Bonding Bushings

[Big Guns]

If you use a bonding bushing do you need a lock nut

 

[infinity]

Do you mean a bonding locknut? If the KO is the same size as the conduit then a bushing might not be needed and a bonding locknut can be used instead.

 

[augie47]

I can not cite a Code reference. Perhaps I am at fault for allowing it, but I have encountered situations where, for one reason or another (usually poor planning ), a locknut could not be installed and the E/C bonded the conduit using a bond bushing.
Other than poor workmanship, I don't see much difference in those situations and a metallic conduit stubbed up in on open bottom switchboard and bonded by a bushing/jumper.

 

[tkb]

No, I think he means using a locknut on the outside of the enclosure and just a bonding bushing on the inside without a locknut.

I have seen many old installations with a locknut and steel bushing without the locknut on the inside.

I haven't looked it up, but I think double locknuts are only required if the voltage is over 250v to ground.

I assume we are discussing RGS. I am not sure if you can eliminate the locknut on EMT in lieu of a bonding bushing.

I know there may not be enough threads on an EMT connector to allow a locknut and a bonding bushing to be affectively installed so the set screws can be engaged.

 

[iwire]

300.4(G) Insulated Fittings. Where raceways contain 4 AWG
or larger insulated circuit conductors and these conductors
enter a cabinet, box, enclosure, or raceway, the conductors
shall be protected by a substantial fitting providing a
smoothly rounded insulating surface, unless the conductors
are separated from the fitting or raceway by substantial
insulating material that is securely fastened in place.

Exception: Where threaded hubs or bosses that are an integral
part of a cabinet, box, enclosure, or raceway provide
a smoothly rounded or flared entry for conductors.

Conduit bushings constructed wholly of insulating material
shall not be used to secure a fitting or raceway. The
insulating fitting or insulating material shall have a temperature
rating not less than the insulation temperature rating
of the installed conductors.

In my opinion that tells us a typical bonding bushing could be used to secure a raceway or fitting.

 

[kwired]

In my opinion that tells us a typical bonding bushing could be used to secure a raceway or fitting.

I agree.
Also if you are putting a grounding bushing on a fitting instead of threaded conduit there are never enough threads for both the grounding bushing and a locknut.

 

[Cow]

I believe our inspector makes it a point to call us on it if we don't use a locknut under the ground bushing. It's been a long time since we've been cited so I don't know the reference he gave us.

 

[Pierre C Belarge]

In my opinion that tells us a typical bonding bushing could be used to secure a raceway or fitting.

I agree, only adding the bonding bushing should most likely be metallic if used to secure the raceway to the enclosure.

 

[kwired]

I agree, only adding the bonding bushing should most likely be metallic if used to secure the raceway to the enclosure.

How good of a job of bonding do you suppose it will do if it is not metallic?

 

[stew]

Inspectors in my area will all cite you if you dont use the locknut plus the bushing. If I cant get the 2 parts to thread I use a gounding locknut and then a separate bushing.Got cited once and not sure what code section was used.

 

[infinity]

On RMC the NEC allows a metal bushing and one locknut. Boxes in poured decks have been done this way for almost a century.

 

[stew]

If you look at many of the exhibits in bonding area of 250 you will see the single locknut and use of a grounding bushing without the second internal locknut all over the place! Didnt see that until just now. Seems when I got the citiation way back when I may have not fought the dang thing and just assumed the inspector was correct. If I ever get it again I will know where to show him the error of his mind.