When are grounding bushings required?

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wireman71

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I'm trying to get a better grasp on when grounding bushings are required.

I've read 250.92 and 250.97.

You have to bond any metallic service entrance raceways. 250.92

250 volts or more: You only have to bond raceways after the service if they terminate into concentrics or eccentrics that are not listed for bonding. 250.97.

How about flex carrying 480 3-phase stubbing up from a PVC FA to a transformer? This would be after the service. The way I'm interpreting it is that it wouldn't require a grounding bushing.

Say a grounding bushing is required on the service side, rigid conduit, no concentrics. Can you use one of these:

http://www.aifittings.com/g_3.htm
 
wireman71 said:
How about flex carrying 480 3-phase stubbing up from a PVC FA to a transformer? This would be after the service. The way I'm interpreting it is that it wouldn't require a grounding bushing.
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No bonding bushing required assuming a punched KO.
 
From the UL White Book - 2007



Metal Outlet Boxes (QCIT)
This category covers metallic flush device boxes, conduit bodies, conduit boxes, floor boxes, outlet boxes, special purpose boxes, extension rings, covers, and flush-device cover plates.


CONCENTRIC OR ECCENTRIC KNOCKOUTS
All boxes with concentric or eccentric knockouts have been investigated for bonding and are suitable for bonding without any additional bonding means around concentric (or eccentric) knockouts where used in circuits above or below 250 V, and may be marked as such.


GROUNDING
Clamps for armored cable, flexible metal conduit, metal-clad interlocking armor ground cable, metal-clad continuous smooth-sheath cable, or metal-clad continuous corrugated-sheath cable are considered suitable for grounding where installed in accordance with ANSI/NFPA 70, "National Electrical Code" (NEC).
 
Minuteman said:
Nice pics, but let's say that the meter pan is on top of the load center and has a panel hub for the nipple. Does nipple require a ground bushing boding it to the meter pan?
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Check out 250.92 (B), I believe # 2 would meet the requirement. So no bushing required inside the meter pan.
 
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stickboy1375 said:
Check out 250.92 (B), I believe # 2 would meet the requirement. So no bushing required inside the meter pan.
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That's the way I read it, but it is a local unofficial thing to require a bonding bushing on ALL nipples that have unfused conductors.
 
Minuteman said:
That's the way I read it, but it is a local unofficial thing to require a bonding bushing on ALL nipples that have unfused conductors.
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So that's a local requirement or just the "way things are done" around there? It's not an NEC requirement.
 
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