Knob and tube connector

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JJWalecka said:
Is there a listed knob and tube connector for bringing knob and tube into a panel board?
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To connect to a panel you will have to sleeve the conductor in order to go to less than a three inch separation. . . what about this?

Attic%20box%20mockup%202%20Cropped_zpswxwexmcq.jpg
 
al hildenbrand said:
To connect to a panel you will have to sleeve the conductor in order to go to less than a three inch separation. . . what about this?

Attic%20box%20mockup%202%20Cropped_zpswxwexmcq.jpg
Click to expand...
Is that NM cable sheath?

If so that is creative, don't know how easily it would be approved by an inspector.

However one does it, you need to bring all conductors of a circuit through same hole in a ferrous enclosure or cut slots between the holes so you effectively only have one hole to minimize inductive effects.
 
kwired said:
Is that NM cable sheath?

If so that is creative, don't know how easily it would be approved by an inspector.
Click to expand...

I agree that the assembly in the photo above is quite interesting. There is a lot of understanding going on in the assembly, in my opinion.

I'm pretty sure that it is NM cable sheath. Let's say that, in fact, it is. . . what is "un-approvable", by NEC rule, about it?
Article 394
Concealed Knob-and-Tube Wiring
394.19 Clearances.
(A) General. A clearance of not less than 75 mm (3 in.) shall be maintained between conductors and a clearance of not less than 25 mm (1 in.) between the conductor and the surface over which it passes.
(B) Limited Conductor Space. Where space is too limited to provide these minimum clearances, such as at meters, panelboards, outlets, and switch points, the individual conductors shall be enclosed in flexible nonmetallic tubing, which shall be continuous in length between the last support and the enclosure or terminal point.
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I'm sincerely asking.

I've just crawled through the White Book and the NFPA Glossary, and, of course, the NEC, and I'm finding, I believe, that "flexible nonmetallic tubing" is undefined.
 
al hildenbrand said:
To connect to a panel you will have to sleeve the conductor in order to go to less than a three inch separation. . . what about this?

Attic%20box%20mockup%202%20Cropped_zpswxwexmcq.jpg
Click to expand...



kwired said:
Is that NM cable sheath?

If so that is creative, don't know how easily it would be approved by an inspector.

However one does it, you need to bring all conductors of a circuit through same hole in a ferrous enclosure or cut slots between the holes so you effectively only have one hole to minimize inductive effects.
Click to expand...

al hildenbrand said:
I agree that the assembly in the photo above is quite interesting. There is a lot of understanding going on in the assembly, in my opinion.

I'm pretty sure that it is NM cable sheath. Let's say that, in fact, it is. . . what is "un-approvable", by NEC rule, about it?

I'm sincerely asking.

I've just crawled through the White Book and the NFPA Glossary, and, of course, the NEC, and I'm finding, I believe, that "flexible nonmetallic tubing" is undefined.
Click to expand...

Imo, there is nothing wrong with using those scraps to wrap K&T as shown in the pic- it gets done all the time. If that gets failed, then the inspector needs his head examined- who would have an issue with protecting a few inches of 90 year old RW conductors with a good layer of plastic, the same plastic that is considered perfectly fine to wrap the wires installed in millions of newer homes.:happyno:

I have heard before that "flexible nonmetallic tubing" in the context of 394 refers to loom-I have no proof that that is the true definition, just what was heard. One could use loom if they could find it, but really what would be the benefit of doing that vs the nm jacket scheme or even heavily wrapping the wire in several layers of tape?
 
Never seen that done before, but like the idea better then some things I have seen done.

I still have to wonder how many inspectors will approve it.

I have also always assumed flexible nonmetallic tubing mentioned to be the product that is designed for that purpose, and not just any tubing you can find. I have re-used old loom at times in the past, don't know if there is any availability of a new equivalent tubing out there or not.
 
I have used both heat shrink and clear plastic tubing.
Both of which are non metallic and flexible, and the word "tubing" is in one of them!:)
 
user 100 said:
I have heard before that "flexible nonmetallic tubing" in the context of 394 refers to loom-I have no proof that that is the true definition, just what was heard.
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In my experience, "loom" is, in fact "flexible nonmetallic tubing" as used in NEC Article 394.

I checked one more place and found this:
IEEE 100
The Authoritative Dictionary of IEEE Standards Terms
Seventh Edition
flexible nonmetallic tubing (loom) A mechanical protection for electric conductors that consists of a flexible cylindrical tube having a smooth interior and a single or double wall of non-conducting fibrous material. See also: raceway.[/b]
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The sheath on NM-B is definitely evaluated (by NRTLs) for the mechanical protection of the insulated conductors within the sheath, it is non-conductive, and it is flexible. One can quibble over whether 12/2 sheath is exactly cylindrical, and whether "fibrous" is required.
 
