60 amp Xantrex CC - 80 amp breakers?

Seanadirondacks
Seanadirondacks Registered Users Posts: 20 ✭✭
edited April 2018 in General Solar Power Topics #1
Hello I have a 60 amp Xantrex and I have 80 amp breakers on the positive lines. Are these the correct breakers or should I scale down to 60 amps? Thank you!
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #2
    The main function of the breakers is to protect the wire. That means you have at minimum  #4 AWG wire installed for these connections.

    Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • Seanadirondacks
    Seanadirondacks Registered Users Posts: 20 ✭✭
    #3
    Thanks Rick I am using #4awg wire. Im unsure if using the 80 amp breaker is the correct choice or if i should be using 60 amp breakers as the CC is 60 amp. Thanks!
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
    80A breaker is good for 4ga wire.  If your charge controller melts into a puddle of solder, when the shorting amps reach 80A, the breaker will pop, preventing the wires from causing a fire.   This happens only when the CC is already dead, if it was going to die, 60A or 80A would make no difference.  The breaker is for the wire.
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  • Seanadirondacks
    Seanadirondacks Registered Users Posts: 20 ✭✭
    #5
    Thanks Mike95490!
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #6
    BUT... if you want to send the puddle to Schneider for a warranty claim, you might want to be able to say you used their recommended breaker size ;--)
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Seanadirondacks
    Seanadirondacks Registered Users Posts: 20 ✭✭
    #7
    I was just reading the manual as its a new CC. Im gonna need #6 wire and a 60 amp breaker! I'll just step down my #4 wire from the bank using a bus bar and bring the #6 to the CC.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #8
    If the #4 wire physically fits in the controller terminals, I'd go ahead and use it (but with the recommended 60a DC rated breaker).
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Seanadirondacks
    Seanadirondacks Registered Users Posts: 20 ✭✭
    #9
    Good advice! Thanks!
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  • Horsefly
    Horsefly Registered Users Posts: 476 ✭✭✭✭
    #10
    The CC is rated for 60A continuous output.  The NEC rule says that the breaker size should be 125% of the continuous rate. 125% of 60A is 75A. Since you probably can't find a 75A breaker, the 80A is fine. I wouldn't switch it out. If you put in a 60A you will be - strictly speaking - undersizing your breaker.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 8S (25.6V), 230Ah Eve LiFePO4 battery in a custom insulated and heated case.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #11
    It also depends on which brand/model of circuit breaker you use... Most circuit breakers (and supporting wiring) should be 1.25x larger than the highest constant current you expect. For a 60 amp charge controller:
    • 60 amps * 1.25 NEC derating = 75 amps (round up to next standard size is 80 amps)
    Outback and (I think) have some breakers that are rated for max continuous load (something like 63 amps). In theory, you do not need to up rate them (but you should still use up rate the cabling to ~75-80 amps).

    Typically, breakers (and fuses) will not trip at 80% of capacity and will (eventually, minutes to hours) at 100% or rated capacity. But without spec sheets, it is difficult to be sure.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,886 ✭✭✭✭✭✭
    #12
    Schneider lists the battery circuit breaker they sell/make for the mppt 60 at 80 amps and the mppt 80 at 100 amps.

    "we go where power lines don't" Sierra Nevada mountain area
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