I recently went to a home that had existing knob nailed onto floor joists from previous wiring system. The entire system was replaced with non-metallic sheathed wiring and the old wiring was cut just leaving the ceramic knob behind. I tested with a no contact AC tester in which I got a positive reading. This was most likely from the new wiring as it was a stray reading however I decided to write it up for an evaluation. Does this even require a write up since non of the ceramic knobs were connected to anything? I never understand why they don’t remove these to eliminate any question. Thanks in advance
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Because electricians don’t work cheap.
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The ceramic Knobs and Tubes are nothing more than insulators. Period. They are a non-issue. Only the conductors themselves are required to be removed, not the insulators.
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Thank you for the response. This was my original thought.
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Ah, a better than average job then :-).
Usually they just leave the old wiring in place, to maximize future confusion.
Showing photos is better to get good advice.
The ceramic knobs are passive, just a nail and ceramic.
Stray readings are not reportable.
Search the home for fuses, weird junction boxes, and more that could be wrong with the Knob & Tube replacement project. But the ceramic knobs and tubes are doing no harm, and will outlast your modern wire and all your dental work. They’re fine.
A good indicator of hidden remaining knob & tube is grounding. Either 2 prong outlets, or 3 prong outlets with no ground connection. Chances are… those are remaining k&t wires, and where it splices to modern wire is the trouble point.
In the best case, those splices are at what used to be a fuse box, and now is just a junction box.
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The problem for all of us with knob and tube is not what you can see, it is the wiring that you cannot see. It is often routed under insulation in the attic, in wall cavities etc. So, when I write it up, I describe what I could see and disclaim what I could not see (as above). I will then recommend further evaluation.
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So there was no knob and tube wiring copper conductors left after they upgraded to NM cable? Is so then there is nothing to report. Also even when K&T is de-energized and replaced there is no requirement to remove the old conductors.
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IMO K&T components should be reported. This is not based on code or requirements but rather experience. On more than one occasion, I have been in updated homes with energized K&T located in inconspicuous locations (such as under attic ceiling insulation) but in open clear areas the old components were clearly deactivated.
So, in my report I describe what I see, what I can’t see and the potential for latent hazards to exist. Of course, this may apply to many building components so we have to weigh risks. For me, as a HI this merits elevation.
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I agree that it’s a good practice to mention it. In the case of the OP he stated that all of the wiring has been replaced and only the knobs are left, I guess that it should be noted in the report that the K&T is gone.
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IMO… it should be noted in the report that any readily observable indications of active K&T is gone, but may still be present in hidden locations such as walls, attic, basement/crawlspace, etc.
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In such a home I’d look very carefully in each of the junction boxes, particularly those near the main panel, for indication a k&t leg exists. In theory connections from K&T to modern wire are done only in accessible boxes. In practice, weirder things happen.
Maybe pull a light fixture or two from the ceiling, and check what the wires look like. If you’re not allowed to be semi-invasive, look for evidence in the ceilings of patching indicating wire replacement.
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