Knob and Tube Wiring

[goldstar]

Yes, soldered connections are just fine. Especially since if done by the "method of the day", the joint was mechanically secure first (twisted like a wire nut joint would be) then solder was added.

IF. I know it's only two letters long but it's one of the biggest words in our language.

 

[Frank DuVal]

I'll stir the pot.

What is the temperature rating of the conductors used in K&T?

If it is OK to bury 60° Romex in wall and ceiling insulation, what is special about K&T? At least there is just ONE conductor of heat in a given area, not two like Romex (or other brand NM).

I realize 90° has been the standard for years, but there are trillions (I exaggerate) of miles of old 60° NM in walls that are covered in insulation, or get covered in rehabbing houses without a though of danger.

 

[K8MHZ]

I'll stir the pot.

What is the temperature rating of the conductors used in K&T?

If it is OK to bury 60° Romex in wall and ceiling insulation, what is special about K&T? At least there is just ONE conductor of heat in a given area, not two like Romex (or other brand NM).

I realize 90° has been the standard for years, but there are trillions (I exaggerate) of miles of old 60° NM in walls that are covered in insulation, or get covered in rehabbing houses without a though of danger.

Well, I think it's because splices were allowed without boxes in K & T. I see it all the time, anyway. Also, who knows what the temp rating of the K & T conductors were when they were installed?

 

[mopowr steve]

I had, have, a long time customer using one of them on his 480 Pump panels. After I chewed his butt for the second or third time I bought him a Fluke T+Pro and considered it a "free hat" for his years of business.

now back to our program

Although I appreciate your concern, I don't think I would try it on 480v but nothing beats a little neon tester around K+T @ 120v especially when your in a location that does not contain a neutral or ground, and due to inductive pick up on these lines a non-contact tester is about worthless to give an accurate sense of what a K+T wire actually is. Absolutely hands down the best way to figure out "Chicago 3-ways" and other off the wall stuff.
I was taught by an old codger, Sorry.

 

[ptonsparky]

Although I appreciate your concern, I don't think I would try it on 480v but nothing beats a little neon tester around K+T @ 120v especially when your in a location that does not contain a neutral or ground, and due to inductive pick up on these lines a non-contact tester is about worthless to give an accurate sense of what a K+T wire actually is. Absolutely hands down the best way to figure out "Chicago 3-ways" and other off the wall stuff.
I was taught by an old codger, Sorry.

I wasn't concerned, just reminded of a story. I was concerned about my customer.

 

[kwired]

Around here the original service to the older homes was brought to the 2nd floor, sometimes in the stair way, attic, or even a bathroom. Usually a 30 amp service.
As the decades went by, homeowners had more electrical needs and a 100 amp service was put in the basement with the meter socket outside.
That old 30 amp service was gutted and was refed with like four circuits or whatever or completely abandoned.
Basements didn't have any original K&t but maybe a light. As chit was added by that time BX and Emt had came out so that was used.

So that's why around here you normally don't see K&t in panels.

And maybe the installer didn't want to booger up the panel by having knob and tube in it?


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I've also seen old 30 amp still remain in the attic but when they added a 60 or 100 amp fuse panel to the basement, they ran a "load wire" back up the meter riser and attached it to the old 30 amp entrance conductor and left original K&T as is. Don't know if it was code compliant at the time, as you essentially had two service entrances not grouped together, but then nobody was inspecting any of those homes around these parts at that time.

 

[ceknight]

Around here the original service to the older homes was brought to the 2nd floor, sometimes in the stair way, attic, or even a bathroom. Usually a 30 amp service.

One of my customers has her original fusebox still intact and functioning on the 2nd floor. Wood enclosure, even. Many moons ago it was turned into a subpanel and fed from the newer basement service.

Just dug up a photo in case anyone wants to see it: https://dl.dropboxusercontent.com/u/22679567/kt_panel.jpg

 

[mopowr steve]

Are those 30 amp fuses I see on 14 or 12 gauge conductors?

