# Bonding bushings, 4000A circuits, extremely large EGC's



## Black Dog (Oct 16, 2011)

Carultch said:


> What is the practice for connecting to bonding bushings, when the NEC requires extremely large EGC's?
> 
> Given a 4000A circuit, parallelled in numerous sets of conduit, each one with a 500kcmil EGC, how does the NEC require you to connect to bonding bushings that don't have lugs this large?
> 
> ...


That is what I would do, you're simply bonding the pipe to the enclosure, so you do not need 500's for that.


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## Pete m. (Nov 19, 2011)

250.102(D) has no "wiggle room". You are stuck using 500kcmil based on the 4000 amp OCPD.

Surely there is a manufacturer that carries the correct equipment.

Pete


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## Pete m. (Nov 19, 2011)

My above post assumed an open bottom switch board.

If these are raceways such as EMT that are connected to the gear through KO's that you have punched you may not need bonding bushings at all.

Pete


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## Black Dog (Oct 16, 2011)

Pete m. said:


> 250.102(D) has no "wiggle room". You are stuck using 500kcmil based on the 4000 amp OCPD.
> 
> Surely there is a manufacturer that carries the correct equipment.
> 
> Pete


I liked my answer better...:whistling2::laughing:


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## Mshea (Jan 17, 2011)

a 4000 amp service needs a 500 kcmil bonding wire if it was served by a single raceway but if you use 10 raceways I would run a number 3 to each bonding bushing and not 8- 500 kcm bonding jumpers.

Each set of 500 kcm parallel feeds would have around 400 amps and the fault would divide across all 10 raceways. the Canadian tables show #3 as the bonding jumper size for 400 amp conductors and the code allow this method of division of currents. So we take the ampacity of the largest ungrounded conductor in each set and match the bonding jumpers to that raceway. For comparison 4 raceways with 1000 amp sets would need 2/0 bonding jumpers from the grounding buss to the bonding bushing on each raceway.


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## ponyboy (Nov 18, 2012)

Why the bonding bushings at all? I'm assuming you punched your own holes which would not require the bushings unless it was impaired in some way. If it's not speced I wouldn't do it all


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## ponyboy (Nov 18, 2012)

Wait, is this a service or a branch circuit?


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## Pete m. (Nov 19, 2011)

ponyboy said:


> Wait, is this a service or a branch circuit?


If it were service conductors I highly doubt you would have EGC's in the raceways.

Pete


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## ponyboy (Nov 18, 2012)

Pete m. said:


> If it were service conductors I highly doubt you would have EGC's in the raceways. Pete


That's what I thought too but he said service.


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## Cow (Jan 16, 2008)

How does this metal raceway connect to the gear?


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## Carultch (May 14, 2013)

Cow said:


> How does this metal raceway connect to the gear?


I'm not entirely sure. It isn't me installing it.

This is for a line side solar interconnection, on an existing large commercial building.

It connects from a new outdoor switchgear, to an existing indoor switchgear. The indoor part of it is EMT, and the outdoor part of it is an overhead run of RMC spanning a sidewalk.

Is it only the "concentric knockouts remaining" rule, and non-metal enclosures, that would require bonding bushings?



ponyboy said:


> Wait, is this a service or a branch circuit?


Is it a "service"? I'm not entirely sure. The distinction between a "service" and an ordinary feeder isn't intuitive to me, so I treat just about everything I do as a feeder. I don't understand what it is physically about a "service" that allows for less ampacity in wires, and other subtle differences in NEC requirements. The last time I checked, the laws of physics are the same in all wires.


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## manchestersparky (Mar 25, 2007)

O-z /Gedney makes bonding bushings that you can get a 500 kcmil lug on them. The conduit size with these large lugs starts a 2 1/2 "

I see contractors using them all the time.

http://www.emersonindustrial.com/en...ed-Ground-Bush-Threaded-Rigid-Conduit-IMC.pdf


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