Grounding Bushing -Terminating

[jusme123]

When terminating switch gear (bottom fed), is it permissible to take the grounds inside the conduits directly to the ground bus (bypassing grounding bushing), and than run one ground wire from the ground bus to all the grounding bushings on the conduits. Code section would be appreciated! Thanks

 

[ptonsparky]

You would have to size the single EG back to the conduits for the max OCPD. Maybe a 4/0 vs 12s.

I do not believe this method is prohibited, so there will be no NEC reference to allow it.

Won't be the first time I am wrong, so just wait a bit.

Are these Service Entrance conductors or feeder and branch circuits?

 

[tkb]

I don't see a problem with it.
I have seen it many, many times.
Seems like it would be the same as if they were terminated through a KO.

 

[LarryFine]

I don't see a problem with it.
I have seen it many, many times.

Same here, on both counts.

Seems like it would be the same as if they were terminated through a KO.

If not better.

 

[marti smith]

250.92(b)4

 

[tkb]

250.92(b)4

I don't see where the OP said this was a service.
It could be a feeder.

Whether it is a service or feeder the conduits are bonded with either method.

 

[RUWired]

Whether it is a service or feeder the conduits are bonded with either method.

The size of the bonding jumper is what would matter. With service conductors the jumper is sized per 250.66 and feeder bonding jumpers would be sized per 250.122.

Rick

 

[jusme123]

It is the service for an 1800 amp switch gear, thanks for all the responses!!

 

[augie47]

If it's a service, you may create a problem. A single bonding jumper would need to be sized to the sum of the area of the service conductors {250.102(C)} and you could end up with a conductor so large as to require upsized of lugs, etc.
With individual bonds they only need to be sized to the conductor in the one conduit they bond.

On feeders the jumper would be sized by the largest OCP device so there is no normally a problem using just one jumper.

 

[jusme123]

If it's a service, you may create a problem. A single bonding jumper would need to be sized to the sum of the area of the service conductors {250.102(C)} and you could end up with a conductor so large as to require upsized of lugs, etc.
With individual bonds they only need to be sized to the conductor in the one conduit they bond.

On feeders the jumper would be sized by the largest OCP device so there is no normally a problem using just one jumper.

Augie, my stance is that the ground in the conduit is to be connected to the grounding bushing and than continue to the ground bus

 

[Cow]

Augie, my stance is that the ground in the conduit is to be connected to the grounding bushing and than continue to the ground bus

Why do you have ground wires in service conduits?

 

[tkb]

If it's a service, you may create a problem. A single bonding jumper would need to be sized to the sum of the area of the service conductors {250.102(C)} and you could end up with a conductor so large as to require upsized of lugs, etc.
With individual bonds they only need to be sized to the conductor in the one conduit they bond.

On feeders the jumper would be sized by the largest OCP device so there is no normally a problem using just one jumper.

So that would be 3/0 for a service and 250 for a feeder.

Augie, my stance is that the ground in the conduit is to be connected to the grounding bushing and than continue to the ground bus

Based on...

 

[augie47]

So that would be 3/0 for a service and 250 for a feeder.

...

As I read it, if he had an 1800 amp service composed of (5) conduits with 500 kcmil, he could run a 3/0 to each conduit, or if he chose to run only 1 jumper for all it would nedd to be 350 kcmil (12.5% of total).


For an 1800 amp feeder it would be a 250 kmil to each or to all.

 

[tkb]

As I read it, if he had an 1800 amp service composed of (5) conduits with 500 kcmil, he could run a 3/0 to each conduit, or if he chose to run only 1 jumper for all it would nedd to be 350 kcmil (12.5% of total).


For an 1800 amp feeder it would be a 250 kmil to each or to all.

Opps...I didn't read the note under the table.