar locations
(3) Motion Picture studios
(4) Hazardous (classified) locations
(5) Hollow spaces of walls, ceilings and attics where such spaces are insulated by loose, rolled or foamed-in-place insulating material that envelopes the conductors

304.23 In Accessible Attics (deal with headroom)
(A) Accessible by stair or permanent ladder
(B) Not accessible by stair or permanent ladder
 
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