Retention clips on knob & tube, entering metal junction boxes

[brycenesbitt]

Ooh, any code historians? For 1920's era Knob & Tube it was common to see metal clips
used entering metal junction boxes.
Was it required at the time?


I've got an inspector saying the box is fine, but the metal clip need to be retrofitted. I'm fresh out
My concern is the metal clips would hold the loom sheathing from moving when rats run over the wires, but would not prevent the internal wire from moving separately. Thus it seems kind of pointless.
--
Yes I see the roofing nail.
No I'm not involved in any decisions related to replacement of the above wiring.

 

[infinity]

Where is this metal clip in the photo?

 

[brycenesbitt]

Where is this metal clip in the photo?

Missing.
Note the lack of method to secure the wire, as it enters the box.

It appears that in 1920 the installers did not use the metal clip the inspector was looking for.
The inspector said that metal clips needed to be added.

Maybe some Intumescent caulk to keep the mice & insulation out?

 

[Fred B]

Later dates they used the box above that looked very much like a standard MC box thus the extra thick rubber and braid sleeve over the K&O at box entries. Other ones actually had a porcelain grommet that had either a clip or a nut.
These look like it has been modified and altered seeing the porcelain tubes stacked up on a couple of the wires.

 

[hbiss]

The inspector said that metal clips needed to be added.

The guy is an idiot. That wiring has been there for over 104 years and nothing has happened. Then along comes this electrical expert who says that it was done wrong, probably 75 years before he was born.

You are not required to upgrade electrical work that has been inspected and passed when it was installed. Is this guy a home inspector??

-Hal

 

[brycenesbitt]

Is this guy a home inspector?? -Hal

Licensed electrician.
Insurance inspection/insulation.

 

[brycenesbitt]

These look like it has been modified and altered seeing the porcelain tubes stacked up on a couple of the wires.

Those extra tubes are NOT necessarily a modification. They were used back in the day, where wires crossed each other.
They did not depend on the sleeve loom for critical crossings, but rather extra tubes. Basically they assumed the insulation would not last.
True craftsmen, really:

 

[tortuga]

It appears its knob and tube and older NM cable entering that metal box?

Its funny all the different things inspectors use to condemn knob and tube, here the electrical work has to either be up to the code in effect when it was installed or up to the current code.
The most common gotcha I run into with altering existing metal boxes on non-grounded wiring is 314.4, so if you do swap out the box I'd recommend using a non-metallic one.

Ooh, any code historians? For 1920's era Knob & Tube it was common to see metal clips
used entering metal junction boxes.
Was it required at the time?

Do you know what code edition was in effect ?
The short answer is clamp not required per se but conductors need to be rigidly supported within 6" of a splice or tap.

That is a ' junction box' not an 'outlet box' the distinction makes a difference in the old and current code.
A clamp would be required at an 'outlet box' not a junction box.
The funny thing is the 'junction box' itself is not even required, even in the current NEC [300.15].
Box or no box, cable clamp or no clamp your still required to secure the k&t within 6" of the splice [394.30] wich you can accomplish with a cable clamp or porcelain knob to the loom.

 

[infinity]

As an electrician I wouldn't touch that junction box with a 10 foot pole. Like Hal said it has worked for 100 years so leave well enough alone.

 

[brycenesbitt]

As an electrician I wouldn't touch that junction box with a 10 foot pole. Like Hal said it has worked for 100 years so leave well enough alone.

The electrician left the inspection saying the three boxes had to be addressed,
by replacing them with plastic boxes, and modern NM clamps. He estimated an hour of work each.

 

[James L]

The electrician left the inspection saying the three boxes had to be addressed,
by replacing them with plastic boxes, and modern NM clamps. He estimated an hour of work each.

He could end up being there all day

 

[brycenesbitt]

He could end up being there all day

All the better on a T&M job. Other than the rats. Yeah, the rats. Not so nice sharing an attic with them.

--
Consensus above seems to be "do nothing", or "but if you have to do something strap a few cables going into that box and back away slowly and carefully". Then insulate (the AJH supports insulation over inspected Knob & Tube).

 

[James L]

Consensus above seems to be "do nothing"....

I would do nothing as well. Here's how something like that usually goes:

You cut the first soldered joint apart so you can flag those with black or white tape to make sure you get them all back together the same. You bend the wire to put the tape on it, and the cloth turns into dust and falls off the wire. Wire is possibly too short to splice after cutting, too. Now repeat that process.

So now all those wires are too short, and you end up splicing multiple places, then extending with dissimilar wire (cable), and the end product is 10 times worse than if you wouldn't have touched it in the first place.

 

[tortuga]

I would not re-do the box unless absolutely necessary, and if I did anything itwould be non-metallic box.
I have redone lots of boxes like that, the worst ones are lighting outlets that were above 3 100W lights for 75 years those attic or basement ones not as bad .
The damaged k&t I have seen in attics was not due to age of the wire but due to a retrofit of a floor where there was none and a carpenter pulling on the wires or notching joists around them, and/or not being protected from just years of boxes and objects crammed into it.
.

 

[brycenesbitt]

Do you know what code edition was in effect ?

No.
That was in fact the original question: what standard would have applied in the 1920's in California?

 

[JohnE]

Those extra tubes are NOT necessarily a modification. They were used back in the day, where wires crossed each other.
They did not depend on the sleeve loom for critical crossings, but rather extra tubes. Basically they assumed the insulation would not last.
True craftsmen, really:
View attachment 2574750

I've seen hundreds of knob and tube wiring jobs, and have never seen a 'crossing' like that. The individual conductors are usually far more separated and when running along the joist, are stood off with the porcelain knobs.

 

[brycenesbitt]

I've seen hundreds of knob and tube wiring jobs, and have never seen a 'crossing' like that. The individual conductors are usually far more separated and when running along the joist, are stood off with the porcelain knobs.

Maybe it's regional. San Francisco Bay Area the tube crossing like that is all over.
That particular picture is from my home office, about 20 feet from where I'm sitting.

I did see a newer version where loom was used, not a ceramic tube.
But note it's the exact same detail using a scrap of wire to hold the loom in place.
It's the same MWBC trick setup from earlier K&T with nuetral, hot hot, and often wires separated by a full stud bay: