NEC 120% Rule

[lvr180]

Hi guys,

This is my first post so excuses upfront.
My question is as follows: NEC states that for the breaker selection of a PV system i cannot exceed the 120% from the busbar. That means that if the pullout specification of that panel says for example 125A Max and it has a 100 A Main Breaker installed, i have 50A of breaker available right??.

Thanks in advance.

 

[ggunn]

Hi guys,

This is my first post so excuses upfront.
My question is as follows: NEC states that for the breaker selection of a PV system i cannot exceed the 120% from the busbar. That means that if the pullout specification of that panel says for example 125A Max and it has a 100 A Main Breaker installed, i have 50A of breaker available right??.

Thanks in advance.

That is correct. It must be installed at the opposite end of the panel busbar from the main breaker. You can put up to a 25A breaker anywhere on the busbar you want but anything bigger than that must be at the other end.

 

[Carultch]

Hi guys,

This is my first post so excuses upfront.
My question is as follows: NEC states that for the breaker selection of a PV system i cannot exceed the 120% from the busbar. That means that if the pullout specification of that panel says for example 125A Max and it has a 100 A Main Breaker installed, i have 50A of breaker available right??.

Thanks in advance.

If NEC2014 applies, they've rewritten the language so that instead of the PV interconnection breaker's trip rating, you get to use total inverter current * 125%. Same concept, but it avoids rounding errors being a showstopper.

 

[lvr180]

Thanks for the clarification guys.