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120%Rule Design Help

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  • 120%Rule Design Help

    We are designing a PV system for a home that has 84 PV modules with 4-4.8 KW inverters. Each inverter is 26.2 amps at 125% continuous load. Our plan was to install a 125 Amp 8/16 circuit load center with a 110 Amp overcurrent device as a combiner panel containing 4-30 Amp breakers for the inverters. The home has a 400 Amp service with 2-200 amp panels. The question is, how do I come out of one of these 200 Amp panels and fulfill the 120% rule? Does anyone have any other design suggestions? We are using the 2011 NEC.

  • #2
    What I am thinking is the two Electrical service panels will need to be 225 Amp buss with 200 Amp main. Feed 2 separate 4/8 circuit panels out of each 200 Amp panel with a 60 Amp overcurrent device. The kicker would be that the Electrician wiring the structure would need to size the service conductors for the 225 Amp. Any other ideas?

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    • #3
      The problem with that design is the customer owned meter. I hope you guys have some ideas on this. I have several systems similar to this where the 120% rule is really throwing a wrench in things.

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      • #4
        Do a line tap.
        Put the three inverters into a combining panel and tap that between the meter and the main breaker.
        NABCEP certified Technical Sales Professional

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