knob and tube question

[blazenut]

I inspected a home today that was around 80 years old. I assumed that i would run into k and t somewhere in the home and sure enough i did. I did however see something that i never saw before, and i cant figure out why this would be done (see below pictures). A live feed of knob and tube came into this section of a side attic and simply zig zagged back and forth, un-sheathed (?), and just terminated at the end of the zig zag. Why would this be done? Like i said, my continuity tester read that it was live. Thanks.

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[Neal Lewis]

Which is the hot and which is the neutral? I would think it is more like some type of antenna. Knobs & tubes used for something other than 120 volts.

[blazenut]

It was only a single wire than ran back and forth, when it passed through the first ceramic housing it went from being fabric sheated to bare copper. I thought of it being an antenna but would that show a possive continuity reading for an antenna? The wire came up from never never land (from an unknown area).

[Jim Katen]

It was only a single wire than ran back and forth, when it passed through the first ceramic housing it went from being fabric sheated to bare copper. I thought of it being an antenna but would that show a possive continuity reading for an antenna? The wire came up from never never land (from an unknown area).

It's a radio antenna. Extremely common (in my area you're nearly guaranteed to find it) in houses from the 30s, 40s, & early 50s.

As for your "continuity" tester, what exactly are you talking about? A continuity tester has a small battery in it and is used to show continuity of a wire, not the presence of voltage, as you seem to be implying.

Are you sure you weren't using a non-contact voltage detector? If so, those things give false positive readings all the time and false negative readings every so often. Never, and I mean never, trust one in a critical application. In a situation like this one, in particular, a volt stick is almost always going to show voltage in the wire even if you can see both ends of the wires dangling in the air.

- Jim Katen, Oregon

[blazenut]

Thanks Jim, and yes I was using a non-contact voltage detector. And yes, i have noticed that they give false readings often, usually it is a weaker signal though.

[John Dirks Jr]

I found this antenna stuff in a 1941 house.

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[blazenut]

Thanks guys.

[hausdok]

Hi,

I've had a volt stick detect voltage in old radio antenna when the antenna passed near some live wiring and picked up the field of the electrical wire. Once, I moved the NM away from the antenna (It wasn't secured anyway) and the volt stick stopped indicating voltage on the antenna.

ONE TEAM - ONE FIGHT!!!

Mike

[barlyhop]

The above replys would seem to be accurate. The only other scenario that I could fathom would be perhaps the k&t were relocated due to adding insulation at some point as k&t cannot be buried in insulation.

[hausdok]

The above replys would seem to be accurate. The only other scenario that I could fathom would be perhaps the k&t were relocated due to adding insulation at some point as k&t cannot be buried in insulation.

I think you mean it "may" not be buried in insulation; because one can certainly bury it if one has a mind to.

You'd be wrong here. It's allowed to be buried here and it's done all the time. Doesn't make it right. Doesn't make it any safer. But it's an indisputable fact.

WAC 296-46B-394 Wiring methods and materials — Concealed knob-and-tube wiring.

001 Knob-and-tube wiring.

Article 394 NEC does not prohibit the installation of loose or rolled thermal insulating material in spaces containing existing knob-and-tube wiring provided that all the following conditions are met:

(1) The wiring must be surveyed by an appropriately licensed electrical contractor who must certify in writing to the department that the wiring is in good condition with no evidence of improper overcurrent protection, conductor insulation failure or deterioration, and with no improper connections or splices. The electrical inspector must inspect all repairs, alterations, or extensions to the electrical system.

(2) The insulation must meet Class I specifications as identified in the Uniform Building Code, with a flame spread factor of twenty-five or less as tested using ASTM E84-81a. Foam insulation may not be used with knob-and-tube wiring.

(3) All knob-and-tube circuits must have overcurrent protection in compliance with NEC Table 310.16, 60 degree centigrade, Column C. Overcurrent protection must be either circuit breakers or Type S fuses.

[statutory Authority: RCW 19.28.006, 19.28.010, 19.28.031, 19.28.041, 19.28.061, 19.28.101, 19.28.131, 19.28.161, 19.28.171, 19.28.191, 19.28.201, 19.28.211, 19.28.241, 19.28.251, 19.28.271, 19.28.311, 19.28.321, 19.28.400, 19.28.420, 19.28.490, 19.28.551, 2002 c 249, chapters 34.05 and 19.28 RCW. 03-09-111, § 296-46B-394, filed 4/22/03, effective 5/23/03.]

ONE TEAM - ONE FIGHT!!!

Mike

[barlyhop]

Thanks Mike, I stand corrected. It's been so long since my training and I always recommend further evaluation by qualified electrician when I find buried K&T.

Randy

[John Kogel]

Hi,

I've had a volt stick detect voltage in old radio antenna when the antenna passed near some live wiring and picked up the field of the electrical wire. Once, I moved the NM away from the antenna (It wasn't secured anyway) and the volt stick stopped indicating voltage on the antenna.

ONE TEAM - ONE FIGHT!!!

Mike

Yes. Because there's a possibility that the bare antenna wire has come in contact with live K+T in that attic, would you recommend someone get up there with a real voltmeter to make sure?