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#84501 - 04/04/03 05:43 PM nipple installation requirements  
gserve  Offline
Joined: Mar 2003
Posts: 92
When installing a rigid conduit nipple between the back of a meter socket to the back of a panel is it required to have 2 locknut's on each end(in and out)and is only 1 bonding bushing required on either end of the nipple?

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#84502 - 04/04/03 09:36 PM Re: nipple installation requirements  
resqcapt19  Offline
Joined: Nov 2000
Posts: 2,148
While I want to say that two locknuts are required on at each end of the nipple, I can't find a code rule that requires this. There are some rules in Chapter 5 that require double locknuts, but not in the general use chapters. Our power company requires grounding bushings at both ends, but the code rule in 250.92 does not really say that. This is one that I would run by the AHJ before making the installation.


#84503 - 04/04/03 10:30 PM Re: nipple installation requirements  
russ m  Offline
Joined: Feb 2003
Posts: 169
I require bonding bushings on both sides of the nipple.
With the neutral lugs of the meter fitting (pan) bonded to case ground, and the neutral bonded in the main panel, there is current flow on the nipple.


[This message has been edited by russ m (edited 04-04-2003).]

#84504 - 04/04/03 10:44 PM Re: nipple installation requirements  
Gwz  Offline
Joined: Apr 2002
Posts: 197
I agree with Don that the words ' double locknuts ' are not used.

Would not 344.2 " - - - when installed with its integral or associated couplings and appropriate fittings. - - -."


300.10 " - - - shall be connected to all boxes, fitting, and cabinets so as to provide effective electrical continuity. - - - raceways - - - shall be mechanically secured to boxes, - - -."

in effect mandate double locknuts for the appropriate installation?

The additional Bonding Bushings etc. of 250.92(B) would be in addition to the double locknuts.

#84505 - 04/05/03 12:31 PM Re: nipple installation requirements  
ElectricAL  Offline
Joined: Oct 2001
Posts: 597
Minneapolis, MN USA

I like the way you got at that. I agree. Locknuts inside and outside of an enclosure wall.

About the bonding of the nipple at both ends. . .The raceway isn't a conductor. I agree that, when the raceway is conductive, it will be a parallel path for the unbalance current that is not returning towards the transformer through the GEC. But the neutral is chosen and sized for its current carrying properties, not the raceway except, if it is conductive, that it provide a fault current path of sufficiently low impedance as to clear the poco's OCP at the xformer.

While bonding the nipple at both ends provides even better performance, bonding it only at one end is all that is required on the poco side of the service disco & OCP.

Our poco doesn't make specific bonding requirements, rather, it leaves that to the NEC and the AHJ.

Al Hildenbrand

#84506 - 04/05/03 02:08 PM Re: nipple installation requirements  
sparky66wv  Offline
Joined: Nov 2000
Posts: 2,236
West Virginia
After being learned here on ECN, I have opted to forgo the whole Galv. Rigid Nipple deal and use only PVC.

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#84507 - 04/05/03 03:29 PM Re: nipple installation requirements  
gserve  Offline
Joined: Mar 2003
Posts: 92
Yeah, I would use PVC too but this is a commercial garage and PVC is not allowed.

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