120% Rule

[jaggedben]

Is that what we're calling 705.12(D)(2)(3)(c)?

Presumably, but note there are two 100% rules. 705.12(D)(2)(3)(a) is the "sum of sources does not exceed 100%" rule, and 705.12(D)(2)(3)(c) is the "sum of branch breakers does not exceed 100%" rule.

 

[ggunn]

Presumably, but note there are two 100% rules. 705.12(D)(2)(3)(a) is the "sum of sources does not exceed 100%" rule, and 705.12(D)(2)(3)(c) is the "sum of branch breakers does not exceed 100%" rule.

I am pretty sure that they meant in either case, but we were specifically discussing 705.12(D)(2)(3)(c) with the AHJ.

 

[Howdy530]

120% rule with no main breaker

120% rule with no main breaker

Question:
A 200A main service metered electrical panel with no main disconnect (since it has only five OCPD/less than six movements of the hand) has a 50A OCPD installed on the bus bar from the new PV system. How would the 120% rule be enforced with no main breaker to de-rate?

 

[ggunn]

Question:
A 200A main service metered electrical panel with no main disconnect (since it has only five OCPD/less than six movements of the hand) has a 50A OCPD installed on the bus bar from the new PV system. How would the 120% rule be enforced with no main breaker to de-rate?

It wouldn't. In this case what you have is a supply side connection and you would be limited only to the size of the service.

BUT... some AHJ's will not allow you to make such an interconnection. San Antonio, for example, has a policy that dictates that any PV interconnection in a panel through a backfed breaker must be made in a panel with a main breaker. CPS (SATX's electric utility) has informed me that this policy came from their interpretation of the NEC.

 

[jaggedben]

Question:
A 200A main service metered electrical panel with no main disconnect (since it has only five OCPD/less than six movements of the hand) has a 50A OCPD installed on the bus bar from the new PV system. How would the 120% rule be enforced with no main breaker to de-rate?

Howdy, since you're the inspector you don't have to listen to stuff about other AHJs getting it wrong. As ggunn said, it's a supply side connection, under 705.12(A), and the 120% rule does not apply because it's not load side.