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Bonding Bushings #87329 02/12/04 05:50 AM
Joined: Sep 2003
Posts: 60
gunther Offline OP
From searching the code, I can find only three places where bonding bushings are required. Around concentric and eccentric knock outs are two of them. The other is on the line side of the service, so I plan to put a bonding bushing on the new transformer but do I need one on the line side of the feed to the new panel?

2017 / 2014 NEC & Related Books and Study Guides
Re: Bonding Bushings #87330 02/12/04 09:35 AM
Joined: Aug 2003
Posts: 1,374
Ryan_J Offline
Re-read that code section (250.97) and you will see that it only applies to over 250 volt systems. Perhaps that will answer your question?

By the way, one other area that you would need a bond bushing would be for a metallic raceway encasing a grounding electrode conductor.

Ryan Jackson,
Salt Lake City
Re: Bonding Bushings #87331 02/12/04 11:36 AM
Joined: Sep 2003
Posts: 60
gunther Offline OP
Thanks for the tips and additional information. Now when I am reading it seems to indicate that bonding bushings are only required on the line side of theservice entrance conductors coming into service equipment, so since I am adding a transformer that is far downstream from them, I take it to mean that one is not required. That is also considering that the transformer is not establishing a new service because there isn't a meter being added.

Re: Bonding Bushings #87332 02/12/04 01:00 PM
Joined: Aug 2003
Posts: 1,374
Ryan_J Offline
Thats correct. I am assuming you have a transformer with voltages of 480/277 and 208/120, either on the primary or secondary. Whichever side the 480 is on will require bonding IF a concentric knock out is used.

Make sure you use a non-metallic raceway off your XO to the GEC, or you will have to bond it as well.

Ryan Jackson,
Salt Lake City
Re: Bonding Bushings #87333 02/20/04 12:20 AM
Joined: Feb 2001
Posts: 308
Steve T Offline
Bushings or equivalent are required around concentric/eccentric knockouts that are formed to impair the ground path.

Are all concentric/eccentric knockouts formed to impair the ground path?

Do you require or install them on 4X4's with 1/2"-3/4" concentric kos?

Ahead of the service main they are required, but many people install more than is needed and add grounding conductors which violate 250-6(a) 1999 NEC. Be careful of this.

Re: Bonding Bushings #87334 02/20/04 09:22 AM
Joined: Dec 2003
Posts: 751
earlydean Offline
Section V of article 250 starts at 250.90, where it is made clear that in any situation where the electrician suspects that grounding continuity is not too good, he will have to bond. Bonding bushings MAY be used for this purpose.
I teach my apprentices that we have levels of required bonding. The most restrictive level is " At the Service" (250.92), followed by "Over 250 Volts" (250.97), and then "Other Enclosures" (250.96).


Re: Bonding Bushings #87335 02/24/04 04:13 PM
Joined: Mar 2003
Posts: 849
Yoopersup Offline
Try 501-16 a


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