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More Knob and Tube #151549
03/06/03 08:44 PM
03/06/03 08:44 PM
Admin  Online Content
Joined: Oct 2000
Posts: 3,481
[Linked Image]
Anatomy of a K&T conductor. Cloth over rubber over (tinned??) copper

[Linked Image]

Closeup of a K&T splice

[Linked Image]

Knob-and_tube wiring--notice the gas pipe from a gas light (ceiling shot)

[Linked Image]

This was behind a bathroom wall.


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Re: More Knob and Tube #151550
03/07/03 08:02 AM
03/07/03 08:02 AM
Texas_Ranger  Offline
Joined: Dec 2001
Posts: 2,409
Vienna, Austria
The wires look exactly like Austrian phone wire like it was used in the 1930ies and earlier, only the conductors were twisted around each other (3 wires). They also had the colored stripe.
I've often seen gas pipes in ceilings, most of them still connected to the supply. In many cases there would be a stopple with a hook in it, to hang the light fixture. In most cases solid enough to hang an elephant.
Expert splice, and without doubt perfectly accesible! [Linked Image]
Power wires usually looked the same but the cloth was impregnated with a bituminous compund. Makes for absolutely black fingers when working with that stuff!

Re: More Knob and Tube #151551
03/07/03 08:06 PM
03/07/03 08:06 PM
electure  Offline

Joined: Dec 2000
Posts: 4,264
Fullerton, CA USA
I've come across some old K&T that's been in pristine condition. Sometimes it makes me kinda sad to tear out the old stuff and put in new plastic parts. It used to be a heck of a lot of work to drill with a brace and bit. You've got to appreciate their attitudes when nowadays guys don't even carry screwdrivers, but just a couple of different bits for their cordless drill.
(Check out the "labor intensive" lath in the wall with the flying splice)

Re: More Knob and Tube #151552
03/10/03 12:12 AM
03/10/03 12:12 AM
SvenNYC  Offline
Joined: Aug 2002
Posts: 1,691
New York City
I know the "knobs" are still sold...but usually it's now used for attaching antenna wire to a building....or things like electric "bird repellers."

A mail order supply house that caters to the old-radio repair hobby carries them (

What about the ceramic tubes, are they still manufactured?

I wonder if an electric supply house counterman would look at me weird if I went in and asked for knobs and tubes....of course I guess nowadays you'd have to use THHN/THWN wire instead of that cloth & rubber coated stuff, so it would DEFINITELY be breaking a whole lotta codes in the book! [Linked Image]

Re: More Knob and Tube #151553
03/10/03 01:18 PM
03/10/03 01:18 PM
kale  Offline
Joined: Nov 2002
Posts: 174
Porcelain Products shows standard porcelain tubes and 5 different kinds of knobs in their catalog. Unfortunately, their website does not show their products.

Re: More Knob and Tube #151554
03/10/03 09:31 PM
03/10/03 09:31 PM
stamcon  Offline
Joined: Mar 2001
Posts: 330
So San Francisco CA
K&T is still allowed for extensions on existing installations or elsewhere with special permission. Article 324

Re: More Knob and Tube #151555
03/16/03 09:46 AM
03/16/03 09:46 AM
ldwilson  Offline
Junior Member
Joined: Mar 2003
Posts: 4
As professional electricians what are your feelings about leaving K&T in place in older homes.
As a licensed home inspector I have seen some really scary K&T in place and always recommend that one of you evaluate the wiring for replacement.
As I understand, most K&T applications are okay as long as the sheathing isn't breached. But I have never seen a home with K&T that some amature hadn't made at least some modifications to add ceiling fans, bathroom vent fans, etc.
Thanks for the input.
Larry W.
South Carolina

Larry W.
Re: More Knob and Tube #151556
03/16/03 08:56 PM
03/16/03 08:56 PM
ThinkGood  Offline
Joined: Aug 2002
Posts: 1,081
Milwaukee, WI

I'm not an electrician, but I can tell you that the electrician who was hired to rewire the house in the photos said he is going to disconnect all of the K&T, as it is at least 70 years old.
- - - -

Something else I just noticed, third photo down...Where there is a tube that sits on top of another tube (perpendicular to it), small coils of wire were placed on either end of the tube to keep it from sliding. I saw this in similar situations throughout the house. Seems that nothing went to waste back then...

Regarding the last photo shown, no box was used to enclose the splice, and the Romex is not supported properly.


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