Hi,
We have a project where an existing building (120/208Y) is fed from a pad mount utility transformer located 100' from the building with a 4-wire service entrance. The plan is to install a concrete pad adjacent to the transformer, intercept the service conductors, and install a service disconnect, generator and ATS at the pad. The generator is not a SDS. There is an existing main beaker at the service entrance panel.
Based on 250.32, I believe that we would be required to add a separate EGC to the existing service conductors and split the neutrals and grounds at the building. The service conductors would now become an outside feeder. The problem is, we have reason to believe that the horizontal part of the service conductors are direct burial and digging up the parking lot would be a deal breaker. I see exception (2) in 250.32.B.1 allowing previously compliant installations to use the grounded conductor as the ground-fault return path, but I'm not sure that applies as I believe that refers to previously compliant outside feeders. This was previously a compliant service entrance.
From a practical standpoint, I can't see a problem with the grounded neutral carrying the ground fault return, but I want to be code-compliant.
Thoughts?
We have a project where an existing building (120/208Y) is fed from a pad mount utility transformer located 100' from the building with a 4-wire service entrance. The plan is to install a concrete pad adjacent to the transformer, intercept the service conductors, and install a service disconnect, generator and ATS at the pad. The generator is not a SDS. There is an existing main beaker at the service entrance panel.
Based on 250.32, I believe that we would be required to add a separate EGC to the existing service conductors and split the neutrals and grounds at the building. The service conductors would now become an outside feeder. The problem is, we have reason to believe that the horizontal part of the service conductors are direct burial and digging up the parking lot would be a deal breaker. I see exception (2) in 250.32.B.1 allowing previously compliant installations to use the grounded conductor as the ground-fault return path, but I'm not sure that applies as I believe that refers to previously compliant outside feeders. This was previously a compliant service entrance.
From a practical standpoint, I can't see a problem with the grounded neutral carrying the ground fault return, but I want to be code-compliant.
Thoughts?
