Knob and Tube

[al hildenbrand]

Re: Knob and Tube

Originally posted by Matt Harp:
I have seen grounded knob and tube. I do believe it was a "homeowner" refit. Whoever did it fished . . .

What you saw sounds like what happens when 250.130(C) is applied to ungrounded K&T behind closed walls.

What's fascinating about the house dlhoule worked on in 1968 is it was new construction that was roughed in with K&T for the first time in 1968.

In the '65 & '68 NEC? Concealed Knob-And-Tube Work was in Article 324. Article 324 had no "Special Permission" requirement then, no "for extensions only" limitation. Article 324 was still a viable wiring method, then in 1968, but the Grounding Electrode System (GES) and equipment grounding requirements would have presented application challenges.

Over the years, I've occasionally wondered what roughing in K&T with a ground wire might have turned out like.

The new construction K&T that dlhoule worked on had no GES at all. . .bet that was an interesting discussion with the AHJ.

 

[LarryFine]

Re: Knob and Tube

Originally posted by dlhoule:
How many of you have seen residential wiring in rigid conduit. Now that is a real pain in the ???.

I have, and in the same house as K&T.

There was black-painted rigid from the fuse box to the basement-ceiling boxes, and stubbed up into steel receptacle boxes in the downstairs baseboards, and K&T out of those to everything else.

An opened wall during a remodel showed that both the conduit and the K&T were original to the house. It wasn't old enough to have had gas lighting, but I've done plenty of houses that had gas piping, and had K&T added.

When the ceilings and walls were stripped, you could tell which two floor boards in the upstairs hallway had been lifted for the front-to-back runs, and the joists bored at an angle from above.

The electricians were obviously adept at fishimg wires. The switching loops were interesting, too, especially the 3-way circuits for the hallway and stairs lighting.

 

[LarryFine]

Re: Knob and Tube

Originally posted by dlhoule:
I might add that knob & tube is much more labor intensive than romex.

That's like saying that driving ground rods with a sledge hammer is much more labor intensive than is using a rotary hammer.

Well, yeah!

 

[LarryFine]

Re: Knob and Tube

Originally posted by Matt Harp:
Whoever did it fished a #10 thhn ground to each of the electrical openings and back to the panel. You know, open joints in the attic, etc. I suppose this arrangement would at least provide minimal protection so long as nothing got cut or broken, but seems to me it would have been easier and safer to just rewire in romex.

Without exception, every time I have been asked about grounding the receptacles in an old house (and ascertained there were no ground wires), I recommended running a new circuit just for the places they'd be needed, such as computers, AV equipment, appliances, etc.

I have never run just a grounding conductor for this purpose, and I've been wiring for (holy moley!) 35 years. (I did my first service change when I was 16.)

[ February 14, 2006, 06:39 PM: Message edited by: LarryFine ]

 

[al hildenbrand]

Re: Knob and Tube

In my work area, there is a long history of the Housing Inspector writing up work orders on licensed rental units. The work orders detail small improvements to existing construction to meet the new "minimum maintenance code", a local code.

The grounding of bath luminaires with exposed metal surfaces is one of the very old safety requirements.

There are a LOT of bath luminaires grounded to the cold water pipe around here. Just pop the medicine cabinet out of its recess, run a 14/2 to a new GFI for a new convenience outlet, and continue the EGC from the GFI to a cold water pipe clamp. -Note: Most bath luminaires were pullchains, originally, in the K&T era around here.

If I were to have run new romex to ground the luminaire / GFI, I would have priced myself right out of the competitive bidding and never gotten the jobs.

 

[dlhoule]

Re: Knob and Tube

I have never run just a grounding conductor for this purpose, and I've been wiring for (holy moley!) 35 years. (I did my first service change when I was 16.)

 

[dlhoule]

Re: Knob and Tube

Originally posted by hardworkingstiff:

Originally posted by dlhoule:
Gentleman having it built was familiar with code and swore by knob & tube. He said he had never heard of a fire caused by knob & tube wiring, other than when being extremely overloaded.

I wonder how many romex fires were started with wiring that was NOT overloaded?

That is such a lame statement by that man. Insulation was not common back then, so the knob and tube system ventilated well.

I would wonder though, if devices were actually built more durably back then.

I wonder how many romex fires were started with wiring that was NOT overloaded?

Well, for one thing you are much less apt to have screw or nail short knob and tube.

 

[dlhoule]

Re: Knob and Tube

It wasn't old enough to have had gas lighting, but I've done plenty of houses that had gas piping, and had K&T added.

That reminds me of time I had HO wanting a light installed in center of living room. There had been a gas light at that location. As I started taking gas pipe apart to install ceiling box, I smelled gas. At first I thought it was probably just a little residual gas trapped in pipe. However, after waiting a few minutes and loosening pipe more I could feel the air movement from pressure. The city initially said there was no way it could still be under pressure. It took them a total of six days to find how it was being fed and correct problem. It seems that original owner had made an illegal tap that they were unaware of.

 

[al hildenbrand]

Re: Knob and Tube

Originally posted by dlhoule:
that original owner had made an illegal tap . . .

LOL

Heh! Even gas piping?!!! Until you wrote it, I'd never considered it. . .sure is obvious now.