Backfed Breaker Sizing

I am looking to install a 2nd array at my home and I am working out the 120% rule for backfed breakers, which I currently exceed. The 2nd system needs to be run through a separate inverter, meter & breaker, because of 2 different incentive programs.
First system, which is currently running, has a Solaredge SE10000-US inverter with a Max Output rating of 41a and a Max OCPD of 60a. With no plans for a 2nd array, I just rather blindly used a 60a breaker.
I have a 225a rated bus and a 200a main breaker. 225a x 120% = 270a - 200a = 70a available to back feed.
My proposed 2nd system will have a SolarEdge SE5000H-US inverter with a Max Output rating of 21a and a Max OCPD of 40a.
Do I need to size the breaker for the inverter's Max OCPD rating or for the Max Output rating?
However...IF I can size the breakers for the Max output of the inverters of 41a and 21a, respectively, with 45a and 25a breakers I would be right at 70a and satisfy the 120% rule.
First system, which is currently running, has a Solaredge SE10000-US inverter with a Max Output rating of 41a and a Max OCPD of 60a. With no plans for a 2nd array, I just rather blindly used a 60a breaker.
I have a 225a rated bus and a 200a main breaker. 225a x 120% = 270a - 200a = 70a available to back feed.
My proposed 2nd system will have a SolarEdge SE5000H-US inverter with a Max Output rating of 21a and a Max OCPD of 40a.
Do I need to size the breaker for the inverter's Max OCPD rating or for the Max Output rating?
However...IF I can size the breakers for the Max output of the inverters of 41a and 21a, respectively, with 45a and 25a breakers I would be right at 70a and satisfy the 120% rule.
9.8kW Array, (34) 290w Heliene Modules, SE10000a SolarEdge Inverter. 8/12 pitch steel roof. NABCEP PVA. Minnesota.
Comments
A 25 amp tandem breaker may be possible but I don't know about a 45 amp.
You may just need to take some actual readings.
Also your breaker needs to only run at 80% of its rated capacity. Say you had a solar system that made 100 amps, you would need at least 120 amp breaker.
Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.
Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.
The rated current carrying capacity of conductors is very conservative but remember the purpose of the over current device is to protect the conductors from the source of highest potential, so the feed in breaker could be of a higher value than the inverters could produce but not exceeding that the conductors used. Say in the case the distance between the inverters warrant a larger gauge to prevent voltage drop, it would be possible to increase the gauge but the OCP should not exceed the current carrying capacity of the conductors, obviously it could be less. Hope this makes sense
Edit. I should add the value of a branch circuit OCP should never exceed the value of the main breaker.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
On the proposed 2nd system I would need a 25a (21a max output x 120% = 25a).
So 50a and 25a = 75a and is still over the max of 70a available to backfeed. Looks like I either need to size a smaller 2nd system or derate the main.
How do I determine if I can derate the main breaker?
This thread will help you with the derating main breaker questions http://forums.mikeholt.com/showthread.php?t=168448
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.
Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.