Service and other enclosures

[Therealcrt]

I’m reading 250.92 and 250.96 and 250.97 250.92B says that if basically reducing washers are used or oversize concentric or eccentric knockouts, they would need a bonding bushing at the service regardless of the voltage of the service. 250.97 basically says if any circuit is over 250 V to ground and the enclosure encounters a concentric or eccentric knockout it’s not encountered then a standard EMT connector or listed fitting will be sufficient enough and not require a bonding bushing at those enclosures, even though some people still put them on which is OK but not needed so does that mean that any conduit that has a circuit in it over 250 V to ground? And it enters an enclosure with concentric or eccentric knockouts or reducing washers then it would need a bonding bushing to that enclosure.? For instance if I run a piece of conduit from a panel up to a junction box and I enter that junction box to a concentric or concentric knockout and it’s got 277 V for lighting. I need to put a bonding bushing on the inside of that connector inside the enclosure and bond it to the enclosure, correct?

 

[infinity]

so does that mean that any conduit that has a circuit in it over 250 V to ground?

The requirement is based on the conductor voltage within the raceway.

For instance if I run a piece of conduit from a panel up to a junction box and I enter that junction box to a concentric or concentric knockout and it’s got 277 V for lighting. I need to put a bonding bushing on the inside of that connector inside the enclosure and bond it to the enclosure, correct?

Most 4" or 4 11/16" metal boxes are listed for bonding over 250 volts even with concentric or eccentric KO's so no bonding bushing is required.

 

[augie47]

The exception to 250.97 allows you to use boxes with concentric/eccentric knockouts which are listed for such use without additional bonding. Most, if not all, "standard" (4" sq, 4=11/16, etc) boxes are listed as such.