 

[ceknight]

Are those 30 amp fuses I see on 14 or 12 gauge conductors?

At least there weren't any U.S. Mint safety fuses in there.

 

[Pizza]

One of my customers has her original fusebox still intact and functioning on the 2nd floor. Wood enclosure, even. Many moons ago it was turned into a subpanel and fed from the newer basement service.

Just dug up a photo in case anyone wants to see it: https://dl.dropboxusercontent.com/u/22679567/kt_panel.jpg

Nice!
Are they fusing the neutral also?


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[ptonsparky]

Nice!
Are they fusing the neutral also?


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Yes.

 

[ceknight]

Nice!
Are they fusing the neutral also?

Yep.

About the only loads left on that panel are ceiling lamps and some wall sconces. Everything else has been systematically bypassed over time.

 

[al hildenbrand]

I did not ask at the time. On my drive home I thought that I should of because I get a lot of jobs removing knob and tube and it would be great to tell the customer when or if this went into effect.

There has never been a NEC written restriction on K&T conductors or loom entering modern circuit breaker or fuse centers.

There are, however, possibly local ordinances that are involved. My area of work is an inner City Metro of 3 million. The local inner-city electrical ordinances have regulated the exposed length of K&T in unfinished basements and unfinished attics for near half a century. In creating the local ordinance, K&T insulation was deemed subject to undo deterioration when exposed to many basement humidity levels and, similarly, when exposed to the heat of attics. Maximum allowed lengths, under the local statutes, were capped at 18 inches, which was deemed long enough to effect a wiring method change using modern materials and NEC methods.

If the 18 inch length reaches the modern service center enclosure, then it takes less labor and material to go straight into the service center.

And that last line gives, what I think is, the philosophy of most of the historic service upgrade solutions that one sees that others did. Increasing the service capacity of the original K&T service, as noted by others in this thread, most times resulted in the new service center being in a different location, whether just beside or off somewhere in another part of the structure.

Back feeding the old K&T fuses took the least labor and material (as noted by KWired with the example of the "load wire" in the service conduit).

A middle amount of material and labor generally was removing all the fuse blocks, turning the old K&T panel into a junction box, and extending the existing K&T branch circuits to new overcurrent protective devices in the new service center, making the new home runs out of new non-K&T wiring methods.

And, generally, the most labor intensive, back feeding individual K&T circuits by bringing new homeruns to a receptacle box or other location containing both the hot and neutral to effect the transition from a modern wiring method to the original K&T. While labor intensive, this did result in the complete removal of the old K&T fuse cabinet.

Competitive bidding by electrical contractors, and limited-depth pockets of customers, mostly resulted in the buying of the least expensive (think "least labor") solution.

So it was "market forces" not Code that shaped the assemblies we see that upgraded K&T services to newer and bigger services.

 

[al hildenbrand]

Some of the Code limitations on K&T that I've become aware of are:

Since the Eighties, NEC changes, restricting new installation of thermal insulation against K&T, have allowed many insurance companies and insulation contractors to balk at K&T. K&T has a LONG history of being buried in direct contact with old styles of thermal insulation. K&T has not been evaluated for direct contact with foams or insulations including glues, but K&T has a long history WITH cellulose, paper, mica, vermiculite, rock wool, fiber glass, etc. Existing contact with non-foam insulation, that predates the mid-1980s is grandfathered by my AHJs, but no RE-application of insulation to existing K&T is allowed.

Years back, I scoured the early 1900s NECs and learned that most traditional K&T cloth and rubber insulated conductors were either R or RH, which, historically, had 60 degree C or better temperature classification.

 

[grich]

One of my customers has her original fusebox still intact and functioning on the 2nd floor. Wood enclosure, even. Many moons ago it was turned into a subpanel and fed from the newer basement service.

Just dug up a photo in case anyone wants to see it: https://dl.dropboxusercontent.com/u/22679567/kt_panel.jpg

I love the wooden fuse boxes with the asbestos matting lining the inside. Reminds me of my childhood home. There were never pennies behind the fuses, but every fuse was a 30.