Re feeding knob and tube wiring

[romex jockey]

I wish I had some idea what you mean by any of that.

I wish I could just buy a kit that contains the parts I need to splice the old k&t to a new branch circuit.

Well if you could, it'd be a smaller kit now Mk....

In the past extending it meant extraneous effort running a bond back to the MBJ, water bond, etc

the '14 update made it a tad easier

~RJ~

 

[al hildenbrand]

I run into a lot of old knob and tube wiring in house remodel jobs. I usually just remove it and re wire what it is serving but in this case it feeds a part of the house that is not being renovated. I plan to run a new circuit from the main panel to the knob and tube where it is exposed in the basement but I don't know how to make the transition from Romex to the k&t. What parts do I need to make the splice?

300.16 Raceway or Cable to Open or Concealed Wiring.

(A) Box, Conduit Body, or Fitting. A box, conduit body, or terminal fitting having a separately bushed hole for each conductor shall be used wherever a change is made from conduit, electrical metallic tubing, electrical nonmetallic tubing, nonmetallic-sheathed cable, Type AC cable, Type MC cable, or mineral-insulated, metal-sheathed cable and surface raceway wiring to open wiring or to concealed knob-and-tube wiring. A fitting used for this purpose shall contain no taps or splices and shall not be used at luminaire outlets. A conduit body used for this purpose shall contain no taps or splices, unless it complies with 314.16(C)(2).

This highlighted part of 300.16 is a real interesting one to unpack. It is the basis for the use of the "birds eye" or "monkey face" fittings on the end of old BX armored cable, or old romex, where the cable sheath ends at the fitting and the internal cable conductors continue in free air to the K&T conductors.

I have not found a source for this fitting in today's market.

However, I have used a 1/2" weatherhead with a romex clamp to do the same purpose.

One applies 2014 NEC 394.30(A)(1), and I prefer to do the soldered and taped direct splice.

Regrettably, your inspector sounds to be antagonistic to this part of the Code.

 

[mkgrady]

Well if you could, it'd be a smaller kit now Mk....

In the past extending it meant extraneous effort running a bond back to the MBJ, water bond, etc

the '14 update made it a tad easier

~RJ~

I'm not looking to extend a k&t circuit. I'm looking to demo the parts exposed by removed ceilings or walls and refeeding the inaccessible parts with new Romex.

What 14 code section makes this easier?

 

[mkgrady]

This highlighted part of 300.16 is a real interesting one to unpack. It is the basis for the use of the "birds eye" or "monkey face" fittings on the end of old BX armored cable, or old romex, where the cable sheath ends at the fitting and the internal cable conductors continue in free air to the K&T conductors.

I have not found a source for this fitting in today's market.

However, I have used a 1/2" weatherhead with a romex clamp to do the same purpose.

One applies 2014 NEC 394.30(A)(1), and I prefer to do the soldered and taped direct splice.

Regrettably, your inspector sounds to be antagonistic to this part of the Code.

If he does not allow the new Romex to k&t splice he will in effect be telling me to rewire large sections of the house that there are no plans to remodel. That will cost the customer a lot

 

[GoldDigger]

So you can bring K&T and NM into a box but you cannot splice them together inside that box?
I think the wording of that section could be improved!

 

[al hildenbrand]

So you can bring K&T and NM into a box but you cannot splice them together inside that box?
I think the wording of that section could be improved!

Since the passage lists "box" and "conduit fitting" separate from "fitting", it is my opinion that "fitting" is not being used to describe box in the sentence I highlighted in bold underline red.

To me, the important point is that, since a fitting (terminal fitting) can be used, and the terminal fitting may not have any splices inside it, the language forces the understanding that the exposed internal conductors are to be terminated to the K&T conductors using the standard K&T splicing method (as opposed to being inside a box.)

 

[kwired]

Not that I would do it but technically could I extend the k&t towards the panel utilizing the old knobs and tubes to avoid an extension under 6 feet and avoid the afci protection? Really I would not do this but I'm trying to understand what k&t is usable as is or as modified. The inspector here believe all k&t must be removed once it is exposed. I don't believe that is true.

