FM80 cc ratings and string sizing tool

konstantin.neo
konstantin.neo Registered Users Posts: 19 ✭
in Solar Beginners Corner #1
I am using the string sizing tool on the outback site and what caught my attention is that the specification for the FM80 say 5000watt Maximum Solar Array STC Nameplate and the sizing tool limits to 4000watt, anyone know why ?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: FM80 cc ratings and string sizing tool

    Probably a trick of mathematics:
    48 Volts * 80 Amps = 3840 Watts (4000)
    3840 Watts less 77% typical derating = 4987 Watts (5000)

    That is a guess; Outback designed the string calculator, not me. :D
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #3
    Re: FM80 cc ratings and string sizing tool

    There is also the NEC wanting to derate the input current by 1.25*1.25 (80 amps/1.252 = 51.2 amps).
    • 51 amps * ~70 Vmp minmum = 3,570 watt

    It is not always clear what NEC is trying to do... But, if the device is designed to handle 80 amps input (or output), the wiring should be 1.25*80a=100 circuit and fuses...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: FM80 cc ratings and string sizing tool

    Here's another way of looking at it which might be clearer:

    A 5000 Watt STC array usually operates on average at about 80%, which is 4000 Watts.
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