Main panel or subpanel connect

I have a 200 amp main panel as well as a 200 amp subpanel in my house, separated by about 60' of wire run. Are there code or other requirements that a solar system tie directly into the main panel? From a logistical view it'd be much easier to tie into the subpanel. Any significant issues to suggest doing otherwise?


  • BB.BB. Super Moderators, Administrators Posts: 28,994 admin
    Re: Main panel or subpanel connect

    I think that the code for my area (California) was that I needed a 125 amp minimum main service for my 3 kWatt system (a pair of 20 amp breakers for my solar service). Makes sense that the 200 amp sub panel now has a 200 amp breaker coming in, plus a another generator source of 20 amps or so--You would not want to connect that solar inverter to a 40 amp service--you would could over-heat it by running beyond rated loads for the breaker load center. So, a 200 amp sub panel should not be a problem.

    Check the NEC and/or local building codes to be sure.

    What you will probably need is lockable (by a padlock a utility worker can apply) solar AC disconnect somewhere accessable to the power company (not behind fence with dog--usually near the electric meter). That may change where you will want to wire the solar grid-tied inverter into your home.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Main panel or subpanel connect

    NEC 690.64(B)(2) states you can feed 120 % of the panels named rating for a residential system. So as an example in a 100 amp service you can have a 20 amp breaker. The lockable AC disconnect is required to be within 10 feet of the meter.

    Some good reading.....
  • RoderickRoderick Solar Expert Posts: 253 ✭✭
    Re: Main panel or subpanel connect

    It's also worth checking the interconnect agreement with your local power utility, who may impose other restrictions, such as how high off the ground the disconnect switch must be, or even what model of switch is ok to use. PG&E, for example, actualy had a list of approved switches. They gave blanket approval to some manufacturers, but only seemed to allow certain models from other manufacturers.
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