Older house wiring puzzle

What is Knob and Tube Wiring March 8, 2008 =B7 Filed Under Home Inspections and Home Maintenance I=92ve recently witnessed knob and tube wiring in some downtown St. John=92s homes. It=92s not a common sight, but when things are uncommon and unknown a lot of questions arise.

So, just what is knob and tube wiring?

Knob and tube wiring is found in older homes dating back to the

If you happen to notice knob and tube in a home you are purchasing (hopefully you have a Home Inspector) asks lots of questions.

In the =93older days=94, this method was quite adequate for the electrical loads being produced in a house hold. However as computers, plasma TV=92s and microwaves became the new way of life, the increase is amperage (electrical current) to run these devices posed a problem for knob and tube wiring. It became subject to repeatedly blowing 15mp amp fuses. Quick fixes allowed homeowners to over-fuse circuits (changing the 15amp fuse to a 20 or 30amp fuse) which in turn caused heat damage to the wiring due to higher levels of current.

Some insurance companies in St. John=92s will still insure knob and tube wiring but they require an electrician to inspect the house to make sure that there are no circuits over-fused. Of course there are some insurance companies in St. John=92s that refuse to insure knob and tube wiring. No insurance =3D no mortgage.

Tags: downtown St. John's, electrical, home inspector, homeowner, knob and tube

Connections to concealed knob-and-tube wiring. In cases where the existing wiring is concealed knob-and-tube, the NEC does allow it to be extended from an existing application. But that is seldom practical because the hardware is no longer readily available, and the existing knobs salvaged from old jobs have internal spacings for old Type R conductor insulation that will not work on today=92s thinner insulated conductors. Concealed knob-and-tube, as a wiring method, has no equipment grounding conductor carried with it. Over the generations, NEC provisions have changed to the point that it is almost impossible legally to wire anything without grounding it. For example, until the

Meanwhile, grounding has been getting more difficult to arrange to remote extensions of concealed knob-and-tube outlets. Until the 1993 NEC, you could go to a local bonded water pipe to pick up an equipment grounding connection, and then extend from there with modern wiring methods. Now 250.130(C), which governs this work, requires that the equipment grounding connection be made on the equipment grounding terminal bar of the supply panelboard, or directly to the grounding electrode system or grounding electrode conductor. You will not be inspecting grounding connections associated with concealed knob-and- tube wiring in a steel-frame building. Rather you will see this in old wood-frame buildings, probably residential. In such occupancies, even if the water supply lateral is metallic, the water piping system ceases to be considered as an electrode beyond 5 feet from the point of entry. This usually means fishing into the basement. If the contractor can fish a ground wire down to this point, he or she can fish a modern circuit up in the reverse direction and avoid the entire problem.

It is true that some geographical areas have more extensive use of slab-on-grade construction, and here interior water piping is sometimes permitted to qualify as electrodes because the pipes extend to grade for the minimum threshold distance of 10 feet, and thereby allow interior connections. But in almost every case, extensions of concealed knob-and-tube wiring do not do well upon close inspection.

In addition to the grounding issue, beginning with the 1987 NEC this wiring method cannot be used in wall or ceiling cavities that have =93loose, filled, or foamed-in-place insulating material that envelops the conductors.=94 This effectively means that such cavities cannot be insulated, because the only method of compliance involves opening all the walls to install board insulation products, and no contractor is going to keep this wiring method with the walls open. This rule is particularly controversial because, to the extent enforced in existing construction, it is a powerful economic disincentive for owners to retrofit thermal insulation.3

bud I copied and pasted because obviously you are too lazy to click on links, while you spout dis information it just adds to readers confusion.

this is just a few of the references. who wants a obsolete system that shouldnt be insulated?

few homebuyers will be interested in buying such a home.

rewiring isnt that expensive, when you consider how it increases your homes value.

besides if a homebuyer cant get homeowners insurance its a no sale...... for nearly every buyer out there.

so the seller must rewire, at that point the rewire must meet all current safety codes...............

bud you want a 100 more? or a 1000?

just to discredit you i nwill be happy to keep on posting.:)

Bud now knows I am correct:) The K&T issues are well documented, everything from insulation being a bad idea, to insurance troubles. besides lack of grounds and being obsolete.

Bud glad i was able to help educate you:)

My "dreamland" is based on years of experience as an electrician. Much of it was doing service calls where I saw numerous K&T installations.

I believe Roy, another electrician, has also written K&T that has not been abused is not a problem.

halerb had a nightmare where he was attacked by knobs and was forced to hide in tubes.

To look at claims of K&T hazards:

Over fusing is a problem for any wiring method. One could argue that K&T is more immune in that wires are not in contact with each other until they reach a box.

I have seen no evidence of problems in attic wiring. I have salvaged wire out of attics that was in like-new shape.

Heat at ceiling lights can certainly rot out insulation. It rots out

"Critters" can be a problem for Romex.

None of these problems are unique K&T hazards.

As posted previously

There is no reason to believe "insulation on top of knob and tube wiring is a major fire hazard". This is home inspector FUD. Where is the supporting data.

bob haller wrote: >

The only K&T hazard in the post - as already stated, over fusing can be a problem for any wiring system. This is not a specific K&T hazard.

Again looking at

As I have already pointed out, there is no *data* to support the claim that the insulation causes a hazard. The chief electrical inspector for Minneapolis has said insulation was not a problem.

Too lazy - I am devastated. (Have you read my sources?)

My "dis information" came from state agencies and electrical inspectors.

