Dual Service

[sharan]

NFPA 70 700.12(D) states the two services are “sufficiently remote electrically and physically” from each other to use one as a primary and one as a secondary power source for an Emergency system. What is remote and physical separate means? Is there a distance of certain feet?

 

[GoldDigger]

NFPA 70 700.12(D) states the two services are “sufficiently remote electrically and physically” from each other to use one as a primary and one as a secondary power source for an Emergency system. What is remote and physical separate means? Is there a distance of certain feet?

Like many code sections, there is no precise definition.

Electrically separate would mean not connected to the same transformer, or even to the same closest upstream OCPD that might cut both off at the same time.
Ideally, it would mean originating from separate substations. If you could get service from two power companies it would be even better.

Physically separate would mean that something that physically interrupts one supply is not likely to also interrupt the other.

Putting both on the same pole or in the same duct bank would not be physically separate.
At some point they have to come together at the transfer switch, but both going into the transfer switch through the same raceway would probably be rejected too.

Bottom line it will be an AHJ call, so try to get it pre-approved by electrical and inspectors before betting the project on it!