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Knob and Tube.. all got to go? #8977 04/10/02 09:29 PM
Joined: Jan 2002
Posts: 1,457
Electricmanscott Offline OP
Going to check out a job next week. People are buying an old house which of course has knob and tube wiring in there. Their insurance company will not insure unless the wiring is replaced. This is the first time I have ever heard of this. Anyone else. House is in MA.

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Re: Knob and Tube.. all got to go? #8978 04/10/02 10:10 PM
Joined: Dec 2000
Posts: 218
spkjpr Offline
I had never run across that but I personally try to persuade people to remove it. I guess it is ok as long as it's in good shape but it just wasn't ever expected to carry the loads of today. I won't use over a 15 amp if I can't remove it.

Re: Knob and Tube.. all got to go? #8979 04/11/02 08:22 AM
Joined: May 2001
Posts: 129
frodo Offline
as far as i know it is not allowed to extend or modify any existing knob & tube wiring.

additionally most insurance companies will not insure a home with FUSES. i have never seen knob and tube with breakers!

how would you even attach to knob and tube anymore? all splices have to be in a box..right?

i always advise removing the stuff and i will never add to it or repair it. your asking for trouble if you do..



Re: Knob and Tube.. all got to go? #8980 04/11/02 10:56 AM
Joined: Oct 2001
Posts: 597
ElectricAL Offline

Unless there is a wiring mess in the house you are going to look at, I'd suggest the new owners consider getting quotes from other insurance companies. A lot of this confusion comes from loyalty to an Insurance Agent.

I work in Minneapolis / St. Paul and the seven county metro area. The core cities have late 1800 to 1925 housing stock. The original wiring is still in service and in most of the buildings is K&T. K&T's weakness, IMO, is the insulation. Where exposed in basements and attics, humidity and temp cycles degrade the insulation. Over fusing and subsequent overloading will warm the insulation enough, long enough to make it brittle. If it cracks when flexed, it's toast. As long as there is no history of overloading, the K&T in the interior walls has been very stable, in my experience.

I work a lot on old K&T systems and find that it is a sturdy stable (although limited) system that is standing up well under the test of time when not abused.

Splicing of modern wiring can occur at any outlet or light where the unswitched hot and neutral are present. Installing a box at the light may be necessary, as it may not yet have been done. (I've seen my share of modern luminaires supported by drywall screws shot to the lathe.)

Bottom line. . .to the home owners, even if the insurance of existing cared for K&T costs $xx.xx more a year in premiums, how many years of saved premium expense will it take to equal the cost of replacing the existing core wiring system of their new "old house"?


Al Hildenbrand


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