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Knob and tube insulation other than rag wrap?


Jeff Beck
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Recent inspection of a vintage house had some knob and tube wiring. I recommended that this be replaced because it was a Safety Hazard and would make getting homeowner's insurance difficult if not impossible.

The seller who is a contractor and flipper has tried several times to convince the buyers that this isn't a problem. The more he tries the more concerned the buyers become.

Today he called to say that he had an electrician inspect the knob and tube wiring. The electrician said the wiring was all right and the only reason to replace it was for aesthetics.

I reviewed my pictures taken at the inspection and found this one.

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On second look it does seem that the wiring has an insulator other than rag wrap.

Am I wrong in recommending that it be replaced?

Jeff Beck

Foresight Inspection

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Jeff,

I don't think you were wrong. Our job is to protect our clients. By telling them that they have old and outdated wiring system, you are protecting them. The cost of rewiring a home is substantial. Just offer your clients your opinion, back it up with some research data and leave it at that. Most electricians will tell you that there is nothing wrong with Knob and Tube, the issue is what has been done to the wiring over the years. That and the fact most insurance companies won't insure it.

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I think I see rubber insulation with a cloth cover, maybe a bit thicker than usual. We know that the rubber breaks down and becomes brittle. No ground path to any of the receptacles or fixtures. Probably antique switches and outlets.

You are right to call for replacement, IMO. That would be best practice for your client. Now an electrician has taken responsibility for the wiring. Hopefully that is in writing, because your clients need to find insurance. At least you are on record saying it is unsafe.

Someday, your clients will want to sell. Will the wiring still be OK? At some point, somebody will have to bite the bullet and replace at least the bad sections.

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You made the right call, assuming your report wording didn't say things it shouldn't. But, yes, replace the darn stuff; it's old, and ungrounded/not as safe as today's wiring. People insulate over/around it and exacerbate the hazards posed by such. Good advice to replace.

Two other things, though...

How's the leg coming?

How come Robert ain't yet convinced about Da Bears?

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I would be sure and let the client know it exists and the cons (no equipment grounding conductor, insurability, and the fact you're not supposed to insulate over it, etc.), but I wouldn't tell them that it needs to be replaced outright if it otherwise appears to be in good condition.

Usually these old wiring systems are hobbled by a bunch of DIY taps and splices. Sometimes the insulation is disintegrating or has been muched on by rodents. The problem is usually not the wire, but the insulation.

Chris, Oregon

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To add to the reasons for scrapping this particular knob & tube installation, that junction box has a few problems. The individual conductors are not allowed to go through separate holes. All of the conductors of each circuit have to go through one common hole, otherwise there is a problem of inductive reactance and heating at the hole in the metal box. An alternative is to cut a slot between the holes for each circuit's conductors. It's not likely to cause a big problem at the levels of current drawn by house circuits; nonetheless - it indicates substandard workmanship. I guess the electrician thinks that compliance with NEC 300.20 is just an irrelevant "aesthetic" issue.

And to pile on a bit more, the splicing technique inside the box is pretty bad. They have also used the wrong ceramic bushings, and the loom (the rag tubes) should fit into the bushings.

Another problem with knob and tube (at least around here) is that it almost always contains multiwire circuits with undersized neutrals. They will run 12 for the red and the black, and 14 for the white wire. It should be fused at 15 amps in such cases.

Douglas Hansen

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Is there any documentation to back us up on the "insurance company won't write you" statement?

I've seen this written a number of times before, but I hesitate to repeat it without something to fall back on.

Are they all on board with this, or are the percentages different from one insurance carrier to the next?

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Is there any documentation to back us up on the "insurance company won't write you" statement?

I've seen this written a number of times before, but I hesitate to repeat it without something to fall back on.

Are they all on board with this, or are the percentages different from one insurance carrier to the next?

Hi,

The first 8 years I was in this business I never heard a complaint from any clients about their insurance companies refusing coverage. Then, somewhere around 2004, I had a couple of complaints in quick succession from clients who'd been refused coverage because there was K & T in the house. Since then, I recommend they get rid of it or expect either not to be able to get coverage or end up paying more because of it.

ONE TEAM - ONE FIGHT!!!

Mike

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Is there any documentation to back us up on the "insurance company won't write you" statement?

I've seen this written a number of times before, but I hesitate to repeat it without something to fall back on.

Are they all on board with this, or are the percentages different from one insurance carrier to the next?

This isn't something you can predict. Even the same insurance company might accept a home with K & T on Monday and reject the next one on Tuesday.

The most you can say is that some insurance companies might decline to insure homes with a substantial amount of K & T wiring.

