bonding raceways

[electricalperson]

am i required to install a bonding bushing at both ends of a metallic raceway that contains a grounding electrode conductor that starts from a main panel with no concentric knockouts. also should the bonding jumper be the same size as the GEC? example one inch EMT containing a 1/0 thhn GEC.

also another question. are bonding jumpers required in 480volt panels even if the knockouts are not concentric or ecentric? example: half inch emt carrying a few circuits feeding light switches. another example 12/2 MC leaving a panel feeding a 480v load.

im pretty sure the code requires bonding on those examples i stated above but someone at work says that its not required. i dont have a code book handy.

 

[bphgravity]

1. Yes, both ends per 250.64(E). Not necessarily. Bonding jumpers are sized per 250.28(D), GEC's are sized per 250.66.

2. Probably not. See section 250.96(A). Bonding jumpers are only required to bonded where necessary to ensure continutity of the effctive fault path, such as required in 250.98.

 

[augie47]

am i required to install a bonding bushing at both ends of a metallic raceway that contains a grounding electrode conductor that starts from a main panel with no concentric knockouts. also should the bonding jumper be the same size as the GEC? example one inch EMT containing a 1/0 thhn GEC.

also another question. are bonding jumpers required in 480volt panels even if the knockouts are not concentric or ecentric? example: half inch emt carrying a few circuits feeding light switches. another example 12/2 MC leaving a panel feeding a 480v load.

im pretty sure the code requires bonding on those examples i stated above but someone at work says that its not required. i dont have a code book handy.

If its a clean knockout (no ecentric/concentric) at the panel, my opinion would be that you could use a bonding locknut there in lieu of a bushing.
Where bushings are used, the jumper should be sized the same as the GEC.
On circuits over 250v to ground the bonding requirements are for situations where you encounter concentric/ecentric knockouts and then only if the box/cabinet is not listed to provide the grounding without such measures.

(sorry Bryan..typing as you posted)

 

[electricalperson]

thanks guys i just ordered a couplebooks from mike holt. thetheory one and 2008 grounding book but it wont ship until febuary. grounding is one of my favorite things about the trade. also the most important