Loom & Panel Box

[daveselectric]

When replacing panels in home wired with knob & tube, we install a 2-1/2" pvc mta as a sleeve for placement of the loom into the panel. The job look neater and does not utilize all the k/o's in the panel. On a recent inspection the inspector said that this was not permitted. I am looking for suuporitng code that allows this type of installation.

 

[al hildenbrand]

Re: Loom & Panel Box

I'm having trouble visualizing your assembly. Are you working on a K&T panel flush mounted in a residential plaster and lathe wall of a wood framed house? Or is it in an open framed wall in an unfinished area? What does your abbreviation "mta" stand for?

 

[daveselectric]

Re: Loom & Panel Box

Al
The loom in question are the home runs at the panel box. We bring them into the panel box thru the center top k/o using a 2-1/2" PVC MTA [Mail Terminal Adapter]

 

[daveselectric]

Re: Loom & Panel Box

Al

The area is usdually an unfinished basement where the service entrance is located.

 

[luke warmwater]

Re: Loom & Panel Box

Are you bringing the grounded conductors through also, and what is the total # of current carrying conductors?
Is the sleeve longer than 24"?

 

[txsparky]

Re: Loom & Panel Box

Although this is a common practice in my neck of the woods, the AHJ can simply argue that the male adaptor is not listed for use with type NM cable. Could you apply Article 312 Cabinets, Cutout Boxes, and Meter Socket Enclosures ? More specifically 312.5 (C) if you used a nipple at least 18" in length.

[ May 28, 2003, 07:32 PM: Message edited by: txsparky ]

 

[russ]

Re: Loom & Panel Box

310.16(B) seems to say, if you have a bushing on the 2 1/2 inch adapter it would be legal.

Russ

 

[txsparky]

Re: Loom & Panel Box

Russ ?

 

[al hildenbrand]

Re: Loom & Panel Box

DavesElectric,

It sounds like the problem is that you only used one mta. TxSparky notes 312.5(C). The NEC Handbook includes an extra explanatory note:

312.5(C) Cables. Where cable is used, each cable shall be secured to the cabinet, cutout box, or meter socket enclosure.
The main rule of 312.5(C) prohibits the installation of several cables bunched together and run through a knockout or chase nipple. Individual cable clamps or connectors are required to be used with only one cable per clamp or connector, unless the clamp or connector is identified for more than a single cable.

The exceptions to 312.5(C) go on. The important one is 312.5(C)ex(c)

A fitting is provided on each end of the raceway to protect the cable(s) from abrasion and the fittings remain accessible after installation.

Essentially, the end of the mta that slides over a conduit is not listed to have cables run in to it.

As a side note, up here in Minneapolis / St. Paul, original exposed K&T in basements is required to be shortened to a maximum of 18" length, converting to another wiring method. It has been determined to be too vulnerable to conditions of a basement.

 

[daveselectric]

Re: Loom & Panel Box

The MTA is less than 2" in hight. All the k & T wires are brought thru the mta. There is no question of bundeling because it is less than 12" in length. Once I figure out how to add a picture to the post, I wll post it.

 

[al hildenbrand]

Re: Loom & Panel Box

Russ,

You meant 300.16(B), yes?

300.16 Raceway or Cable to Open or Concealed Wiring.

(B) Bushing. A bushing shall be permitted in lieu of a box or terminal where the conductors emerge from a raceway and enter or terminate at equipment, such as open switchboards, unenclosed control equipment, or similar equipment. The bushing shall be of the insulating type for other than lead-sheathed conductors.

This goes to the problem, as I see it. The PVC male terminal adapter is only a fitting, without any raceway cemented in it. It is being used as a chase nipple. Without a piece of conduit and a second male terminal adapter the assembly is not a sleeve.