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Yesterday's inspection had K&T but also had an abundance of NM w/G throughout. I'm guessing that the K&T wasn't live anymore but I'm not sure. Just curious...What's the wording of the question from the insurance company about K&T? They want it physically removed from the premises or just disconnected from all voltage?

Marc

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From what I hear from the insurance guys that I know, it depends on if you're already a client or applying for insurance .

Most underwriters prefer that it be removed but some of the smaller companies will take having it disconnected and certified by an electrical contractor.

One of my friends also told me that if it is just disconnected that the premiums will be higher. I'm not sure that makes sense but ultimately it's just all about the money anyway.

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Yesterday's inspection had K&T but also had an abundance of NM w/G throughout. I'm guessing that the K&T wasn't live anymore but I'm not sure.

A $15 voltage sniffer will tell you if it's live. However, if it is clustered with other live wiring, you can easily get a false live reading. Also remember only half the K&T wiring will be hot, the other half are neutrals. So you want to look for a parallel feeder if you find one wire that appears to be dead.

AFAIK, the insurers don't care what you do with the old wiring as long as it is not going to cause trouble for them.

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tn_20101241516_KT%20test.jpg

52.74Â KB This one was live, in a 5 foot basement.

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Almost every home that has K&T has had some upgrades at one time or another. The one I find most often is the addition of insulation all over the house. Blown into the attic, tucked into the floor joists and blown into the walls. Once the K&T is buried with insulation, it is a fire issue. Time to upgrade. The price goes way up when the replacement takes place and you have to meet current codes.

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Just curious...What's the wording of the question from the insurance company about K&T?

Q: What year was the house built?

A: 1870.

Q: What is it made of?

A: Wood, plank framing.

Q: Is there any K&T?

A: No.

My house was plumbed for gas lights. It had indoor plumbing early, the septic system I replaced was built in 1896. It wasn't wired though until very late, 30 amp, 120 volt service that was all tin coated copper. My guess is around 1940 cause the meter looked like a mantle clock perched atop the main panel. Two circuits in the main and four more in a sub. My Makita circular saw would dim the lights, and blow fuses if I was running anything other than a few light bulbs.

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John,

I think that's true to a certain extent but not always.

The insurance guys that I've talked to about this pointed out that if the K&T has been disconnected but not removed and there is a subsequent fire that's not K&T related, and the adjuster/investigator sees the K&T, they may use that to deny the claim. This leads to subsequent reviews and possibly a lawsuit which is why they want to charge more if the K&T remains.

Companies the size of Allstate and State Farm have people who do nothing but think up ways to avoid spending money on claims.

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John,

I think that's true to a certain extent but not always.

The insurance guys that I've talked to about this pointed out that if the K&T has been disconnected but not removed and there is a subsequent fire that's not K&T related, and the adjuster/investigator sees the K&T, they may use that to deny the claim. This leads to subsequent reviews and possibly a lawsuit which is why they want to charge more if the K&T remains.

Companies the size of Allstate and State Farm have people who do nothing but think up ways to avoid spending money on claims.

Thanks, good point. After the blaze, it could be hard to prove the old wires were not responsible, and easy to claim they were.

Hopefully there would be copies of invoices from the upgrades. But around here quite often there will be sections of K&T still in use in the hard to reach areas, in the plaster ceilings between floors, for example.

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Isn't there some component of the NEC that indicates old and abandoned wiring should be removed as part of any alterations?

I recall this coming up in one of my muni gigs, when a state arson investigator was teaching a class I was taking.

Anyone know if that's accurate, or folklore? (I don't know where to look in the NEC.)

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As a contractor, I had a few jobs rewiring a house with commercial wiring methods because the area was re-zoned commercial or because it was relocated to an area zoned commercial. The AHJ would tell me to simply cut out all NM flush at the entry into the boxes. No need to remove wiring that lay within the walls or hidden spaces.

Marc

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I'm guessing that the K&T wasn't live anymore but I'm not sure. ...Marc

Marc, you couldn't make a determination whether the visible K & T was live or dead?

I have a couple of the voltage sticks, but they just don't seem reliable. I prefer to use my 25 year old Tic Tracer; still works like a charm.

I could not positively confirm that all K &T was removed from circuit. I used non-contact testers for many years as a contractor but do not rely on them as an inspector.

I'll have to check out this Tic Tracer.

Marc

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Isn't there some component of the NEC that indicates old and abandoned wiring should be removed as part of any alterations?

I recall this coming up in one of my muni gigs, when a state arson investigator was teaching a class I was taking.

Anyone know if that's accurate, or folklore? (I don't know where to look in the NEC.)

There is but it applies to LV like phone and data cables.

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