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I also find it interesting that putting "wire loom" or "flexible nonmetallic tubing" into a search engine brings a LOT of results.

A lot of the search engine returns are commonly aimed at the automotive industry, but there is obviously a lot of application for all manner of use with all manner of wiring. . . just saying.

Personally, I've always managed to have a stock of early 1900s "fibrous" loom that has satisfied my needs in the field. I will find old specimens of loom in wiring demo and save the good flexible lengths for reuse.

Until I bumped into the assembly in the photo above in this thread, I had never really given thought to how I would handle running out of my small stock of historic loom. I believe that the use of NM sheath is a really smart use of a contemporary product for an historic wiring method mechanical protection.
 
al hildenbrand said:
I also find it interesting that putting "wire loom" or "flexible nonmetallic tubing" into a search engine brings a LOT of results.

A lot of the search engine returns are commonly aimed at the automotive industry, but there is obviously a lot of application for all manner of use with all manner of wiring. . . just saying.

Personally, I've always managed to have a stock of early 1900s "fibrous" loom that has satisfied my needs in the field. I will find old specimens of loom in wiring demo and save the good flexible lengths for reuse.

Until I bumped into the assembly in the photo above in this thread, I had never really given thought to how I would handle running out of my small stock of historic loom. I believe that the use of NM sheath is a really smart use of a contemporary product for an historic wiring method mechanical protection.
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I couldn't find any with a smooth interior, let alone a fibrous wall along with that. I know exactly what the stuff is, I have seen lots of it.
 
al hildenbrand said:
Google "braided wire loom" or / and look at Cable Ties and More's page.

Given the synthetic cloth we wear in various ways as clothing, nylon, rayon, polyester, etc., a woven plastic fiber, I think that the term "fibrous" is satisfied.
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The stickler, if one was to be technical, is the 'smooth inside'. The link I put up offered asphalt coating inside and out (as an option), which would be 'smooth' in my opinion. Otherwise, there are several places that sell woven wire loom for antique car and motorcycle applications with exposed fiber for an interior.
 
K8MHZ said:
The stickler, if one was to be technical, is the 'smooth inside'.
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I believe that is a verbal hall-of-mirrors that one can be distracted by. . . smooth at a quantum level? smooth at a molecular level? How far to go. . .

Well, if the insulated conductor can slide into the length of loom required for the physical protection needed to satisfy Article 394, isn't that adequately smooth? The looms we are looking at are definitely free if burrs and sharp cutting edges or other protrusions that would damage the conductor insulation, in my opinion.
 
JJWalecka said:
Is there a listed knob and tube connector for bringing knob and tube into a panel board?
Click to expand...
I realize I haven't directly addressed your question. I, initially, couldn't think of a connector that I knew had a rating for "knob and tube".

Then I realized, I don't think there has ever been a connector so rated. . . Here's why. The insulated conductor was commonly an R, RH, RHH, RW, RHW, or even an RHHW and either entered enclosures through an insulating bushing, or entered an enclosure's knockout hole sleeved in loom (flexible nonmetallic tubing). In all the historic assemblies I've worked around or with, there has never been a "connector" used. . . with one exception.

The exception is fished in loom to a rework metal wall case, used for either a switch or receptacle. The loom, upon entering the wall case would be clamped by an internal wall case clamp, or, in some manner, secured to prevent the loom from sliding back out of the wall case. I've seen friction tape used to make a "bell end" on the end of the loom inside the wall case, I've also seen slide on retaining clips put on the loom that have little biting points that secure to the loom. There are undoubtably other tricks that were used.

In practice, I've liked using nonmetallic cable clamps that are rated for 12/3 or two 12/2s. But, squeezing two loom sleeves into them is not practical, and cutting slots between adjacent holes is awkward, let alone, a waste of the limited number of K.O.s.

Technically, strapping down the loom protected K&T conductor within 12" of the loom going through the naked K.O. is adequate for Article 394, in my opinion. One can place two loom covered K&T conductors through a raw, unbushed 1/2" K.O. in most cases.
 
al hildenbrand said:
I believe that is a verbal hall-of-mirrors that one can be distracted by. . . smooth at a quantum level? smooth at a molecular level? How far to go. . .

Well, if the insulated conductor can slide into the length of loom required for the physical protection needed to satisfy Article 394, isn't that adequately smooth? The looms we are looking at are definitely free if burrs and sharp cutting edges or other protrusions that would damage the conductor insulation, in my opinion.
Click to expand...

That would be an AHJ call, obviously.
 
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