Article 250.97 Bonding for over 250V

[stevewilcox]

I too have some questions involving this topic. We have a 3/0 bare copper GEC in a 1" GRC connected to J-box and Substation with a Myers Hub @ J-box and Locknuts @ Substation. Both Holes were punched. Our inspector is saying that we need to include a 3/0 bond (same size as GEC) at the both ends of the conduit because of "Choke Effect". At first this seemed rediculous --bare copper in rigid??? Seemed bonded to me. But I can see that this is a legit concern. However, I'm also seeing in the code (my take) that it's not required because 250.92 (B)(2) electrcal continuity is insured by connection utilizing threaded bosses on enclosures where made up wrenchtight & 250.64 (E) ferrous metal enclosures for GEC shall be electrically continuous...

Thoughts? To appease the inspector we installed a Burndy fitting @ the substation that clamps the conductor as it exits the conduit, but not at the other end where the Meyers Hubs are employed. In this situation should we have to bond both ends? From reading the other threads it seems up in the air a little.

 

[BCSVirginia]

Article 250.97 Bonding for over 250V

I too have some questions involving this topic. We have a 3/0 bare copper GEC in a 1" GRC connected to J-box and Substation with a Myers Hub @ J-box and Locknuts @ Substation. Both Holes were punched. Our inspector is saying that we need to include a 3/0 bond (same size as GEC) at the both ends of the conduit because of "Choke Effect". At first this seemed rediculous --bare copper in rigid??? Seemed bonded to me. But I can see that this is a legit concern. However, I'm also seeing in the code (my take) that it's not required because 250.92 (B)(2) electrcal continuity is insured by connection utilizing threaded bosses on enclosures where made up wrenchtight & 250.64 (E) ferrous metal enclosures for GEC shall be electrically continuous...

Thoughts? To appease the inspector we installed a Burndy fitting @ the substation that clamps the conductor as it exits the conduit, but not at the other end where the Meyers Hubs are employed. In this situation should we have to bond both ends? From reading the other threads it seems up in the air a little.

Article 250.97 (NEC 2005) states the following: 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 in250.92(B), except for (1).Exception: Where oversized, concentric, or eccentric knockouts are not encountered, or where a box or enclosure with concentric or eccentric knockouts is listed for the purpose, the following methods shall be permitted:
(a) Threadless couplings and connectors for cables withmetal sheaths
(b) Two locknuts, on rigid metal conduit or intermediate metal conduit, one inside and one outside of boxes and cabinets
(c) 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
(d) Listed fittings that are identified for the purpose



Based on this article of the code the raceways continuity is maintained on both end by way of the rated fittings and or locknuts and therefore bonding jumpers are not required at either conduit termination.

 

[Dennis Alwon]

Article 250.97 (NEC 2005) states the following: 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 in250.92(B), except for (1).Exception: Where oversized, concentric, or eccentric knockouts are not encountered, or where a box or enclosure with concentric or eccentric knockouts is listed for the purpose, the following methods shall be permitted:
(a) Threadless couplings and connectors for cables withmetal sheaths
(b) Two locknuts, on rigid metal conduit or intermediate metal conduit, one inside and one outside of boxes and cabinets
(c) 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
(d) Listed fittings that are identified for the purpose



Based on this article of the code the raceways continuity is maintained on both end by way of the rated fittings and or locknuts and therefore bonding jumpers are not required at either conduit termination.

I agree with that