Service entrance bonding bushing

[Rossboy]

Hey all, from my utility transformer to gear I have 10-3 1/2" PVC then changing over to grc as it leaves ground level into a mcc 4000a with a duct welded to the steel (grounded) floor of the mcc , I have Meyers hubs on all conduits are bonding bushings required?
Thanks

 

[augie47]

Although often universally accepted as acceptable for grounding metallic service conduits, as I understand UL White Book DWTT & KDER, hubs are acceptable for grounding only with a certified bonding locknut so it would pay to check the listing.
They also manufacturer hubs with factory bonding lugs

here is some additional input from UL:for a hub to be used to comply with 250.92 it would have to be covered by UL Product Category KDER. Below is an examples that would be covered by both UL Product Categories DWTT and KDER.

 

[texie]

I agree. If you need to comply with 250.92, yes you need the type of myers hub that is listed as KDER.

 

[JDB3]

In the picture, is the bonding lug so that it would be outside of the enclosure :?

 

[Smart $]

...

here is some additional input from UL:for a hub to be used to comply with 250.92 it would have to be covered by UL Product Category KDER. Below is an examples that would be covered by both UL Product Categories DWTT and KDER.

I agree. If you need to comply with 250.92, yes you need the type of myers hub that is listed as KDER.

Hmmm... that got me wondering about a hub (not necessarily a "myers hub") with a bonding-type locknut. The example I dug up is an Appleton HUB-350B and listed under UL File E14814 (DWTT).



If you look at the actual part no. in the UL File, it has a footnote which states:

Suitable for use with service entrance conduit.

250.92(B)(4) states: "Other listed devices, such as bonding-type locknuts, bushings, or bushings with bonding jumpers"

Is this perhaps a "gray area" in between DWTT and KDER listings???

 

[newschool]

250.92(B)(2) - "Connections utilizing threaded couplings or threaded bosses on enclosures where made up wrenchtight."

I believe the locknut is OK as long as its not going through a concentric knockout. Providing a better connection with something like a bonding lock-nut will make a better connection, however considering that your raceways are non-metallic up to the MCC the locknut should be fine.

 

[kwired]

250.80 says: "Metal enclosures and raceways for service conductors and equipment shall be connected to the grounded system conductor if the electrical system is grounded or to the grounding electrode conductor for electrical systems that are not grounded."

The metal cabinet is connected to the grounded system conductor via the system bonding jumper, but it is not the grounded system conductor. Standard locknuts are not acceptable for this connection and one must use a bonding fitting and bonding jumper to connect any metal raceway containing service conductors to the grounded system conductor.

 

[Smart $]

250.80 says: "Metal enclosures and raceways for service conductors and equipment shall be connected to the grounded system conductor if the electrical system is grounded or to the grounding electrode conductor for electrical systems that are not grounded."

The metal cabinet is connected to the grounded system conductor via the system bonding jumper, but it is not the grounded system conductor. Standard locknuts are not acceptable for this connection and one must use a bonding fitting and bonding jumper to connect any metal raceway containing service conductors to the grounded system conductor.

How do you suppose the bonding-type lock nut hub in my previous post is listed as "Suitable for use with service entrance conduit"? The raceway would not be connected to the grounded conductor directly. Instead it would be connected indirectly through the service enclosure.

 

[kwired]

How do you suppose the bonding-type lock nut hub in my previous post is listed as "Suitable for use with service entrance conduit"? The raceway would not be connected to the grounded conductor directly. Instead it would be connected indirectly through the service enclosure.

Because it is as you said "250.92(B)(4) states: "Other listed devices, such as bonding-type locknuts, bushings, or bushings with bonding jumpers""

I'll admit I did not include enough information first time around. 250.80 does mention that service raceways need bonded to the service grounded conductor, 250.92 tells us how we can do it.