Equipment Grounding Conductor

[ath123]

I just added a new 120/208 volt standby generator to an existing system. To accommodate the addition, I added a new service entrance breaker which feeds the ATS which feeds the old service entrance equipment. The contractor was to install a new grounding electrode system connected at the new service entrance breaker, pull an equipment grounding conductor to the old service entrance equipment, remove the bonding jumper between the neutral and gound lugs at the old service entrance equipment, and disconnect the old grounding electrode conductor from the old service entrance equipment.
When the contractor went to pull the equipment grounding conductor from the ATS to the old service entrance equipment, he found the conduit had shifted and he was unable to pull in the equipment grounding conductor.
The inspector told him it was OK, but keep the old grounding electrode conductor connection at the old service entrance equipment.
Is this a code violation?

 

[alehman]

Yes it is a code violation. And it could be very dangerous! You must have an electrically continous equipment grounding conductor from the new service throughout the new and existing system. This is crucial to provide a low impedance return path for ground fault current.

A return path to the service equipment which depends only on earth means the downstream equipment is effectively ungrounded!! There is a good chance that a gound fault would not produce sufficient current to trip the service breaker. It would simply energize the equipment and quite possibly start a fire.

 

[ath123]

The new service entrance equipment and ATS are away from the building on an equipment pad with the generator. Could the building be treated as a second building and use the provisions of 250-32(b)(2), bond the neutral and ground bars back together at the old service entrance equipment and reconnect to the old grounding electrode conductor?

 

[alehman]

If there is no ground fault protection at the new service, I think what you propose would be allowed. The old switchboard would have to remain configured as "service equipment" in compliance with the those requirements. I think there were some changes recently to the NEC sections relating to grounding services for multiple buildings. You should read those sections carefully.