knob and tube

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tomP

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Background: I am a journeyman electrician dealing with industrial electrical maint. for the last 30 years.
I have a limited knowledge of residentual wiring having served my apprenticship with an EC where we did a lot of residentual work.

My problem is I purchased a house with knob and tube wiring and some romex circuits. Some of the newer circuits are fine,
but some in the second floor are tapped off the knob and tube using solder and tape splices. These circuits have the ground wires cut off, since there is nothing to connect it to. Several of these taps feed GFCI receptacles in the second floor bathroom.

I wish to make this installation "good" before I have the attic insulated.
What are my options? What would you do if it were a house you planned on living in?

I have read thru article 394 and a lot of topics on this forum researching this and will continue to read until I decide what to do .
Any and all code references and suggestions would be helpful.
I have not talked to the AHJ yet as this house is in another state 300 miles from where I presently live.

Thanks
Tom
 
tomP said:
...What would you do if it were a house you planned on living in? ...
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I would be planning on rewiring all those areas that are presently fed from the old knob and tube system. Been there, done that.
 
Short of pulling new cables in from CBP to the rooms stated you can repair if needed and insulate.

If addition, you could add 2008/combination AFCI breakers on the circuits in question and change devices.

I wouldnt worry myself about if the taps are good. Some of that "old" wiring in houses was installed by some damned good electricians.

Ive been an electrician for over 30 years too and in my house of 20 I still have K&T in excellent condition. Its not broke so I dont fix it.

Kind of like respecting methods and practices of are trade, from the past.

Few of us could, not me, wire a house with K&T with the craftmanship those electricians provided. Me, personaly, the advent of short circuits is greatly reduced except in panels and boxes. When done as they did it. It was then and still is a very "solid" wiring method.

2Cnts
 
dumb question. (again)

dumb question. (again)

OK, I can't stand it any longer....... I have to ask a dumb question. (again) I think I know what knob and tube is, but why is it called that? I'm industrial so I'm very dumb on house wiring!
 
hockeyoligist2 said:
OK, I can't stand it any longer....... I have to ask a dumb question. (again) I think I know what knob and tube is, but why is it called that? I'm industrial so I'm very dumb on house wiring!
Click to expand...

 
ARTICLE 394 Concealed Knob-and-Tube Wiring
I. General
394.1 Scope
This article covers the use, installation, and construction specifications of concealed knob-and-tube wiring.
394.2 Definition
Concealed Knob-and-Tube Wiring. A wiring method using knobs, tubes, and flexible nonmetallic tubing for the protection and support of single insulated conductors.
Open wiring on insulators (Article 398) is required to be exposed, whereas knob-and-tube wiring is allowed to be concealed. Conductors used for knob-and-tube work may be of any general-use type specified by Article 310.
 
hockeyoligist2 said:
OK, I can't stand it any longer....... I have to ask a dumb question. (again) I think I know what knob and tube is, but why is it called that? I'm industrial so I'm very dumb on house wiring!
Click to expand...

because of the porcelain knobs that clamp and secure the wires, and the porcelain tubes used wherever it passes thru framing.

I think the old soldered splices hold up better than a lot of modern work, but I'm a little queasy about the insulation. Sure, it's thicker, but often seems pretty crunchy.
 
Would the romex tapped into the knob and tube pass an inspection?
According to 394 you can continue a circuit in knob and tube, but how about romex?
Basically these are the taps I'm worried about, not the original wiring.
 
394.12 Uses Not Permitted
Concealed knob-and-tube wiring shall not be used in the following:
(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 envelops the conductors

2005 Handbook:
Concealed knob-and-tube wiring is designed for use in hollow spaces of walls, ceilings, and attics and utilizes the free air in such spaces for heat dissipation. Weatherization of hollow spaces by blown-in, foamed-in, or rolled insulation prevents the dissipation of heat into the free air space, resulting in higher conductor temperature, which could cause insulation breakdown and possible ignition of the insulation.