Two of your sources were apparently home inspectors. Two of your sources were completely unidentified.

I want to see a knowledgeable electrical industry source, not home inspector FUD.

In the real world, rewiring to completely eliminate K&T is enormously expensive.

Where is the insurance casualty *data* that justifies insurance denial. Still missing.

Just as it was missing when challenged in Maine and the insurance company "provided no justification for its position that knob and tube wiring per se automatically provides grounds for nonrenewal".

You appear to have no concept of what the NEC requires. A "rewire" only affects the wiring that is changed. A "rewire" does not require all wiring in a house conform to the current NEC. You are really a fount of misinformation.

As I have said, you can "rewire" and leave the existing K&T.

Of course, just like a Jehovah's Witness.

Still missing - *data* that supports your claim. Your buddies at State Farm can't help you?

Bud ignores the NEC, which prohibits insulation contacting K&T

jeez i wouldnt want to live in a home you worked on.........

you must believe the NEC is advisory only?

you must be smarter than the entire NEC, which must look at all these issues carefully

it does if homeowners insurance REQUIRES its removal and once the homeowner faces that it requires things like GFCIs

the NEC must be a nuisance to you, soft shoe shuffling past safety cdes and requirements

You haven't proved or educated anyone you pin headed bastard. No links, no official docs, just a bunch of made up text that had no conclusive results.

The NEC does not regulate the insulation of houses. AND the K&T wiring is not new enough to be involved in a current inspection process. I've covered miles of it with insulation in multiple rentals. Proper fusing of the circuits is the key. No overamperage= No heat. You should just go hang yourself with some single strand wire you pin headed bastard.

The insurance DOES NOT require the removal of it. And you have not provided any documentation to the effect that it does.

many insurance companies REFUSE to write NEW policies on homes with K&T wiring.

OK its time i flood this discussion with info

In 1987, the National Electric Code prohibited the placement of insulation in contact with this type wiring. Later, a couple of west coast states permitted insulation provided the wiring was "certified" by a licensed electrician, foil or paper backed batt insulation was not used and warning signs were placed where the old wiring is concealed by the insulation.

=BDYou should just

Currently the United States NEC forbids use of loose, blown-in, or expanding foam insulation over K&T wiring.[5] This is because K&T is designed to let heat dissipate to the surrounding air. As a result, energy efficiency upgrades that involve insulating previously uninsulated walls usually also require replacement of the wiring in affected homes.

you must be buds realtive or something:) your rentals are at some risk from fire.......

you need to check current codes, but heres the wikipedia reference

make sure it's reliable info with links.

I'm not worried about your so called "codes" and i'm CERTAINLY not reading ANYthing from MF wikipedia.

The only thing I have ever found wrong with K&T is that it is getting close to 100 years old . Not just the wiring but the insulators and the framing they are attached too and the fasteners they are attached with. Almost all problems I have seen with it are due to age. A lot of things happen in years. Wood shrinks, nails rust, insulators crack, all it takes is time for something to go wrong. If the argument is that there is still plenty of K&T that looks like the day it was installed I would agree but I would have to ask, "for how much longer".

The only code I know of that specifically addresses K&T is a local code that forbids the repair and modification of K&T wiring.This pretty much means if it breaks or you touch it rip it out. I first became aware of this when helping my then fiance to restore her Victorian farmhouse around 1982. Switch wiring mounted externally on a wall which we had taken down while making repairs to the wall could not be replaced. We were able to get around this by letting the K&T become a low voltage control circuit for her lights. Under this code the updating the breaker panel forced the removal of all of the K&T with the exception of the part we used for low voltage.

Jimmie

NEC 394.12 2002 specifially prohibits insulating K&T in wall cavaties

geez its near a 100 years old, everything needs replaced eventually.

shingle roofs 25 years

I'm likely going to raise the ire of some home inspectors on this group, but I've found them, on the whole, to be a pretty clueless bunch.Many "minor issues" identified are actually pretty expensive and serious shortcomings, while many "serious issues" are simple maintenance items that can be easily remedied at low cost. And many quite major issues are totally missed.

Actually, in many cases , done as part of a redecoration job to get a house ready to sell (improve curb appeal, make it "show well", the cost to totally rewire to current code is SURPRISINGLY affordable. Particularly if the house has both an accessible attic and a full basement. It's incredible how little plaster/drywall really needs atro be damaged/opened up to rewire an older home. The only thing not "to code" would be the spacing of "handy-straps" holding the cable to the studs. The extra wire needed to do it the "simple" way is much less expensive than the extra labour etc to do it the "hard" way.

Yup - but the FACT is, you still cannot buy NEW insurance on a home with K&T wiring in the vast majority of both the USA and Canada.

Renewals are still (generally) available - but no "new business"

In many cases you can leave K&T by code, but in those same cases you may STILL not be able to write new insurance policies on the home.

A friend's son bought a home less than 10 years ago that was advertized as fully rewired and re-plumbed.

When he went to sell 2 months ago, a home inspector found there was still K&T in use throughout most of the main part of the house, as well as a lot of galvanized water pipe and the cast iron sewer stack (which was rusted through and leaking in several spots)

When that was discovered, it had to be told to all prospective buyers

- which severely limited the market, and the price he could expect to get for the house.

After getting some estimates they dropped the price something like $30,000 and it was snapped up almost immediately - the buyer knowing the wiring and plumbing could be brought up to current code, with all iron pipe and K&T wiring replaced, and redecorated for that amount, with money left over. (House listed for $285,000)