New setup please review

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intel415
intel415 Solar Expert Posts: 31 ✭
in Solar Beginners Corner #1
Hi guys, I just returned the morningstar mppt 15A. I'm going to with a new 12V system setup please let me know if it will work or not thanks :D

2x Mitsubishi 225W = 450W
Voc ~ 30V and ~8A
1x Rogue mppt
2x Trojan t-105
1x Morningstar 300w inverter

My load is not big probably ~400whr

my question is what kind of fuses do i need to put between the charge controller and battery and battery to inverter?

Thanks.
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  • shift
    shift Solar Expert Posts: 48 ✭
    #2
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    Re: New setup please review

    How many amps will your load be drawing? 24 or 12v battery bank?
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  • intel415
    intel415 Solar Expert Posts: 31 ✭
    #3
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    Re: New setup please review

    less than 3A on the AC side, my system will be 12V
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #4
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    Re: New setup please review

    The MorningStar inverter is good for 600 watts for ten minutes (round up to next available wire/fuse standard size)... So:
    • 600 watts * 1/10.5 volts cutoff * 1/0.85 inverter eff * 1.25 NEC safety factor = 84 Amp minimum for inverter fuse/wiring

    Check the charge controller manual, but basically:
    • 30 amps * 1.25 NEC factor = 37.5 Amp fuse/wiring rating (for maximum controller output)

    450 watt is a good sized array--Nominal expected current with fairly well charged battery bank would be:
    • 450 watts * 1/14.5 volts * 0.77 panel+controller derating = 23 Amps @ 12 VDC bank

    Regarding your battery bank, assuming standard 225 AH 6 volt battery set (2x for 12 volts)... The recommended inverter AC outputs would be:
    • 225 AH * 12 volts *0.85 inverter eff * 1/8 max cont current draw = 287 Watts @ 115 VAC max recommended continuous power
    • 225 AH * 12 volts *0.85 inverter eff * 1/2.5 max surge draw = 918 Watts @ 115 VAC max recommended surge power

    In this case, the inverter will limit your maximum surge current to ~600 watts maximum.

    Assuming you run ~9 months of the year at 4 hours of "noontime" equivalent sun per day, a 450 watt array would provide:
    • 450 watts * 0.52 over all system eff * 4 hours of sun per day = 936 WH per day of 115 VAC power

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #5
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    Re: New setup please review

    Assuming the system is installed in/around Los Angeles, using PV Watts with fixed array pointing south tilted to Latitude, your "average" hours of sun per day, by month, will be:
    Month    Solar Radiation (kWh/m 2/day)
1      4.44     
2      5.35     
3      5.62     
4      6.06     
5      6.19     
6      6.17     
7      6.48     
8      6.68     
9      5.78     
10      5.43     
11      4.84     
12      4.46     
Year      5.63

    So, even assuming 4 hours of sun per day is a low-ball number for your region.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • intel415
    intel415 Solar Expert Posts: 31 ✭
    #6
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    Re: New setup please review

    Thanks Bill, can i use 50A between the controller and 100A fuse on battery to inverter? can't really find fuses around that numbers you calculated.

    I will try to lay them flat on my roof first, sunlight is like at 75 degrees. will try different angles if needed.

    Not really worry about the inverter because i'm not going to put a heavy load on it to suck the power. Kind of lucky my roof gets more than 4 hours of good sunlight.

    Also will a 15A dc breaker work on the solar panels to charger controller? and i will use it as a disconnect switch. Panels will be connected in series ya i know the rogue is limited at 60Voc, but i don't think the panels i'm going to buy will reach exactly 30V each ~60V and ~8A.

    Thanks.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #7
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    Re: New setup please review

    Regarding fusing/breakers--Yes, just round up to the next standard size of breaker/wiring.

    And no, as far as I understand, you cannot place the two panels in series... Depending on how cold you estimate for your installation--32F for (I am guessing) your panels will be Voc-cold~79 volts. Way too high for the 60 VDC maximum array input voltage (again, just a quick look through the Rogue manual).

    Those panels are Vmp-stc~30 volts--Vmp is much lower than Voc (max power vs open circuit panel voltage).

    Usually, the panel data sheet will list the maximum series fuse for those panels... Otherwise, Isc*1.25 and rounded up to the next standard fuse is usually close.

    Note, for one or two panels, you do not need any input fuse/breakers--You could use a good quality DC switch if you wished.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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