394.56 Splices and Taps
Splices shall be soldered unless approved splicing devices are used. In-line or strain splices shall not be used.

Its a toss up right now becaused you havent insulated. And the taps are good. Most inspectors I know would turn white in the face and scratch their heads. If their experienced they would know that they see the same thing all the time BUT, IMO, 9/10 would fail it.

In my home in my walk up attic, I have K&T thru memebers covered with loose insulation and then 3/4T&G boards. Its all original. It must have passed when built. 1954.

But as of today, once you insulate then a code violation would occur.
 
About half of the wiring in my 1922 house is original K&T. I don't have any plans to yank it out anytime soon. Someday I'll get ambitious and do it, but I don't see it as a safety problem.
 
Gmack said:
394.12 Uses Not Permitted
Concealed knob-and-tube wiring shall not be used in the following:
(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 envelops the conductors

2005 Handbook:
Concealed knob-and-tube wiring is designed for use in hollow spaces of walls, ceilings, and attics and utilizes the free air in such spaces for heat dissipation. Weatherization of hollow spaces by blown-in, foamed-in, or rolled insulation prevents the dissipation of heat into the free air space, resulting in higher conductor temperature, which could cause insulation breakdown and possible ignition of the insulation.

394.56 Splices and Taps
Splices shall be soldered unless approved splicing devices are used. In-line or strain splices shall not be used.

Its a toss up right now becaused you havent insulated. And the taps are good. Most inspectors I know would turn white in the face and scratch their heads. If their experienced they would know that they see the same thing all the time BUT, IMO, 9/10 would fail it.

In my home in my walk up attic, I have K&T thru memebers covered with loose insulation and then 3/4T&G boards. Its all original. It must have passed when built. 1954.

But as of today, once you insulate then a code violation would occur.
Click to expand...

Any of it that is insulated is not only illegal but a fire hazard.
Please rewire anything that is about to be insulated,we cant afford to loose members from needless fires.
 
1793 said:
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Cool. I've seen houses that I know were wired with K&T, but I've never seen the walls off of one.

Out of curiousity, what's the outside diameter on the tubes? I assume the studs are 2" by 4" (not to be confused with 2x4's), and by eyeball those are pretty fat wires. If I whack the tubes with a hammer, will they shatter and then I could run 12/2 or 12/3 Romex through the nice little holes?
 
tallgirl said:
Cool. I've seen houses that I know were wired with K&T, but I've never seen the walls off of one.

Out of curiousity, what's the outside diameter on the tubes? I assume the studs are 2" by 4" (not to be confused with 2x4's), and by eyeball those are pretty fat wires. If I whack the tubes with a hammer, will they shatter and then I could run 12/2 or 12/3 Romex through the nice little holes?
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From my experience, you should be able to pull a 12/2 or 12/3 through the hole. Were you planning on leaving the K&T wire or pull it out?
 
1793 said:
From my experience, you should be able to pull a 12/2 or 12/3 through the hole. Were you planning on leaving the K&T wire or pull it out?
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Pull it out. In most instances the walls have to come off. We gutted one house where the crew was instructed to leave the lathing up, but I think that was a huge mistake since that house had had 5' of water inside of it for several weeks. So, I was wondering if I could smash the tubes and pull Romex through it. Sounds like that's a possibility, and since there's a pair of tubes for each circuit, as I understand it, doubling the number of circuits should be easy.
 
tallgirl said:
Pull it out. In most instances the walls have to come off. We gutted one house where the crew was instructed to leave the lathing up, but I think that was a huge mistake since that house had had 5' of water inside of it for several weeks. So, I was wondering if I could smash the tubes and pull Romex through it. Sounds like that's a possibility, and since there's a pair of tubes for each circuit, as I understand it, doubling the number of circuits should be easy.
Click to expand...

If you are pulling the wire then you should be able to pull the Tubes out and SAVE them. You may have a use for some down the road.
 
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