Article 250.97 using an EGC for bonding.

[SnuffyD]

On 480v equipment installation I have been pulling in a grounding wire and not using a grounding bushing at the eccentric knockout of the safety switch. The metal conduit is connected at the buss switch through a properly size knockout. The grounding conductor is attached at the buss switch ground lug and then at the safety switch using an equipment grounding terminal kit. Do I still need to use a grounding bushing at the eccentric knockout?

 

[Dennis Alwon]

Look at art. 250.97-- I say yes.

250.97 Bonding for Over 250 Volts.
For circuits of over 250 volts to ground, the electrical continuity of metal raceways and cables with metal sheaths that contain any conductor other than service conductors shall be ensured by one or more of the methods specified for services in 250.92(B), except for (B)(1).
Exception: Where oversized, concentric, or eccentric knockouts are not encountered, or where a box or enclosure with concentric or eccentric knockouts is listed to provide a reliable bonding connection, the following methods shall be permitted:
(1) Threadless couplings and connectors for cables with metal sheaths
(2) Two locknuts, on rigid metal conduit or intermediate metal conduit, one inside and one outside of boxes and cabinets
(3) Fittings with shoulders that seat firmly against the box or cabinet, such as electrical metallic tubing connectors, flexible metal conduit connectors, and cable connectors, with one locknut on the inside of boxes and cabinets
(4) Listed fittings

 

[SnuffyD]

Thanks! I was thinking the conduit was effectively bonded to the buss and the safety switch effectively bonded with the grounded conductor. But, then what happens if the conduit is damaged and seperates! Thanks again.