What exactly is Knob and Tube?.
I've heard this term used around ECN a bit and I was wondering if someone could tell me what this is?.

trumpy, it was a real old type wring using single conductors where when went through a joist you drilled a hole & inserted a porcelain tube for the wire to go through.the knob was put on the sides of a joist & the wire fit under the top. there are some pics here on the site but just not sure. they will show ya what i'm talking about. :-)ERWIN

Trumpy, go to the electrical nostalgia board and check on "knob and tube wiring". It is a good picture.

Hi Trumpy:
Go to the "Electrical Nostalgia" section here at ECN. There are several threads dealing with Knob and Tube wiring, along with excellent photos.

Mike (mamills)

...OOOOPPSS!! Like Spkjpr said...I guess I was composing about the same time he was...

[This message has been edited by mamills (edited 05-09-2003).]

Hey Thanx Guys!,
Have just checked it out and all I can say is that, this has got to be the strangest wiring method I've seen in a while!.
Are those insulators attached to the sides of them joists?.
I take it that this type of wiring is no longer used?.

Trumpy:
The insulators are nailed into the ceiling joists or wall studs. The insulator comes in two pieces - the wire is sandwiched between the two pieces and the nail holds the entire affair in place. A great many homes still contain Knob and Tube wiring - some in pristine condition, and most in varying degrees of hazardous disrepair (due to physical damage, poor maintenance, and deterioration/overheating from overfusing).

There may be areas of the country where this method of wiring is still permitted, but it is mostly outdated now, in favor of non-metallic sheathed cable, also referred to as "Romex" (a trade name). Knob and tube wiring, as you can see from the pics, is quite a labor-intensive wiring method. Splices are also performed in the open (in violation of modern day NEC codes), along with the fact that there is no provision for grounding of devices such as light fixtures and receptacles.

Mike (mamills)

[This message has been edited by mamills (edited 05-09-2003).]

[This message has been edited by mamills (edited 05-10-2003).]

Mike,
Thanks for the info,
You say that this type of wiring is still permitted in some areas, where?.
When I first saw the pictures, I thought it was a leaning over power pole, with all them insulators.
Also, what type of wire was used?, it looks to me like black rubber, as this was in fashion in the old days, am I right?, are them wires single cores?(1 wire stranded)
You'd have to be careful using the hammer around them Porcelain insulators, one wrong hit and it would be all busted to pieces!.

Trumpy,
I was talking to my inspector yesterday about k&t. He tells me it is still in use down south in flood prone areas. Romex gets wet and doesn't dry out inside. It grows mold and the paper rots degrading the insulation. Knob & Tube can dry out and is fine. The just run 3 wires instead of 2, like the old stuff.

I have no idea were they get the supplies. They aren't available in my area.


Ob

I ran into a house a few years ago that they ran the nuetral down one side of the house and the hot down the other side. They would make a joint in the ceiling light fixtures and drop out the one or two outlets they had in the room along with the switch legs. They had the service panel and metering mounted inside the house on the side of a kitchen cabinet and the whole house had been fed from 2 20 amp circuits. They had tapped one little disconnect for a dryer.I wish I had taken some pictures. The house was a depression era house and the inside walls were made from old dupont powder boxes (There was an old explosives plant from the war era nearby)

Trumpy,

Here in Northern NJ it is very common in homes that are over 100 years old. We will work with it if we have to but for the most part we will rip it out and install new wiring. It is a nightmare to work with. It is old, sometimes frayed, Sometimes mice chew on the insulation, and if it is exposed in the basement some people will even use it for a clothes line! Above all, there is no grounding conductor run with it.

I've filled dumpsters with K&T in my carear.

I suppose at one time it was a premium install, after all much of the world continues to operate on this fairly outdated wiring method

If in fact it was left alone it is usually not the worse for wear, it's when the years of retrofit, tag-on, and similar intervention starts that bad things happen.

20 years ago, a home inspector in his 70's whom had previously been an EC installing K&T told me 'you young bucks are'nt going to top this method'

maybe he had a point? we've been trying to one-up the mighty fuse ever since also.....

1999 NEC
Art. 320 - Open Wiring on Insulators (read knob & tube)

320-3 - Uses Permitted
'Open wiring on insulators shall be permitted on systems of 600v or less only for industrial or agricultural establishments,indoors or outdoors, in wet or dry locations, where subject to corrosive vapors, and for services.

320-5(a)
Conductors shall be of a type specified by Art. 310

ever seen a K&T meter setup?

they're a riot........can't quite find one on the net tonight......
(hint hint....)




somewhat debatable method eh?
from this site

knob....tube!

not enough cobwebs to keep me happy here....

if your good, these go flying with one whack of the hammer...

