Grounding bushing

[erock1]

My question is, I have a 2000 amp mdp with 12 3" emt and 5 1 1/4 emt coming out of the top of it. I have ground bushing on all of the connectors in the mdp. On the other end of the 3" emt they go in to 6 36" x36" jbox. My project manager wants to see grounding bushing on the pipes coming in and leaving the jboxes. Same with the 1 1/4 they go in to 4 24x24 boxes. No splices in any of the boxes, voltage is 480. It seems like a lot more grounding then necessary. I understand on the service side but none of the hole are concentric or eccentric. Code references would help me out, thanks.

 

[Carultch]

My question is, I have a 2000 amp mdp with 12 3" emt and 5 1 1/4 emt coming out of the top of it. I have ground bushing on all of the connectors in the mdp. On the other end of the 3" emt they go in to 6 36" x36" jbox. My project manager wants to see grounding bushing on the pipes coming in and leaving the jboxes. Same with the 1 1/4 they go in to 4 24x24 boxes. No splices in any of the boxes, voltage is 480. It seems like a lot more grounding then necessary. I understand on the service side but none of the hole are concentric or eccentric. Code references would help me out, thanks.

If there are no service conductors or GECs in any of the conduits, then you only need a grounding bushing per code in the following scnearios:
1. The enclosure is non-metallic
2. The conduit doesn't terminate onto an enclosure on either side, and therefore needs a grounding connection
3. There are concentric or eccentric knockouts on a metal enclosure remaining, and voltage is >250V to ground

It is OK to have a "better to have and not need than need and not have" mentality about using them, because it will improve the bonding performance above the minimum required by code, and there is no adverse effect to overkill on making sure all non-current-carrying metal is bonded to the equipment grounding system. Job specs may require them, above and beyond the NEC.

 

[luckylerado]

My question is, I have a 2000 amp mdp with 12 3" emt and 5 1 1/4 emt coming out of the top of it. I have ground bushing on all of the connectors in the mdp. On the other end of the 3" emt they go in to 6 36" x36" jbox. My project manager wants to see grounding bushing on the pipes coming in and leaving the jboxes. Same with the 1 1/4 they go in to 4 24x24 boxes. No splices in any of the boxes, voltage is 480. It seems like a lot more grounding then necessary. I understand on the service side but none of the hole are concentric or eccentric. Code references would help me out, thanks.

250.97 exception 3 and 4 should apply to both ends no?

 

[erock1]

I agree with better to have and not need then to need and not have. It's just not cost effective when it's not necessary.

 

[Carultch]

250.97 exception 3 and 4 should apply to both ends no?

Good question.

If you are depending on the raceway for a ground, then yes. You should have an approved means of raceway-to-enclosure continuity on both ends.

But what if you have it bonded to enclosure #1 via standard locknuts with no ring KO's, and connected mechanically (but not bonded) to enclosure #2 which has a ring KO remaining?
(Suppose a wire EGC is used to maintain electrical continuity between enclosures, while bypassing the ring KO.)

 

[Ponchik]

If there are "NO SPLICES" in the boxes then I guess he just wants the conduits bonded together without bonding to the EGC, correct?

The conduits are already bonded together via the (assuming) metallic enclosure and wrench tights lock nuts.

I agree with some over build but sometimes it does not make sense because it will not benefit any.

 

[erock1]

If there are "NO SPLICES" in the boxes then I guess he just wants the conduits bonded together without bonding to the EGC, correct?

The conduits are already bonded together via the (assuming) metallic enclosure and wrench tights lock nuts.

I agree with some over build but sometimes it does not make sense because it will not benefit any.

To be honest I really don't know what he wants too see. To do it correctly I would have to strip out sections of the egc to bond it to the bonding bushing.