This is something I have never seen.
Can anyone tell me if there are any circumstances where Article 250.(B)(2) supercedes the requirement of Article 250.24(A) and 250.24(C) when none of the the conditions of Article 250.21 are met and/or where none of the exceptions of Article 250.22 apply?
I recently visited a site that has two 800A services, 277/480v, 3?, two 4" PVC conduits per service with three 500 MCM conductors only, in each one. Using a clamp on DGM, the impedance of the Utility Company grounding/grounding electrode conductor was 81.5 ohms. I spoke with the AHJ and they do not have jurisdiction at this location; it is all being handled by the owner and GC.
The main bonding jumper consists of a 3/0 bare cu conductor, one-hole mechanical lugs, and a split bolt, none of which appeared to be torqued correctly. The bond begins on the left rear of "Service 2" enclosure, loops to the right rear of of "Service 1" enclosure, then a short jumper from the left rear of "Service 1" enclosure to the Ultility Company "ground" from the three transformers mounted above the services. The impedance of this last 3/0 jumper was 18.3 ohms proving the NEC required main bonding jumper
My opinion is this is a dangerous situation where touch potentials are quite likely; there has already been one instance where lightng took out most of the process computers and the utility company lost one of its' transformers.
Many thanks to Mike for creating this network.
Regards,
Can anyone tell me if there are any circumstances where Article 250.(B)(2) supercedes the requirement of Article 250.24(A) and 250.24(C) when none of the the conditions of Article 250.21 are met and/or where none of the exceptions of Article 250.22 apply?
I recently visited a site that has two 800A services, 277/480v, 3?, two 4" PVC conduits per service with three 500 MCM conductors only, in each one. Using a clamp on DGM, the impedance of the Utility Company grounding/grounding electrode conductor was 81.5 ohms. I spoke with the AHJ and they do not have jurisdiction at this location; it is all being handled by the owner and GC.
The main bonding jumper consists of a 3/0 bare cu conductor, one-hole mechanical lugs, and a split bolt, none of which appeared to be torqued correctly. The bond begins on the left rear of "Service 2" enclosure, loops to the right rear of of "Service 1" enclosure, then a short jumper from the left rear of "Service 1" enclosure to the Ultility Company "ground" from the three transformers mounted above the services. The impedance of this last 3/0 jumper was 18.3 ohms proving the NEC required main bonding jumper
My opinion is this is a dangerous situation where touch potentials are quite likely; there has already been one instance where lightng took out most of the process computers and the utility company lost one of its' transformers.
Many thanks to Mike for creating this network.
Regards,