Concrete Pullbox Ground Bushing RGS conduit

[W@ttson]

Hello All here is the issue:

We have several precast concrete sidewalk pull boxes with cast iron covers roughly 24”x 36”x18”. Conduits that enter the pull boxes are RGS. The conduits currently have insulated throat ground bushings with a bare copper conductor bonding all of the conduits together. The voltage is 208V/120V. Currently, no splices in the pull box. There are three different branch circuits in the various conduits that enter the pull boxes. Each conduit has at least one dedicated ground conductor. Cover not bonded to bare copper jumper mentioned earlier.

Issue: All of the conduit ends inside the pull box are corroded and the ground bushings have more or less rusted off of the conduit.

Scenario 1:
As is, are the ground bushings required? No splices are performed in the pull box, not using the raceway as a EGC since dedicated ground conductors are in each conduit, and I don’t believe the non-concentric knockout stipulation applies.

Code sections reviewed:
250.148, 250.96(A), 250.97 (for reference if it was over 250V), 250.92(B) (for reference if it were a service or over 250V),

At the minimum I feel that this installation is in violation of 314.30(D) due to lack of cover bonding. Though I don’t know because 314.30(D) points to 250.96(A) which says “…and other non-current-carrying parts that are to serve as equipment grounding conductors…”.

Scenario 2:
How does the all of the above change if a splice is made inside the pull box of one of the circuits due to replacing a section of that circuit further down the line?

 

[Sierrasparky]

Hello All here is the issue:

We have several precast concrete sidewalk pull boxes with cast iron covers roughly 24”x 36”x18”. Conduits that enter the pull boxes are RGS. The conduits currently have insulated throat ground bushings with a bare copper conductor bonding all of the conduits together. The voltage is 208V/120V. Currently, no splices in the pull box. There are three different branch circuits in the various conduits that enter the pull boxes. Each conduit has at least one dedicated ground conductor. Cover not bonded to bare copper jumper mentioned earlier.

Issue: All of the conduit ends inside the pull box are corroded and the ground bushings have more or less rusted off of the conduit.

Scenario 1:
As is, are the ground bushings required? No splices are performed in the pull box, not using the raceway as a EGC since dedicated ground conductors are in each conduit, and I don’t believe the non-concentric knockout stipulation applies.

Code sections reviewed:
250.148, 250.96(A), 250.97 (for reference if it was over 250V), 250.92(B) (for reference if it were a service or over 250V),

At the minimum I feel that this installation is in violation of 314.30(D) due to lack of cover bonding. Though I don’t know because 314.30(D) points to 250.96(A) which says “…and other non-current-carrying parts that are to serve as equipment grounding conductors…”.

Scenario 2:
How does the all of the above change if a splice is made inside the pull box of one of the circuits due to replacing a section of that circuit further down the line?

I don't believe cover bonding was a requirement in the past. So that would depend on the year built.

 

[W@ttson]

I don't believe cover bonding was a requirement in the past. So that would depend on the year built.

I didn't think of that. I supposed that's a good point about the cover. What are your thoughts on the ground bushing requirement or on the splicing vs no splicing.

 

[Cow]

I didn't think of that. I supposed that's a good point about the cover. What are your thoughts on the ground bushing requirement or on the splicing vs no splicing.

Let me ask you this way. If the ground bushings were not there, would you have isolated unbonded sections of rigid with energized conductors installed in them?

 

[W@ttson]

Let me ask you this way. If the ground bushings were not there, would you have isolated unbonded sections of rigid with energized conductors installed in them?

Hmmg, I guess this is one of those, not being able to see the trees through the forest. I suppose, 250.4 and 250.98 pretty clearly indicate that all metal raceway needs to maintain electrical continuity. I guess I got so wrapped up with 250.148 and boxes and also the fact that a supplementary code that I need to follow for my specific application requires ground bushings at every entry into a box on every conduit, so I never put too much thought to them.

Thanks guys!

 

[don_resqcapt19]

Hmmg, I guess this is one of those, not being able to see the trees through the forest. I suppose, 250.4 and 250.98 pretty clearly indicate that all metal raceway needs to maintain electrical continuity. I guess I got so wrapped up with 250.148 and boxes and also the fact that a supplementary code that I need to follow for my specific application requires ground bushings at every entry into a box on every conduit, so I never put too much thought to them.

Thanks guys!

I was going to say that if the metallic conduit is bonded at the other end, you would not need a bonding jumper at the concrete enclosure but I think you can read 300.10 as requiring a bonding jumper in the concrete enclosure.