[This message has been edited by sparky (edited 05-11-2003).]

[This message has been edited by sparky (edited 05-11-2003).]

sparky,
Thanks for the cool pics, mate!!.
This system, seems to me like the most simple of wiring techniques.
Although, you would think that the wires must have been pretty cheap, who these days would run a whole heap of single cores around a building, to effect the same thing as a 3 core or similar?.

Small aside — In sparky’s last picture, porcelain knobs were usually furnished with a ~12-penny nail and with some—a washer of cut leather.

Nowadays, I imagine the high-brow construction junk shops—er, “vintage building restoration and antiquities” firms are probably selling salvaged knobs and tubes at 50 times their original price.

As far as “cutting-in” to existing K&T from modern nonmetallic cable, I have successfully {passed inspection by} using a 3¼-inch metal octagon box, with a clean ~6-inch length of romex jacket as “loom” for single conductors exiting the box. In these cases, just dogged off the bare ground with a standard 10-32 green/hex machine screw, for luckily there was no need to extend an equipment-ground conductor.

If you want knobs and tubes come to Oak Park, IL and you can get about a million of them. Many of the homes are pre and early 1900 and many still loaded with k&t. I have fun all the time trying to get the electrician to tie in the existing k&t properly on partial remodels.

I even saw a non-compliant installation of k&t that looked ok except for the fact that no knobs or tubes were used. Just wire run thru holes in the joists.

Yes even in the early 1900's there were the handy man specials!!

When I worked at the Great Lakes Naval Training Center Fire Department, we remodeled the day room in one of the "out" houses - two bay frame fire houses that had been built as "temporary" structures during WWII, and were still occupied 55 years later...

Chock full O' K&T. Replaced it all w/EMT, but it was still in pretty good shape.

Since someone reopened this thread, Article 324 in the 99 code allows K&T ONLY for extensions of existing, or by special permission.

It is not a grounded system, which is it's worst feature electrically speaking.

Trumpy, think open air, cause that's what this was, it would take lots and not harm anything. Anywhere it touched wood it was insulated with porcelain (if done properly). It was also often done with hard drawn copper, which made it even tougher, and danged hard to cut.

Thanks George,
Knob and Tube just seemed like a really strange way of wiring a house.
But, I suppose they just used what was available back then!.

In Austria (and probably elsewhere in Europe) the earliest way of electrical wiring were twisted cloth wires like old lamp cord on porcelaine insulators, always surface mount, with beautiful porcelaine and brass rotary switches and receptacles mounted on wooden pattresses. In rural areas this wiring method was used well into the 1920ies if not longer. 2 or 3 years ago I saw a house where all that wiring was still in service. There weren't any junction boxes, just open taped splices on the wall. Max. 2 receptacles in each room. In this house I also saw a really weird thing, a piggyback plug. It was an angle plug that plugged into the receptacle and the a second plug went into the back of the plug. I don't think combining more of these would be a good idea...

Trumpy,
Have you ever watched the old Tom & Jerry cartoons? In some of those where we see Jerry's home inside the walls, the cartoonists actually added drawings of some K&T wiring. Keep a look out for it!

Response to Sparky's hint:
Old Service Photo



(from Joe Tedesco)

TexasRanger said:


Christmas tree light-strings made for countries using American-type sockets are wired with such plugs (usually equipped with tiny fuses the size of a pencil point).

There are notices on the boxes that say not to plug more than three of these back to back.

I have frequently seen instances where SIX to TEN of these are hooked together....and there are also pictures of such things here, if someone can find and re-post them.

Great old service photo. Thanks! It brings back some nice memories.

...Wonder what's in the metal box there on the left...?

When I was a young'un living in Denver, My father and I would take groceries to a little old lady who was homebound. Above the doorway from the living room into the kitchen hung one of these old a-base meters, with wires disappearing through four neatly drilled and insulated holes into a flush-mounted box nearby. I got my father to lift me up on his shoulders so that I could open the little door and look at the knife switch and fuses inside.

I guess some people catch the "bug" at a really early age.

Sven: Take a look at the thread entitled "Temporary Holiday Display" in the "Photos Submitted for Discussion" area (on page 3).

Mike (mamills)

[This message has been edited by mamills (edited 06-16-2003).]

A slang/(formal?) term for the ring-pull can is "cutout box."

Another electric meter [upper right-hand] {and wood stove} shot is:


Country Store Interior 2553 Sage Place, Spuyten Duyvil October 11, 1935




[This message has been edited by Bjarney (edited 06-16-2003).]