Knob and Tube Wiring?


Old 02-27-13, 08:54 AM
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Knob and Tube Wiring?

I have recently purchased a home that I believe has some K&T wiring still in use. I am not 100% certain of this however and I have hired an electrician to come out in about a week to check and see exactly how much is present and still in use, but I'm trying to educate myself at the same time. I don't know much abuot what it looks like than the pictures I've seen online.

There is a light fixture in our attic that I believe may be knob and tube wiring but I cannot be sure. Hoping someone can look at the attached image and confirm whether it is or not. Thanks!
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Old 02-27-13, 09:00 AM
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Knob and tube would typically have two pieces of loom entering the box.

K&T had porcelain knobs nailed to the side of the framing to secure the wires and tubes where it went through the framing.
Old 02-27-13, 09:04 AM
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Thanks very much for the response - yes, I have read about and seen the knobs and tubes, particularly in the basement. Most of the wires appear to be cut but I can't be 100% sure. So what type of wire is this in the photo?

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Old 02-27-13, 09:07 AM
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Welcome to the forums.

Hard to tell from the picture but it looks like old cloth covered nm cable.
Knob and tube has two separate conductors that run parallel to each other.

So at that light .... if it was knob and tube there would be two separate wires going into the box.

ON EDIT: I must be getting slow in my old age
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Old 02-27-13, 09:42 AM
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Definitely makes sense to me.

I have concerns about a fixture in the basement also - the only reason I ask abuot this one is due to the fact that there are TWO green wires running into the right side of this fixture as shown, though the wire looks to be the same kind of older cloth covered NM. See photo.

Just verifying that this does NOT look like K&T to any of the experts out there, right?
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Old 02-27-13, 09:50 AM
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Nope not K&T. It is cloth NM, probably ungrounded, but what the heck is up with the light mounting? It looks like the box is screwed to a duct and worse they cut a joist or cord to run the duct.
Old 02-27-13, 09:54 AM
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Thank you for the response! Trust me - the person who owned this home before me did all kinds of crazy stuff...that basement fixture included. But I am glad to see and hear it is not K&T. Thank you to everyone who answered!
Old 02-27-13, 09:58 AM
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I'd like to see another pic of that floor joist/light - from another angle.
The reason the light has 2 wires [cable] is there is another light down stream that gets it's power from the same source [circuit] that light does.
Old 02-27-13, 03:27 PM
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We can't tell from looking at this fixture how many wires the 8-b box has fed into it. What we can tell is that it has three cables fed in, and that all three appear to be early Type NM cables.

If all three are 2-conductor cables, and were manufactured before an equipment grounding conductor (a "ground" wire) was included in Type NM cabling, then there are six wires entering the box.

One interesting thing is that the fixture is switched with a pull chain. Since it only requires the two wires in one cable to power the fixture, it is a reasonable guess that the circuit is being split here to power at least two additional lights or other loads.

That said, it appears from this photo that some of the cables entering the box may be in contact with the round duct above it. If so, that should be corrected.
Old 02-27-13, 04:43 PM
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It looks like the box is screwed to a duct and worse they cut a joist or cord to run the duct.
That is not secured to the duct. That metal bar is used to mount boxes between joists. It bends up and goes over the box that is picture. I have one in the room I am renovating right now.
Old 02-27-13, 06:14 PM
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Yep, that's an old style bar hanger, but they usually extend across two joists and don't run along the joist.

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