Bonding bushings with locknut

[ramsy]

Since a bonding bushing stops like a threaded bottle cap, inside the box, the outside connector rubber is sloppy, not tightly sealed to the outside of the box.

Therefore, a tapered locknut is used as a spacer to close the thread gap, which tightens the seal against the box.

The question is which side of the box to put the old locknut / spacer.

Electrical guy says bonding bushing should not have the old locknut behind it, since it's not intended or listed for use with another locknut behind it.

In all cases the bonding bushing is inside the box, as it should be. However, when the added locknut is outside the box, the rubber seals better, since the locknut prevents it from folding over backwards during tightening.

Both foreman also agree inspectors could red tag the locknut for being on the outside of the box, regarless of its critical use as a spacer and seal protector.

Mechanical guy points out, when combined together inside the box, the first locknut digs into the box paint and bonds better, since the smooth-backed, bonding bushing cannot. No debate there either.

Are bonding bushings listed for use with locknuts?

Are locknuts listed for use outside of a box?

 

[mdshunk]

I always put it on the inside when using sealing type connectors on the outside. Never occured to me to do otherwise.

 

[infinity]

What type of raceway are you using?

 

[ramsy]

Thanks for the replies. The raceway is EMT, except for rigid Myers hubs used on the large metal pull boxes (no bonding bushing).

Don't know why Myers were ordered, its redundant, but the sealing-EMT connector is being threaded behind the Myers hub. That is where I first saw the EMT-connector locknuts on the outside of the box, acting as both a needed spacer, and protecting the seal from folding backwards or popping completely out of place.

Even though EGC's are specified with all conduit, several smaller plastic pull / combiner boxes need bonding bushings to bond EMT to the grounding bus, since the plastic box can't do it.

The only case where sealing-EMT connectors are directly connected to metal boxes without Myers hubs is at the disconnects.