Where to bond?

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LAYMAN JOE

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I have a 400 A Temporary service that comes in overhead, goes through a CT cabinet, into a 48" x 12"x 12" trough. It then goes into a 300 A Fused Disconnect that feeds a temp trailer.

From the trough, the Service is tapped and feeds a 125 A Main breaker panelboard that feeds an additional trailer.

Where do you bond the grounded conductor according to NEC?

There is much debate over this on the job. Any help would be much appreciated. Thanks in advance!
 
The tap for the 125 amp panel is BEFORE the 300 amp disconnect, right?

What exactly do you mean by "bond the grounded conductor"?
Bond to the GEC?
Bond to the equipment?
 
Yes, the tap is before the 300a disconnect.

Bond the grounded to the GEC.

JohnJ0906 said:
The tap for the 125 amp panel is BEFORE the 300 amp disconnect, right?

What exactly do you mean by "bond the grounded conductor"?
Bond to the GEC?
Bond to the equipment?
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A coworker says you must bond it in the trough and also at each disconnecting means. Is this a violation or just needless bonding?

Coworker says:
If you bonded just the disconnects, there are no load wires going back through the trough for an equipment ground. Therefor you must bond in the trough and at both disconnecting means. The trough conduits are PVC...

iwire said:
The bonding jumper

250.24(B)

At each service disconnecting means.
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You wouldn't bond the GEC to the grounded in the trough, but you WOULD bond the trough to the grounded conductor. 250.92

The GEC and grounded conductor would be at each disconnect, as Bob said.
 
So you agree with my coworker, right?

1-Grounded conductor to be bonded to the trough.
2-Grounded conductor bonded to 300 A disconnect.
3-Grounded conductor bonded to 125 a panelboard.

Correct?

JohnJ0906 said:
You wouldn't bond the GEC to the grounded in the trough, but you WOULD bond the trough to the grounded conductor. 250.92

The GEC and grounded conductor would be at each disconnect, as Bob said.
Click to expand...
 
What if the trough conduits were EMT and were the GEC. Wouldn't bonding the grounded conductor in the trough create a parallel path for neutral current?

JohnJ0906 said:
By bonding the GEC to grounded in the trough as well as the disconnects, you would be making a parallel path for neutral current.
Click to expand...
 
LAYMAN JOE said:
So you agree with my coworker, right?

1-Grounded conductor to be bonded to the trough.
2-Grounded conductor bonded to 300 A disconnect.
3-Grounded conductor bonded to 125 a panelboard.

Correct?
Click to expand...


That's the way I see it.
 
JohnJ0906 said:
By bonding the GEC to grounded in the trough as well as the disconnects, you would be making a parallel path for neutral current.
Click to expand...

You're not actually bonding the grounded conductor to the trough, you're bonding the trough to the grounded conductor. The trough must be bonded/grounded in some way, because it contains service conductors.

Just like a meter base (which has the grounded conductor's lugs bonded to it) and the disconnect which follows it, there often is redundant bonding which, ahead of the service disconnect, is deemed acceptable.
 
LAYMAN JOE said:
What if the trough conduits were EMT and were the GEC. Wouldn't bonding the grounded conductor in the trough create a parallel path for neutral current?
Click to expand...

Yes it would, and as Larry stated this is one time when it is permitted.
 
So what would you do if the trough were already grounded by the EMT/ GEC ?

Just bond the grounded conductor to the service disconnecting means and not to the trough?

I thank you guys for the help.
 
Last edited:
Joe,
What if the trough conduits were EMT and were the GEC. Wouldn't bonding the grounded conductor in the trough create a parallel path for neutral current?
Click to expand...
Parallel paths for grounded conductor current on the line side of the service disconect are permitted and in some cases required by the code rules.
Don
 
LAYMAN JOE said:
Thank you all and I bid you adieu
Click to expand...
You know, you never did tell us what was shocking your wife.
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