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#213051 - 03/15/14 01:04 PM Terminating AC in a residential style JB
Potseal Offline
Member

Registered: 02/23/13
Posts: 197
Loc: Saskatchewan
The other day I was at a commercial job site where I seen residential type JB's (internal clamps designed for NM cable) being used with BX. The armoured sheath was brought into the JB and clamped. Anti-shorts were used and the end of the armour was wrapped with electrical tape. Never seen BX cable terminated in this manner. Acceptable or poor trade practice?
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A malfunction at the junction

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#213052 - 03/15/14 01:48 PM Re: Terminating AC in a residential style JB [Re: Potseal]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
Not a 'normal trade practice' here as you described. There are (US) j-boxes designed and listed for AC/BX. The internal cable clamp has a 'ring' on the end for the conductors to pass thru, and retain the armour. Some say it is to retain the anti-short.

I have seen that type clamp modified for NM, the NM listed clamps used for AC/BX. And a few terminations with tape.

I would leave a red tag for what you described.
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#213053 - 03/15/14 02:13 PM Re: Terminating AC in a residential style JB [Re: Potseal]
Potseal Offline
Member

Registered: 02/23/13
Posts: 197
Loc: Saskatchewan
Curious...what exactly would the red tag be directed at in your jurisdiction? Would it be the use of a NM clamp on a AC type Cable?

I looked at the CEC 12-610 "Terminating armoured cable" and can't find anything that specifies that the cable can't be terminated with a clamp designed for NM cable. The only rule that mentions the use of a connector or clamp states "shall be of design as to leave the insulating bushing or it's equivalent visible for inspection".

While it looks "wrong" to me I can't seem to articulate as to why.
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A malfunction at the junction

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#213054 - 03/15/14 02:27 PM Re: Terminating AC in a residential style JB [Re: Potseal]
wa2ise Offline
Member

Registered: 11/29/02
Posts: 771
Loc: Oradell NJ USA
Originally Posted By: Potseal
... the end of the armor was wrapped with electrical tape.


The tape would interfere with the ground. The armor and the small ground wire just inside it form the ground, and the box clamp is supposed to contact it and make the ground circuit connection. If the tape was under the clamp, that won't happen and the inspector would red tag it.

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#213055 - 03/15/14 02:27 PM Re: Terminating AC in a residential style JB [Re: Potseal]
Tesla Offline
Member

Registered: 06/16/04
Posts: 1280
Loc: Sacramento, CA
Normally the complaint would be that the gadget is not 'listed' for this particular duty.

In particular, AC & MC connectors specifically have geometries that stop the red hats/ anti-short bushings from falling out (e-tape wrapping is not deemed a substitute) and they also provide a visual gap such as to permit the inspector to see that the red hat has been installed.
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Tesla

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#213056 - 03/15/14 02:35 PM Re: Terminating AC in a residential style JB [Re: Potseal]
Potseal Offline
Member

Registered: 02/23/13
Posts: 197
Loc: Saskatchewan
Ok, finally found a rule that might apply and support the thought that it looks wrong (poor trade practice):

CEC 12-3022 Entrance of conductors into boxes, cabinets and fittings

(5) Where metal-sheathed conductors enter boxes, cabinets, or fittings, the box connector shall be installed in a manner that will meet the requirements of Section 10 without injury to the conductors and shall be the of a type for use with the cable.
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A malfunction at the junction

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#213057 - 03/15/14 02:44 PM Re: Terminating AC in a residential style JB [Re: Potseal]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
My main concern would be the 'tape' you mentioned which may be insulating the bond of the AC armour and the box.

NEC 110.3 (b) "Failure to follow mfg instructions" (not verbatim NEC words) as the NM clamps are for NM, unless they are ID'd for AC, which some are.

Text from the 2011 NEC...
320.40 Boxes and Fittings. At all points where the armor
of AC cable terminates, a fitting shall be provided to protect wires from abrasion, unless the design of the outlet boxes or fittings is such as to afford equivalent protection, and, in addition, an insulating bushing or its equivalent protection shall be provided between the conductors and the armor. The connector or clamp by which the Type AC cable is fastened to boxes or cabinets shall be of such design that the insulating bushing or its equivalent will be visible for inspection. Where change is made from Type AC cable to other cable or raceway wiring methods, a box, fitting, or conduit body shall be installed at junction points as required in 300.15.

I based my previous comments on your description.
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John

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#213058 - 03/15/14 02:44 PM Re: Terminating AC in a residential style JB [Re: wa2ise]
Potseal Offline
Member

Registered: 02/23/13
Posts: 197
Loc: Saskatchewan
Originally Posted By: wa2ise
Originally Posted By: Potseal
... the end of the armor was wrapped with electrical tape.


The tape would interfere with the ground. The armor and the small ground wire just inside it form the ground, and the box clamp is supposed to contact it and make the ground circuit connection. If the tape was under the clamp, that won't happen and the inspector would red tag it.


Concerning bonding/grounding, that thought came to mind but it appeared there was caution taken to keep the taped portion past the point where the clamp met the armour. I don't know why someone would go through the effort for such an installation. BTW, you could still see "some" of the anti-short showing through and therefore could possibly satisfy the rule regarding "visual inspection" of it's presence. Maybe.


Edited by Potseal (03/15/14 02:48 PM)
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A malfunction at the junction

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#213059 - 03/15/14 02:47 PM Re: Terminating AC in a residential style JB [Re: Potseal]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
OK, now that there are other comments that posted while I was typing and cutting and pasting and answering the phone.

Thanks to wa2ise, and Tesla for jumping in.

And Potseal for the CEC article.
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John

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#213060 - 03/15/14 06:27 PM Re: Terminating AC in a residential style JB [Re: Potseal]
Potseal Offline
Member

Registered: 02/23/13
Posts: 197
Loc: Saskatchewan
To expand further on this topic here's a style of junction box that has a built-in connector:



While many of you might be familiar with this type of junction box that can be used with NM or AC type cables I myself have never used such an item.

In the article it mentions not to allow the armour "penetrating into the box". Originally I thought that would be the wording of a rule I would find in the code book. Possibly that's why I thought the installation I had described in the OP looked wrong to begin with.
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A malfunction at the junction

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