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#96226 - 11/10/05 09:59 AM Bushings on RMC
cubby964 Offline
Member

Registered: 10/18/02
Posts: 69
Loc: USA
Hello Guys and Gals:

Just wanted to see what the prevailing opinion is concerning 2005 NEC 344.46.

I feel this states that all RMC entering a box, etc. requires a bushing. This is also the way I have always installed RMC.(even when it was called GRC

Several other inspectors disagree and believe the FPN referring to 300.4(F) indicates this is only true for #4 and larger.

I believe the Code panels do not repeat themselves and the FPN is simply a way to give additional information regarding wires #4 and larger and has nothing to do with the requirement for bushings on all RMC.

FWIW The situation is a new installation with multiple 3/4" RMC stubs into the bottom of several panels. The number is close to 50, so it would be a large amount of re-work to install the bushings as these panels are hot and the building is almost ready for occupancy.

Thanks,

Jim

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#96227 - 11/10/05 01:03 PM Re: Bushings on RMC
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
Jim I agree with you.

 Quote:
344.46 Bushings.
Where a conduit enters a box, fitting, or other enclosure, a bushing shall be provided to protect the wire from abrasion unless the design of the box, fitting, or enclosure is such as to afford equivalent protection.


It seems pretty clear to me that all RMC will have bushings regardless of wire size.

The same can be said off RNC.

 Quote:
352.46 Bushings.
Where a conduit enters a box, fitting, or other enclosure, a bushing or adapter shall be provided to protect the wire from abrasion unless the box, fitting, or enclosure design provides equivalent protection.


and IMC

 Quote:
342.46 Bushings.
Where a conduit enters a box, fitting, or other enclosure, a bushing shall be provided to protect the wire from abrasion unless the design of the box, fitting, or enclosure is such as to afford equivalent protection.


I can't see how these sections could be misunderstood.
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

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#96228 - 11/10/05 01:34 PM Re: Bushings on RMC
winnie Offline
Member

Registered: 09/15/03
Posts: 652
Loc: boston, ma
As I read it, a bushing is required for _all_ RMC entering a box, but that for conductors #4 or larger a smoothly rounded _insulating_ surface must be provided. Presumably a _conductive_ bushing is permitted for conductors smaller than #4 as long at it appropriately protects the insulation.

Of course the font of all knowledge (google) provides a discussion of the solution in Mike Holt's forum: http://www.mikeholt.com/cgi-bin/codeforum/ultimatebb.cgi?ubb=get_topic;f=11;t=008514;p=

Arlington Adjustable Throat Liner http://www.aifittings.com/m_6.htm

-Jon

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#96229 - 11/29/05 11:51 AM Re: Bushings on RMC
cubby964 Offline
Member

Registered: 10/18/02
Posts: 69
Loc: USA
The head electrical inspector for this state(not mine) has determined that bushings are not required for smaller than #4.

Everyone else I spoke with about this agrees with us.

Thanks for the confirmation, guys!
Jim

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#96230 - 11/30/05 05:49 PM Re: Bushings on RMC
Tesla Offline
Member

Registered: 06/16/04
Posts: 1280
Loc: Sacramento, CA
The #4 threshhold is specifically for EMT and other such raceways.

RMC, IMC, etc. require bushings up and down their range: there are no exceptions: 344.46.

300.4F Handbook detail lays this all out.
_________________________
Tesla

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