Do I need to upgrade my main service panel?

bsjaffa
bsjaffa Registered Users Posts: 2
I have been reading up on the 120% rule and am not sure if the system I have designed will require an upgrade to my main service panel.  Any assistance would be greatly appreciated.

I will be installing a 9.28 kW system with a SolarEdge SE7600H-US Inverter (the model with an EV charger).  I built my home 6 years ago and looking at my city permit paid for a 200 Amp service from the utility company.  I believe my main service panel has a 150 A main service breaker that feeds my subpanel in my basement along with the majority of my breakers installed there.  There are a few extra breakers installed in my main service panel.  The labeling on my main service panel states "Mains 250 A max".  Attached are pictures of my main service panel with the cover off and the label information.

My understanding is that the formula goes Busbar Rating * 120% - Main Service Breaker = Max Size of Inverter Breaker.  So in my case does this mean 250 A * 120% - 150 A = 150 A?  Which would be plenty big for a 40 A breaker for my system?




Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Welcome to the forum BSJ,
    ou 
    As I understand the code, you are correct... However, your drop is 200 Amp maximum, so you probably could not install a 250 Amp breaker--Just the 200 amp max. But, yes, you should be able to keep the 150 Amp breaker and install a 40 Amp breaker and all will work well.

    You would install the GT Solar breakers at the opposite end of the bus from the main breaker.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bsjaffa
    bsjaffa Registered Users Posts: 2
    Thank you for the confirmation!
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    I’m not sure how you would install the solar breaker at the opposite end of the buss from the Main, given that the main is in the middle.  You probably have to move the main as well.  Tony
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Given that the main is currently 150 Amps in a 250 Amp rated box, I would suspect that there is no issue where the 40 amp GT solar branch circuit breaker is installed (at no time/place can 150 A main + 40 A GT = 190 amps exceed the 250 A rating of the bus bars and enclosure).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    BB. said:
    Given that the main is currently 150 Amps in a 250 Amp rated box, I would suspect that there is no issue where the 40 amp GT solar branch circuit breaker is installed (at no time/place can 150 A main + 40 A GT = 190 amps exceed the 250 A rating of the bus bars and enclosure).

    -Bill


    Looking at the schematic in the top image the 150A main is actually a parrallel 4 pole breaker which is in effect a 300A breaker since current flow is divided equally in a parallel circuit. Being the maximum service, and combined branch circuit current  allowable is 250A  the breaker rating is 240A continuous, or 80% of 300A. Thoughts? 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    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.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Hmmm... I don't know. But this looks like it may be the service for a multi-unit building (i.e., bring AC mains in top, run down to meter for first unit, and add a second box below and power from Li/L2/Neutral bypass lugs...

    -Bill ??? B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mvas
    mvas Registered Users Posts: 395 ✭✭✭
    edited August 2019 #8
    That is a "Solar Ready" Combination Service-Entrance Panel.
    The Dual Pole Breaker from the Grid-Tie Inverter goes into that special TOP SLOT,
    that connects directly to the bus between the Meter and the Main Breaker = Line Side Tap. 
    Yes, it with take a Dual Pole 40 Amp Breaker ( 50 amps max per the label ).