120% rule question with micro inverters

[Escapades]

On a 200 amp service with the 120% rule you can add 40 amps of solar back feed. Does this mean only 2 - 20 amp 240 volt breakers or can you use 3 - 20 amp 240 volt breakers if maximum supply from inverters can't exceed 40 amps. What if it easier to have 3 feeders that each supply only 10 inverters each? That would be a maximum of 30 x 225 watts = 6,750 watts well under the 20% but 60 amps of breakers.
Question #2 - What would be the maximum number of Enphase M215 inverters allowed on a 200 amp main service and still meet all codes?

 

[Smart $]

Could probably surmise a reply, but need more details to give you a definitive answer.

Line side or load side connection? You mentioned back feed, but you are back feeding no matter where you connect.

You can have a 200A service with a service OCPD rating that is less than 200A. If load side connection, need to clarify the equipment ratings and OCPD rating(s) on the line side.

What Code cycle?

 

[GoldDigger]

The code cycle is particularly important in terms of whether the sum of the breaker ratings or the sum of the listed maximum output ratings of the inverters or the sum of the actual inverter output powers based on the connected array input is the number you need to start from.

Tapatalk!

 

[jaggedben]

On a 200 amp service with the 120% rule ...can you use 3 - 20 amp 240 volt breakers if maximum supply from inverters can't exceed 40 amps. What if it easier to have 3 feeders that each supply only 10 inverters each?...

Under the 2014 code you're golden, because the allowable backfeed is based on the inverter output and not the breaker size. Remember though, you have to multiply the inverter output by 125%. Thus you can have 32A of inverter output regardless of how many circuits they're put on.

Under previous codes, you couldn't do this by the letter. But you might be able to convince your AHJ that you're meeting the intent of the code. I would propose something like three 15A breakers combined in a dedicated solar subpanel that's fed by a 40A breaker from the main. Obviously the backfeed to the main busbar can't be more than 40A in this situation, so a reasonable AHJ should allow it, in my opinion.

Question #2 - What would be the maximum number of Enphase M215 inverters allowed on a 200 amp main service and still meet all codes?

Strictly speaking, the answer is that with a code compliant supply side connection you can backfeed a 200A OCDP, which comes out to 200A / 1.25 / .9A per inverter = 177 inverters.