PV Grid Tied Busbar Rating

[ARW Electric]

Please bear with me while I explain...

I've taken several courses on PV and I can't get a straight answer on the matter.
690.64 (B) (2) States Busbar conductor shall not exceed 120% of the rating

(B) (7) States 'Unless the panel board is rated not less than the sum of the amp ratings of all overcurrent devices supplying it, connection shall be at opposite ends of input feeders.'

Some instructors believe that is an exception to (B) (2)

Please help clarify this, Thanks.
If this is not an exception what are our options. In reality I am not looking for supposition I am looking for fact. My Local Inspectors currently are not knowledgeable to make that call.

 

[iwire]

If you had a panel bus rated as much or more than both source breakers you could install the breakers anywhere in the panel.

If the total of the source breakers is more than 100% but never over 120% the breakers must be opposite ends of the panel. This lessens the chance of actually loading any section of bus to 120%.

 

[ARW Electric]

Thanks Bob, I completely understand that but is B 7 an exception to B 2 per the 2008 code. As the 2008 Code is all NABCEP will acknowledge.

Or... is the 120% rule final. I ask as different PV Instructors are claiming it is an exception to the rule.

I am not interpreting it differently than you Bob, to me 120% is the max the busbar can have supplied to it but that is not the way it is being instructed by some or these sections of the code being interpreted.

This is a little frustrating, so thank you for your patience.

 

[SolarBri]

120%

120%

This is the maximum that any busbar can be loaded.
This includes all supply lines: generators, pv and utility feed have to be accounted for.
We use 120% as the golden rule for all our installs, and if that is not enough room to accomodate our PV breaker we will do either a supply side tap,
calculate the loads and downsize the main breaker, or upgrade the service.