Curtis, I agree with Larry and will look for the code section that permits it.I looked at a job today where the installers used only the grounding bushing to connect to the chase nipples from LB's coming into the boxes. The connections were tight but am I wrong in thinking there should have been a lock nut then the grounding bushing?
Not a problem, it's not specific to locknuts but I have posted it before just couldn't remember the section off the top of my head.Good luck finding that one, I don't think the code comments on the number of lockouts required.
There would have to be at least one locknut or some type of shoulder on the back side though.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.
It was very common when installing mud boxes in poured concrete with RMC to install a metal bushing inside the box and a single locknut on the outside of the box. In those installations you still ended up with at least one locknut when connecting to the box.300.4 G, note the wording, it only prohibits bushings made of insulating material from being the sole means of connection, metal bushings that securely fastens the conduit to the box are not prohibited. I think Mike had a graphic and commentary at one time.
Have you never used metallic bushings that are not bonding bushings? They used to be somewhat common and are still made.Unless you are using threaded conduit and can get a little extra thread into your enclosure, it isn't all that often there is enough thread for a second locknut. Cinching it tight shouldn't be all that important - bonding is being achieved by tightening the set screw on the bushing more so than by tightening of "the locknut". Remember you were using a bonding bushing because improved bonding was necessary in the first place.
OP was asking about grounding bushings, but yes I have seen them on existing installations, mostly use old ones I have removed as temporary bushings while pulling so don't get rope/string burn through on a PVC TA or on the plastic bushing. Helpers never pull straight out they pull against the side wall of fittings and burn through them with pull rope.Have you never used metallic bushings that are not bonding bushings? They used to be somewhat common and are still made.
I looked at a job today where the installers used only the grounding bushing to connect to the chase nipples from LB's coming into the boxes. The connections were tight but am I wrong in thinking there should have been a lock nut then the grounding bushing?
Had to be a close nipple or other short length of conduit. How do you put a bushing (grounding or not) on a chase nipple that is also threaded into a conduit body?IMO the chase nipple requires a locknut.