What determines the service size? Breaker or conductors?

[ryangittens]

NEC 2017, 2014 references service size for the max supply side connection OCPD.

If the wires support a larger amperage than the main breaker would it be appropriate to use the conductors as the service size so we can use a bigger OCPD for the solar than the main?

 

[wwhitney]

While 2017 NEC 705.12(A) refers to the "rating of the service," in the 2020 NEC, 705.11(A) clarifies this to "ampacity of the service conductors."

So since both physics and the 2020 NEC wording indicate that "rating of the service" means the ampacity of the conductors, not the service OCPD size, then I'd say that would be the proper interpretation for the 2017 NEC.

Cheers, Wayne

 

[pv_n00b]

I would go by not only the size of the service entrance conductors but also the service rating that the utility has provisioned the site for. I've been bitten before when sizing a system based on the customer service equipment size only to find out the utility has installed a smaller service transformer than the service conductors might imply. Upsizing the utility transformer was not an option so the system size had to be reduced.

 

[ryangittens]

While 2017 NEC 705.12(A) refers to the "rating of the service," in the 2020 NEC, 705.11(A) clarifies this to "ampacity of the service conductors."

So since both physics and the 2020 NEC wording indicate that "rating of the service" means the ampacity of the conductors, not the service OCPD size, then I'd say that would be the proper interpretation for the 2017 NEC.

Cheers, Wayne

Thank you

 

[ryangittens]

I would go by not only the size of the service entrance conductors but also the service rating that the utility has provisioned the site for. I've been bitten before when sizing a system based on the customer service equipment size only to find out the utility has installed a smaller service transformer than the service conductors might imply. Upsizing the utility transformer was not an option so the system size had to be reduced.

Thank you