In regard to threaded grounding bushings (with grounding lug on it), where are these to be installed? I was checking 250.97 and 300.4(G) in the code. If possible, could you refer me to the code sections, where we must install such bushings, as compared to normal bushings? Just trying to have code references, so we don't install ground bushings where they are not needed. Thanks - Good day SJT
The SINGLE most common use for such grounding bushings is at the terminus of an EMT, GRC, IMC, Flex shielded run on a GEC -- wherever its headed.
Sometimes I've installed them as a grounding lug even with a naked bare GEC system bonding conductor.
Other than that, they've got little purpose.
They are never used to replace lazy-lugs/ lay-in lugs.
And they are typically UL listed for conductor size -- maxxed at 3/0 -- the largest GEC from the table.
That's one hint from the manufacturer/ UL as to their purpose -- they're choke eliminators -- and the inspector will be looking for them on all GEC bonding runs that are wrapped in steel pipe/ steel flex.
They are NOT required if the same run is wrapped in PVC.
As for GEC Systems, the NEC Handbook has sweet illustrations. Exhibit 250.32 [ BTW, the bushing is normally attached physically to the raceway -- but it doesn't absolutely have to -- see the diagram.