When bonding not required

[Fly4fun]

I'll try and keep this simple
(4) 4" rigid conduit entering a pull box on one side and (4) 4" leaving from the opposite side.

Conductor/amps not necessary for this question.

All 4" knock outs made via knock out punch, not pre-made.

Hence it's my understanding that ground bushings are only required at the ends, not at each pull box if no
splices occur in the pull box.
What I've see in the field is (plastic bushings only) on the pull box entry and exit.
With ground bushings at either end of the run.


Now let's say the engineer has required ground bushings on every conduit at every pull box.
The conduits in question have an appropriate ground wire run inside along with phases and neutral.

What I've seen in the field more than once is a much smaller ground wire, than is contained in the conduit
run, bonding all the ground bushing together and finally to a lug on the metal box. No connection with the feeder
ground wire.

Where the conduit is grounded without the bonding jumper, is this procedure legal?

Thanks, hope it's simple enough.

 

[ActionDave]

If everything from start to finish is metal I don't see the need for a bond bushing or a wire EGC anywhere.

 

[augie47]

Looking at 250.92(A), if these were service conduits you could not depend on "standard locknuts or bushings" but, since you have an EGC, they are likely feeder circuits.
Looking at 250.97, if the circuits were over 250 volts to ground you would need to employee some
bonding means around concentric or eccentric knockouts, but you have no such knockouts.,
If you were installing them to meet engineering specs, I doubt the undersized jumper at your j box would be acceptable.

 

[tom baker]

Both Soares and IEEE Green Book suggest bonding one end of any raceway with >250 IE bonding bushings, locknuts. But code does not requires this if clean KO,s (different rules for service conductors...)

 

[texie]

Looking at 250.92(A), if these were service conduits you could not depend on "standard locknuts or bushings" but, since you have an EGC, they are likely feeder circuits.
Looking at 250.97, if the circuits were over 250 volts to ground you would need to employee some
bonding means around concentric or eccentric knockouts, but you have no such knockouts.,
If you were installing them to meet engineering specs, I doubt the undersized jumper at your j box would be acceptable.

I would agree. If this is a feeder or branch circuit no bonding bushings would be required. But as you mentioned, if you use them because the job specs call for them, the bonding jumper would have to comply with Table 250.122.