690.64(B)(2) Clarification

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JAMAN

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I was reading over this section and i'm unsure as to exactly what it means. It's a little confusing the way it's worded.

"The sum of the ampere ratings of overcurrent devices in circuits supplying power to a busbar or conductor shall not exceed 120 percent of the rating of the busbar or conductor. In systems with panelboards connected in series, the rating of the first overcurrent device directly connected to the ouput of a utility interactive inverter(s) shall be used in the calculations for all busbars and conductors."

Does it mean this:

The maximum PV circuit breaker connected to a 200A M.B. panelboard would be 160A (200A/1.2=166A).

Is this right?

Any help would be appreciated.
 
The HB states

In order to use this 120 percent factor, see 690.64(B)(7) for the required backfed overcurrent device location in relation to the utility-connected overcurrent device.
While this requirement will minimize the possibility of overloading the busbar or conductor from higher-than-rated currents, the possibility of inadvertent thermal overloading of the panelboard may still exist where plug loads are increased to the point where the load on the busbar exceeds its rating.

This language is for back fed brekers (7) requires the inverter wires to be at the opposite end of the load center from the utility feed.

(7) Inverter Output Connection. Unless the panelboard is rated not less than the sum of the ampere ratings of all overcurrent devices supplying it, a connection in a panelboard shall be positioned at the opposite (load) end from the input feeder location or main circuit location. The bus or conductor rating shall be sized for the loads connected in accordance with Article 220. A permanent warning label shall be applied to the distribution equipment with the following or equivalent marking:
 
The way i'm reading it, my example would be correct??

The 160A breaker connected to a 200A M.B. panel would be code compliant?
 
First this section only applies to systems with an utility interactive inverter. It permits the sum of the panel main breaker and the breaker for the inverter to equal 120% of the panel bus rating.
 
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So the panel would need to be rated 400A.

160A+200A=360A which = well over 120% of the 200A panel.

Does this mean the M.B. and feeders would also have to be 400A??
 
never mind, that would defeat the purpose. So a 400A panel with a 200A M.B. and feeders.

anyone else find this section confusing or is it just me?
 
JAMAN said:
never mind, that would defeat the purpose. So a 400A panel with a 200A M.B. and feeders.

anyone else find this section confusing or is it just me?
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if you had a 200 amp panel you could put max 40 amp back fed pv breaker in that 200 amp panel, the main breaker plus the pv breaker cannot exceed 120 percent of the busbar or conductor, if you were back feeding a downstream panel you would use that 40 amp PV breaker for the 120 percent calculation for other panels in series.
 
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