Service Ampacity / Grouped Circuit Breakers
Service Ampacity / Grouped Circuit Breakers
(OP)
I am familar with utility electric service requirements (esr) for service ampacity / short-circuit current rating when a main circuit breaker is included in the service.
How do these requirements apply to service installations with grouped meters? For example, a service with 6 - 60A circuit breakers. How do utilities determine the service ampacity (do they assume a coincident factor) and the short-circuit current?
My research shows that most utilities require that all grouped service installations contact the utility directly for short-circuit values rather than attempting to publish them for all of the possible different service scenarios.
How do these requirements apply to service installations with grouped meters? For example, a service with 6 - 60A circuit breakers. How do utilities determine the service ampacity (do they assume a coincident factor) and the short-circuit current?
My research shows that most utilities require that all grouped service installations contact the utility directly for short-circuit values rather than attempting to publish them for all of the possible different service scenarios.






RE: Service Ampacity / Grouped Circuit Breakers
The ampacity is just what ever load the utility assumes you require. In many cases, they take whatever service is requested (200 A, etc) and divide by 2. If they guess too small, they come back and put in a bigger service drop and maybe transformer.
So it depends on how many secondary services the utility wants to put on a single transformer.
RE: Service Ampacity / Grouped Circuit Breakers
The available fault current is only less than this if the Utility tells you in writing that it is less. The utility may do this if the distribution system is unable to supply the full fault current of the transformer. They may not wish to do so because of the possibility of a future upgrade to the distribution circuit.
respectfully
RE: Service Ampacity / Grouped Circuit Breakers
Regards
Marmite