grounding bushings required?

[jusjj]

i have a general application where i have 120/208 and 277/480 volt branch panels with blank end panels. The end panels are punched to the proper size, then rigid conduit leaves the panel, travels under the slab, converts to pvc, then converts back to rigid when it penetrates the slab at its destination,; to a box, controller, or other enclosure, always having the appropriate size hole punched. Are grounding bushings required at the termination of the rigid conduits??

 

[Dennis Alwon]

Article 250.97 is what you want for over 250 volts to ground. In general I would say no bonding bushing is required.

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

 

[jusjj]

thanks, that makes sense, it's alot clearer now.