I am getting ready to install an addtional 2 KW grid tie system and want to avoid a line side tap. The local area really doesnt have any master electricans with solar experience so I need to work with one and point him in the right direction . The local inspector has no electrical background and basically has told me that a master has to sign off on the install. The area uses NEC 2011
Here is what I have
200 Amp breaker panel, there is no bus rating so I will assume it is 200 AMP bus
One 2 KW grid inverter - 8.35 max amps hooked to a 2 pole 15 amp breaker
One 1 KW grid inverter - 8.35 max amps hooked to a 1 pole 15 amp breaker
New 2 KW grid tie inverter - 8.35 max amps hooked to 2 pole 15 amp breaker.
The breaker amperage ratings are all the manufacturers recomended sizing and down sizing to 10 Amp breakers would exceed the 80% continuous rating of the breaker
120% backfeed is 40 AMPs maximum based on breaker ratings, If I look at the potential load per bus leg , I have an unbalanced backfeed with 30 Amps on one leg and 45 amps on the other. I assume this will not fly?
I do see references to 705.12(D)(2) Exception for battery sourced multimode inverters, that is real tempting as then all I have to do is add up the inverter ratings and multiply by 1.25. This yields 31.3 and 20.8 amps. Looks like this works but since I have battery less units I expect this wont fly ? Arguably either unit is limited on its output by internal circuitry but the code is the code
Options
All three arrays have different exposures, I wouldnt mind buying the new inverter with dual MPPT but they seem to have fallen out of favor.
Install a 110 to 220 volt step up transformer on the 1 KW unit and switch to a smaller 2 pole breaker? This balances the load and gets me below 40 amps if I install a 10 amp 2 pole breaker. At that point I would probably do a line size tap due to the cost and loss of the transformer.
Install a subpanel for PV only, have it feed a 40 amp breaker in the main panel.? This wouldnt be so bad but I am not sure the code allows this?
So anyone have any suggestions or thoughts besides shutting down the 1 KW system?
Here is what I have
200 Amp breaker panel, there is no bus rating so I will assume it is 200 AMP bus
One 2 KW grid inverter - 8.35 max amps hooked to a 2 pole 15 amp breaker
One 1 KW grid inverter - 8.35 max amps hooked to a 1 pole 15 amp breaker
New 2 KW grid tie inverter - 8.35 max amps hooked to 2 pole 15 amp breaker.
The breaker amperage ratings are all the manufacturers recomended sizing and down sizing to 10 Amp breakers would exceed the 80% continuous rating of the breaker
120% backfeed is 40 AMPs maximum based on breaker ratings, If I look at the potential load per bus leg , I have an unbalanced backfeed with 30 Amps on one leg and 45 amps on the other. I assume this will not fly?
I do see references to 705.12(D)(2) Exception for battery sourced multimode inverters, that is real tempting as then all I have to do is add up the inverter ratings and multiply by 1.25. This yields 31.3 and 20.8 amps. Looks like this works but since I have battery less units I expect this wont fly ? Arguably either unit is limited on its output by internal circuitry but the code is the code
Options
All three arrays have different exposures, I wouldnt mind buying the new inverter with dual MPPT but they seem to have fallen out of favor.
Install a 110 to 220 volt step up transformer on the 1 KW unit and switch to a smaller 2 pole breaker? This balances the load and gets me below 40 amps if I install a 10 amp 2 pole breaker. At that point I would probably do a line size tap due to the cost and loss of the transformer.
Install a subpanel for PV only, have it feed a 40 amp breaker in the main panel.? This wouldnt be so bad but I am not sure the code allows this?
So anyone have any suggestions or thoughts besides shutting down the 1 KW system?
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