As some have said - NEC doesn't require it, some local codes may.

metal box with internal clamps, run each of the k&t conductors in each of the holes./QUOTE]

I do not believe this is correct since you did not mention how to deal with the metal between the un-grounded and neutral
conductors. If running the knob and tube conductors through separate holes does not create a situation where there would be metal between the conductors than i am mistaken. If however there is metal between the conductors you would need to cut a slot to allow the magnetic fields to pass through.

For 15 and 20 amp circuits the magnetic fields are not really that significant - but NEC still doesn't specify any particular circuit size either and is written to include all single conductors passing through an individual opening in such an enclosure need slots between holes of other conductors of same circuit.

It's tough to make k&t look existing with used parts. The inspector can believe all he wants, but if it was legal when it was installed it doesn't have to come out for any reason.





I hear you both and I understand, but just about every light fixture ever hung on a knob&tube circuit is hung on a box where the individual conductors run through separate holes in a metal box. Every receptacle resides in a metal box where the conductors come in through separate holes.

Depends on local rules whether exposed old wiring has to come out not the NEC. Not every outlet in these parts has an outlet box where K&T was original method, receptacle outlets typically do, switches typically have a box lighting fixtures often don't have a box, and many original lighting fixtures were not even designed to mount on a box. Some switches weren't designed to mount on a box either, especially the ceramic body rotary type switches.

In Michigan, if a wall is opened (like during a re-mod) all the electrical in that wall must be brought up to current code. It's a Michigan Building Code thing, not an NEC thing, but we still have to do it. So if K&T is exposed during a re-mod here, it must be replaced.

What about a wall that gets opened and no outlets, switches, etc. just old wiring that passes through the space, and maybe on into a space that will not be disturbed?

Actually I seldom remember finding a ?junction? box for ceiling fixture for knob and tube when the wiring method was left in it original condition. Most fixtures supplied by knob and tube wiring methods that I have seen just have the conductors knobbed on the ceiling joist and the conductors just come through a hole in the lath and plaster.

They usually have "loom" (the flexible tubing) around them when passing through wall finish, sometimes even through framing members but usually ceramic tubes through framing members.

The idea behind this wiring method was the conuctors were to be either in contact with an insulating material- knobs, tubes, flexible tubing or were to be suspended between such insulators in free air - they were to never touch other building materials - but back then thermal insulation was not used in the walls like it is today or this method would not have been acceptable in insulated spaces.

 

[K8MHZ]

Iwire:

What about a wall that gets opened and no outlets, switches, etc. just old wiring that passes through the space, and maybe on into a space that will not be disturbed?

Technically, if the wiring is not to today's code, it has to be changed. Luckily, our inspectors are mostly human and would look at the difficulty vs. the safety advantage before making us rip out a single run with no devices. If the conductor showed any damage, that would likely get it ripped out.

 

[kwired]

Iwire:



Technically, if the wiring is not to today's code, it has to be changed. Luckily, our inspectors are mostly human and would look at the difficulty vs. the safety advantage before making us rip out a single run with no devices. If the conductor showed any damage, that would likely get it ripped out.

I'm the one that asked that question.

So how do you connect to old wiring methods that are no longer up to today's standards? You about have to expose some of it in most instances.

Remove wall covering where there is an old panelboard with no equipment grounding conductors in the branch circuit NM cables, all you expose is ~2 feet of cable per circuit between top wall plate and the panelboard - you saying we need to replace those 2 feet of cable in each circuit with a method containing an EGC - what is really gained by this? or worse yet maybe we now have to replace the entire circuit just because we exposed a minimal amount of it even though the project wasn't intended to do anything with the area these cables may run to. Hope that is not the case.

 

[romex jockey]

Iwire:



Technically, if the wiring is not to today's code, it has to be changed.

Mmmmaybe when homes are built with zippered walls ~RJ~

 

[romex jockey]

If he does not allow the new Romex to k&t splice he will in effect be telling me to rewire large sections of the house that there are no plans to remodel. That will cost the customer a lot

Local codes would probably apply Mk

for ex, i just bid on a 3 fam unit here, partial gut. Local AHJ and state codes require complete rewire if over 50% reno.

Now the parts that do not get gutted are simply up for review, either thumbs up/down

The decisive factor being an (or lack of) EGC, juxtaposed with wear/tear, the '14 providing for one more method of doing so

~RJ~