rlm

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rlmalone said:
I'm using a metal insulated grounding bushing on EMT connectors. Do I need a locknut under the bushing?
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How you would get a grounding bushing to reach the wall of the enclosure when using EMT connectors? Even if you were using RMC with a locknut on the outside and the grounding bushing on the inside as a locknut I don't believe the grounding bushing listing would allow it to serve as a locknut.
That said, there is a product that I just received a sample of from Bridgeport that is a combination locknut/grounding bushing and would do this in a compliant manner. But it is only available in 3/4 and 1 inch. See here: https://www.bptfittings.com/store/catalogsearch/result/?q=Grounding+lock+nut
Is this by chance a nonmetallic enclosure and the wall is to thick for both a lock nut and grounding bushing? There is now a product for that too-extra long thread EMT connectors. I think this is also Bridgeport as I recall.
 
Yes, Locknut is required!

Yes, Locknut is required!

rlmalone said:
I'm using a metal insulated grounding bushing on EMT connectors. Do I need a locknut under the bushing?
Click to expand...
The EMT Connector's UL Listing is a combination of the connector and all of the components with which it comes with...Set screw, compression collar and yes, Locknut.
 
texie said:
How you would get a grounding bushing to reach the wall of the enclosure when using EMT connectors? Even if you were using RMC with a locknut on the outside and the grounding bushing on the inside as a locknut I don't believe the grounding bushing listing would allow it to serve as a locknut.
That said, there is a product that I just received a sample of from Bridgeport that is a combination locknut/grounding bushing and would do this in a compliant manner. But it is only available in 3/4 and 1 inch. See here: https://www.bptfittings.com/store/catalogsearch/result/?q=Grounding+lock+nut
Is this by chance a nonmetallic enclosure and the wall is to thick for both a lock nut and grounding bushing? There is now a product for that too-extra long thread EMT connectors. I think this is also Bridgeport as I recall.
Click to expand...

One locknut one the outside and a metal bushing on the inside was how RMC was installed for many decades. Really no different than an EMT connector with a single locknut. Regarding this it's covered in 300.4(G):

(G) Insulated Fittings. Where raceways contain 4 AWG
or larger insulated circuit conductors, and these conductors
enter a cabinet, a box, an enclosure, or a raceway, the con-
ductors shall be protected by an identified fitting providing
a smoothly rounded insulating surface, unless the conduc-
tors are separated from the fitting or raceway by identified
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 pro-
vide a smoothly rounded or flared entry for conductors.
Conduit bushings constructed wholly of insulating ma-
terial shall not be used to secure a fitting or raceway. The
insulating fitting or insulating material shall have a tem-
perature rating not less than the insulation temperature rat-
ing of the installed conductors.
Click to expand...
 
A lock-nut is required between the enclosure and the grounding bushing.
The lock-nut secures the conduit to the enclosure and the bushing makes contact (the bond) with the conduit.
 
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