Replacing a section of K&T wiring to allow insulation (in California)

[brycenesbitt]

I've got a wall to insulate, but the inspector is asking for 6' of clearance to the knob and tube wiring. The K&T is in good shape and terminates in a single outlet.The general on the job suggest cutting the K&T back to a junction box, then running romex down the wall. Is this a reasonable approach? And if so, it is reasonable to then find a true earth ground and hook up the equipment ground?----------Note: this is California so Article 394 could apply: California permits insulation over K&T with an inspection certificate. This particular house has 12 gauge K&T. The main house feed is three wires with a shared neutral, protected by a 15 amp double pole AFCI breaker. Kitchen & Laundry are on new circuits.Here's a photo of the current outlet (construction date 1938):

 

[kwired]

I've got a wall to insulate, but the inspector is asking for 6' of clearance to the knob and tube wiring. The K&T is in good shape and terminates in a single outlet.The general on the job suggest cutting the K&T back to a junction box, then running romex down the wall. Is this a reasonable approach? And if so, it is reasonable to then find a true earth ground and hook up the equipment ground?----------Note: this is California so Article 394 could apply: California permits insulation over K&T with an inspection certificate. This particular house has 12 gauge K&T. The main house feed is three wires with a shared neutral, protected by a 15 amp double pole AFCI breaker. Kitchen & Laundry are on new circuits.Here's a photo of the current outlet (construction date 1938): View attachment 6895

How impractical is it to just run a new branch circuit? After you go through trouble of getting an equipment ground there you may as well have run new circuit in most cases.

Does inspector want 6' or 6 " of clearance?

 

[fmtjfw]

WOW!

WOW!

That receptacle belongs on a museum. Koooool

 

[brycenesbitt]

6 inches, not 6', that was a typo. And yes of course we could run a totally new circuit... but this one is in rock solid shape. Nice soldered connections, perfect knobs, tubes, unadulterated vintage wiring ready to serve another 75 years.

Can we save it?

 

[kwired]

6 inches, not 6', that was a typo. And yes of course we could run a totally new circuit... but this one is in rock solid shape. Nice soldered connections, perfect knobs, tubes, unadulterated vintage wiring ready to serve another 75 years.

Can we save it?

If it is going to be buried in insulation where no one is going to see it, why do you want to? This is not quite the same as being the owner of a Model T in good condition and wanting to show it off

 

[brycenesbitt]

If it is going to be buried in insulation where no one is going to see it, why do you want to? This is not quite the same as being the owner of a Model T in good condition and wanting to show it off

How about back to the original question: is it code OK to route K&T into a junction box, then complete the stub to an outlet with NM cable?
Does this violate code provisions for "extending" K&T?

Imagine the case where running new wires is too expensive or disruptive to the house or occupants.

 

[kwired]

How about back to the original question: is it code OK to route K&T into a junction box, then complete the stub to an outlet with NM cable?
Does this violate code provisions for "extending" K&T?

Imagine the case where running new wires is too expensive or disruptive to the house or occupants.

That is why there is still a section covering K&T in the code. To enter a box you must enclose the conductor in nonmetallic tubing. I usually run into this problem when trying to re supply a K&T circuit and but not when trying to add additional outlets.

394.10 Uses Permitted. Concealed knob-and-tube wiring shall be permitted to be installed in the hollow spaces of walls and ceilings, or in unfinished attics and roof spaces as provided by 394.23, only as follows:

(1)

For extensions of existing installations

(2)

Elsewhere by special permission

You can extend an existing installation. If you add an outlet that does not relieve you of equipment grounding requirements. If you can get an equipment grounding conductor to the added portion - why can't you get a new circuit there?

 

[brycenesbitt]

If you can get an equipment grounding conductor to the added portion - why can't you get a new circuit there?

In this case there is a nearby ground from a prior generation circuit (two wire tar coated NM cable with bare wire ground).

 

[brycenesbitt]

You can extend an existing installation. If you add an outlet that does not relieve you of equipment grounding requirements. If you can get an equipment grounding conductor to the added portion - why can't you get a new circuit there?

If I cut the K&T, is it OK to terminate the live K&T wires inside the wall? That's how they'd have done it 'at the time'.
If I'm going to drag the stub ends of the K&T into a box, I might as well use them.

 

[ptonsparky]

If I cut the K&T, is it OK to terminate the live K&T wires inside the wall? That's how they'd have done it 'at the time'.
If I'm going to drag the stub ends of the K&T into a box, I might as well use them.

No.

 

[acrwc10]

To insulate over it (in California) most building dept. will want a C-10 licensed electrical contractor to "certify" the K&T as being safe to insulate, in writing. They will make that letter part of the permanent file for that property. Any issue with it in the future and the law suits will be filed against that license holder. So you are now responsible for that 75 year old crap and any future abuse of that circuit.
Sounds like a great idea.

 

[al hildenbrand]

The general on the job suggest cutting the K&T back to a junction box, then running romex down the wall. Is this a reasonable approach? . . . .

Here's a photo of the current outlet (construction date 1938):

View attachment 6895

As I am understanding your question, you are suggesting following the K&T conductor coming out of the top of the receptacle outlet back to where it is first exposed by the wall surface removed during your construction project. There you propose to put a junction box and install a new length of NMB back to the receptacle outlet in place of that exposed length of K&T.

And then you propose doing the same thing again to the length of K&T coming out of the bottom of the receptacle outlet.

Two junction boxes.

And you propose to extend a length of the EGC from another branch circuit to connect to the EGC in the new pieces of NMB.

I don't see a problem, by Code, with this. You've shortened the length of old conductor in an existing branch circuit, you haven't added additional outlets, an EGC is added to the existing receptacle outlet, and the insulation envelope is more complete.

 

[acrwc10]

This is an exaple of how to terminate live K&T in the walls/floors. In this case there was a second floor added to an existing house. The roof was taken off and the K&T was not accessible in many places, so the wire was cut and wrapped around the insulaters twice then wrapped around the conductor 4 more times, then cut and insulated.

 

[acrwc10]

Here is a good reason not to leave it for future use.



The K&T is feeding the NM, not the other way around.