Issues with rewiring Knob & Tube

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  #1  
Old 06-18-01, 09:16 PM
Able Sashweight
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This 80 year old house has largely knob & tube wiring, in some places extended with new and old NM spliced and taped. Walls are generally lath & plaster, except for some tile and Formica in the kitchen. I plan to rewire a good bit of this.

Three questions:

1. What is best practice for abandoning wire when it cannot be removed without opening the wall? Tape or nut it off? label it? Cut it off as far inside as possible, or leave a coil of the remnant where practical? Any tips for removing knob & tube that is inside the walls?

2. Sometimes I will want to replace part of a K&T branch circuit with NM. How should the splices be made? If I was extending K&T, I'd use ordinary K&T splices yet I understand that's only ok for K&T to K&T, not to NM or THNN.

Situations are:
A. Up run becomes NM leaving tails of K&T. This will be the main case
B. Down run becomes NM leaving a head of K&T. This occurs when converting the run to a switch or receptcal to NM, leaving the rest of the branch circuit alone. This case is problematic since it does not leave the fixture grounded, which is a goal.

3. Some of the K&T runs inside the wall of the water heater closet, which wall is open to that closet. Can I leave NM exposed in here, or would it need to be in conduit? This closet is pretty cramped, and although a skinny person can wriggle in (but not move once in), no one else could.

Thanks,
Able
 
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  #2  
Old 06-19-01, 07:35 AM
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I advise you to think "long-term" and install all new wiring and remove all existing exposed wiring- trying to utilize any existing wiring is false economy.Consider outlets for window AC units if central AC is not feasible.You state "wall of closet which wall is open to closet." ????. All verticle cable runs should be fished in partitions and cables exposed only in the attic or cellar.I suggest you work from the "top down",i.e.,rewire the 2nd floor first.Also consider telephone?T.V./ computor cables.
 
  #3  
Old 06-19-01, 10:23 AM
Able Sashweight
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>I advise you to think "long-term" and install all new wiring and remove all existing exposed wiring- trying to utilize any existing wiring is false economy.

Agreed.

>Consider outlets for window AC units if central AC is not feasible.

Reasonable point.

>You state "wall of closet which wall is open to closet." ????. All verticle cable runs should be fished in partitions and cables exposed only in the attic or cellar.

The water heater closet is the one with uncovered inside walls. The opposite side of one of its walls is part of the hallway wall, and the opposite side of another wall is the livingroom. From the inside of the closet, I see the back side of lath and plaster. And there is K&T wiring visible, and the back side of hallway wall switch, and the backside of a livingroom receptacle.

>I suggest you work from the "top down",i.e.,rewire the 2nd floor first.

Why?

>Also consider telephone?T.V./ computor cables.

Yep.

Able
 
  #4  
Old 06-19-01, 10:29 AM
Able Sashweight
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switchman:

There will be at least one pair of K&T wired fixtures which I doubt I can fixh or pull new wire to. In that case splicing between NM and K&T will be necessary, and I'll need to know the rules.

Able
 
  #5  
Old 06-19-01, 11:27 AM
Wgoodrich
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knob and tube spliced to new Romex suggested as follows;

Nail a nonmetallic box at the end of the knob and tube to be spliced. Run each knob and tube wire individually into its on box entry. Install the Romex into another entry of that box. Wirenut black of Romex to black of knob and tube. Wirenut white of Romex to white of knob and tube. If you have no color id on the old knob and tube touch a tester to the knob tube wires individually with the other end touching a water pipe. The wire that moves the needle should be the black and the wire that does not or barely moves the needle should be your white wire. The bare wire in the new Romex should be cut off at the sheathing if you use a nonmetallic box. If you use a metallic box connect that bare wire of the new romex to that metal box if that new romex is a power source. If that new romex is an extension then cut off that bare wire at the sheahing not to be used. Don't forget to use a blank plate to close that junction box and ensure that junction is accessible for future conditions.

Hope this helps

Wg
 
  #6  
Old 06-19-01, 12:13 PM
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Hi Able- I mention the 2nd. floor because you will have to examine the structure and decide on the best way to run branch-circuits to the 2nd floor rooms and attic.Perhaps there are interior partitions "in line" or a 2nd. floor closet where you can drill down into the Ist floor partitions. You may want "up and down" 3-ways for the 2nd. floor stair, future or new HVAC contol wires.You mention a problem acess to 2 fixtures-are thay switch-controlled and where are they located?-the K&T must be replaced.Would a #4 feeder to a 2nd floor panel be feasible?Is the attic finished? etc. Progress!!
 
  #7  
Old 06-19-01, 11:04 PM
Able Sashweight
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WG: So keep the splices in an accessible covered box. I'm interpreting that as "code requires it as well as does good practice." Keeping them accessible is a doable hassle, even as its mandatory.

switchman. Single story structure with an unfinished attic. The problematic fixtures are switch controlled. They are a pair of decorative "flame" lamps on the face of the fireplace. The front of the fireplace is built out from the wall, from floor to ceiling, with the wires inside the built out part. I can see where the wires emerge from the top (from the attic perspective). Maybe its fishable, and if not, I can use a box.

Thanks,
Able
 
  #8  
Old 06-20-01, 09:48 AM
Wgoodrich
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All boxes, junctions, etc. are required to be accessible by the Code. This word accessible means that you can get to that junction, box, etc. without removing or changing the integrity of the structure. accesible attics, crawl, surfaced recessed box in a wall with a face plate, in a closet all would be accessible. You may be able to pull your wires to the attic, or cut the wire in the attic if it is running in the attic. Most knob and tube wiring surface either in the attic or crawl space at some normal location.

The light fixture built into your fireplace will most likely be required to be junctioned and using a part of that older wiring going to those fireplace fixtures. Often the wires were laid right in the masonry itself making replacing them meaning tearing down the masonry wall and relaying the masonry again. This would be impractical in method. I would just use the old knob and tube carrying the limited load of those two light fixtures converted to new Romex as discribed in the previous reply.

Hope this helps

Wg
 
  #9  
Old 06-20-01, 06:21 PM
Able Sashweight
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All of this helps. Thanks,

Able
 
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