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That clarifies that calculation.
Yes, I will have a main breaker and breakers for the two subpanels, one of which will have solar backfeed. That may be my approach since I can easily distribute the loads to the subpanels with a 50 Amp breaker and a 75 Amp breaker or a combination not exceeding 125 Amps.
My system is a work in progress and this discussion has been helpful to know that I have options to make the smaller service panel changeout work for me. My long term goal is to self consume as much as I can and only use what I sell back to the grid as a resource to charge my EVs at super off peak rates. My plan for Phase Two is to add an additional 3 kW of solar to just run the Skybox and the loads during the day. All of that will not be part of the PTO with PGE. I already have the Skybox, 42 kWh of LFP batteries and 11 Sunpower panels to power the Skybox. I want to get that investment working as soon as I can but I need to get through the PTO and then I will pull a permit for Phase Two.
So - back to the 200A panel.
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I started the conversation with PGE in early May and they could not give me an answer about whether I needed a new transformer if I were to go with a 200 Amp panel. Based on that uncertainty, I cancelled that request and started a new one with the like for like changeout. I have the solar installed and want to get the PTO so I can move on to Phase two which is to install the Outback Skybox. I am not worried about the lights dimming because the heat pump ACs that i plan on installing will all be inverter soft starts.
An earlier install I did with a professional installer three years ago on another home included a new 200 Amp panel. That proved to be a nightmare for them because they did not realize I had underground service and they had to tear out some sidewalk and dig a twenty foot trench to put 3 inch conduit for the new service. It took 18 months to complete that. I never paid a dime until I got the PTO but I did not get the benefit of the NEM solar and had to juggle my EV charging when the solar was generating. Since this is a self install I have invested the capital in the panels on my roof and want to get the PTO as soon as possible. I agree for most people the best move would be the larger 200 Amp service. Since my goal is self consumption I want to move on to Phase Two of my plan as as soon as I can.
Thanks for all the input.
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What are the subpanels?
Do you only have a main breaker, a breaker for the subpanel (for the branch circuits) and a breaker for the backfeed?
IF that's the situation, then IF all the breakers on the busbar sum up to less than (or equal to) the main breaker, I think you would be compliant.
BUT that option for being code compliant wouldn't be using the 120% * main breaker - it would be just: Is main_breaker >= (sum_of_all_other_breakers)? (And more importantly busbar >= sum_of_all_other_breakers)
This approach is the "(3)(c)" section in the code.
What are the subpanels?
Do you only have a main breaker, a breaker for the subpanel (for the branch circuits) and a breaker for the backfeed?
IF that's the situation, then IF all the breakers on the busbar sum up to less than (or equal to) the main breaker, I think you would be compliant.
BUT that option for being code compliant wouldn't be using the 120% * main breaker - it would be just: Is main_breaker >= (sum_of_all_other_breakers)? (And more importantly busbar >= sum_of_all_other_breakers)
This approach is the "(3)(c)" section in the code.
Basically there are 3 options for having it be code compliant and using the busbar, spelled out in 705.12(D)(2).
You can do 3a, 3b, OR 3c.
But you can't use part of the phrasing from 3b and part from 3c.
The AHJ is the real authority though - so if they say it's OK, they have final say.
I think they'd look at it and if it's not meeting 3a, 3b, nor 3c it's not passing inspection (or plan review if they do a plan review beforehand)
And right now I believe what you've described doesn't meet the 3a, 3b, nor 3c.
But I may not have understood your description correctly.
You can do 3a, 3b, OR 3c.
But you can't use part of the phrasing from 3b and part from 3c.
The AHJ is the real authority though - so if they say it's OK, they have final say.
I think they'd look at it and if it's not meeting 3a, 3b, nor 3c it's not passing inspection (or plan review if they do a plan review beforehand)
And right now I believe what you've described doesn't meet the 3a, 3b, nor 3c.
But I may not have understood your description correctly.
So - back to the 200A panel.
........
An earlier install I did with a professional installer three years ago on another home included a new 200 Amp panel. That proved to be a nightmare for them because they did not realize I had underground service and they had to tear out some sidewalk and dig a twenty foot trench to put 3 inch conduit for the new service. It took 18 months to complete that. I never paid a dime until I got the PTO but I did not get the benefit of the NEM solar and had to juggle my EV charging when the solar was generating. Since this is a self install I have invested the capital in the panels on my roof and want to get the PTO as soon as possible. I agree for most people the best move would be the larger 200 Amp service. Since my goal is self consumption I want to move on to Phase Two of my plan as as soon as I can.
Thanks for all the input.
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