1.
For supply side interconnections here it is text from 705.12(A):
The sum of the ratings of all overcurrent devices connected to power
production sources shall not exceed the rating of the service.
2.
The key here is what does it mean by “service”? // The NEC does not define the term “service”.
3.
It does not say service conductors so to me the question of the current rating of the service conductors is moot.
The rating of the service to me means the rating of the service on the utility's ledger for that service point.
So if this is a 200A residential service according to the utility then it can take 200A of PV back feed according to the code.
4.
Now on the design side I would double check the conductors to make sure the utility had properly provisioned the service as rated.
1.
Isn't the meaning of "rating of service" the same as "amperage of MDP panel main breaker OR PV breaker, whichever is greater" in this case?
So 200A PV breaker is max for a 200A service?
And if the PV breaker was larger than MDP breaker, the "rating" would be based the PV breaker (so 125A of PV and a 100A MDP on a 150A or 200A utility "service" *could* be "rated" 125A?)
2.
But it does define the service breaker or breakers and conductors and how to size them.
I mean, there is no "calculated load" for PV, PV output is the opposite of load, but you are supposed to use it the same way as load here?
230.79 Rating of Service Disconnecting Means. The service disconnecting means shall have a rating not less than the calculated load to be carried, determined in accordance with Part Ill, IV, or V of Article 220, as applicable. In no case shall the rating be lower than specified in 230.79(A),(B), (C), or (D).
(A) One-Circuit Installations. For installations to supply
only limited loads of a single branch circuit, the service
disconnecting, means shall have a rating of not less than
15 amperes.
(B) Two-Circuit Installations. For installations consisting
of not more than two 2-wire branch circuits, the service
disconnecting means shall have a rating of not less than
30 amperes.
(C) One-Family Dwellings. For a one-family dwelling,
the service disconnecting means shall have a rating of not
less than 100 amperes, 3-wire.
CD) All Others. For all other installations, the service dis-
connecting means shall have a rating of not less than
60 amperes.
3.
The rating of the service to me means the rating of the service on the utility's ledger for that service point.
So if this is a 200A residential service according to the utility then it can take 200A of PV back feed according to the code.
I see it as- the service conductor size CAN BE based on the calculated load(s), or the PV output if it is larger than loads.
I'm not sure what is based on the utility saying "200A service" other than the kVA of the transformer they provide, therefore the "maximum load".
That said, I think there's something to be said for using conductors sized for 200A feeding just a 125A MDP breaker- then you wouldn't have to touch them when adding any amount of PV breaker up to 200A.
230.23 Size and Rating.
(A) General. Conductors shall have sufficient ampacity to
carry the current for the load as calculated in accordance
with Article 220 and shall have adequate mechanical
strength
230.31 Size and Rating.
(A) General. Underground service conductors shall have
sufficient ampacity to carry the current for the load as cal-
culated in accordance with Article 220 and shall have ad-
equate mechanical strength.
4.
Aren't there some service conductors that are the customer's responsibility?