Concentric knockouts on circuits over 250 volts [RE-wrenches]

[Bob-O Schultze, Electron Connection]

<x-flowed>

William,
If I read this right, this only applies to situations where one is  
using the EMT or the like as the grounding conductor. Where one  
carries a grounding conductor from the PVs down to the DC disco and  
it is bonded to all the metal boxes using a lay-in lug or the like, I  
don't see the need for the bonding bushings. Just my thoughts, I  
could be wrong.
Bob-O
On Aug 27, 2006, at 12:18 PM, William Miller wrote:

>
> Friends:
>
> It has come to my attention that bonding bushings are required in  
> our DC feeder conduit where it enters the DC disconnect via  
> concentric knockouts per NEC:
>
> 250.97 Bonding for Over 250 Volts.
> For circuits of over 250 volts to ground, the electrical continuity  
> of metal raceways and cables with metal sheaths that contain any  
> conductor other than service conductors shall be ensured by one or  
> more of the methods specified for services in 250.92(B), except for  
> (1).
> Exception:  Where oversized, concentric, or eccentric knockouts are  
> not encountered, or where a box or enclosure with concentric or  
> eccentric knockouts is listed for the purpose, the following  
> methods shall be permitted:
> (a) Threadless couplings and connectors for cables with metal sheaths
> (b) Two locknuts, on rigid metal conduit or intermediate metal  
> conduit, one inside and one outside of boxes and cabinets
> (c) Fittings with shoulders that seat firmly against the box or  
> cabinet, such as electrical metallic tubing connectors, flexible  
> metal conduit connectors, and cable connectors, with one locknut on  
> the inside of boxes and cabinets
> (d) Listed fittings that are identified for the purpose
>
>
> 250.92 Services.
> (B) Method of Bonding at the Service. Electrical continuity at  
> service equipment, service raceways, and service conductor  
> enclosures shall be ensured by one of the following methods:
> (1) Bonding equipment to the grounded service conductor in a manner  
> provided in 250.8
> (2) Connections utilizing threaded couplings or threaded bosses on  
> enclosures where made up wrenchtight
> (3) Threadless couplings and connectors where made up tight for  
> metal raceways and metal-clad cables
> (4) Other approved devices, such as bonding-type locknuts and bushings
> Bonding jumpers meeting the other requirements of this article  
> shall be used around concentric or eccentric knockouts that are  
> punched or otherwise formed so as to impair the electrical  
> connection to ground. Standard locknuts or bushings shall not be  
> the sole means for the bonding required by this section.
>
>
>
> William Miller
>
>
> __________________________________________________________________
> William Miller
> Miller Power and Communications
> Voice :805-438-5600     Fax: 805-438-4607
> email: wrmiller at mpandc.com
> http://mpandc.com
> License No. C-10-773985
> _____________________________________________________________
> Check out our latest project at http://mpandc.com/case_studies/ 
> pv_school/pv_school.html
>
> - - - -
> To send a message: RE-wrenches at topica.com
>
> Archive of previous messages: http://lists.topica.com/lists/RE- 
> wrenches/read
>
> List rules & how to change your email address: www.mrsharkey.com/ 
> wrenches/etiquette.php
>
> Check out participant bios: www.mrsharkey.com/wrenches/
>
> Hosted by Home Power magazine
>
> Moderator: michael.welch at homepower.com
>
>


- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://lists.topica.com/lists/RE-wrenches/read

List rules & how to change your email address: www.mrsharkey.com/wrenches/etiquette.php

Check out participant bios: www.mrsharkey.com/wrenches/

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com
--^----------------------------------------------------------------
This email was sent to: michael.welch at homepower.com

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl
Or send an email to: RE-wrenches-unsubscribe at topica.com

For Topica's complete suite of email marketing solutions visit:
http://www.topica.com/?p=TEXFOOTER
--^----------------------------------------------------------------




</x-flowed>