wire run

ws9876
ws9876 Solar Expert Posts: 448 ✭✭✭
in Off Grid Solar & Battery Systems #1
would you run a wire from inverter to Mains that was 70 ft long??
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    A little more information?

    Is this a grid tied inverter? Running at 240 VAC? What wattage of solar array/GT inverter? What voltage do your AC mains typically run at? Usually GT inverter are set to fault at ~260-264 VAC--Need to calculate voltage "rise" from GT inverter to main panel + typical "high line limit" for AC mains.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ws9876
    ws9876 Solar Expert Posts: 448 ✭✭✭
    #3
    120 volt 3000 watt inverter...no grid tie..USA mains 120/240 split disconnected using as a 120 volt service panel
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    You want to send 120vac @ 3,000 watts to your local ac service panel 70 feet from the inverter?

    What are ac loads like? Big well pump, electronics, mixed load (ie pump starts and reboots computer?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ws9876
    ws9876 Solar Expert Posts: 448 ✭✭✭
    #5
    yea...so what??? it would probably be mostly less than 1000 watts but sometimes more....would no. 2 gauge be all right??
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #6
    Generally speaking 2 gauge would be over kill, 8 gauge in general would be fine, I run mostly <500 watts and have 80' of 10 gauge, some of the wire runs in the home are 60 feet of 14 gauge on top of the run from inverter to main(now a sub panel with the neutral-ground bond made next to the inverter). I do run a window air at about 500 watts as well as the fridge most of the summer and a water heater which is 4 feet from the old main at 900 watts. Even run 1500 watt load from time to time in the kitchen at 80 + 50 feet of 12 gauge(I think).
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #7
    Might be a bit kinder to Bill, he wants to get a grip on your loads so he'll know how much current you will be running through that 70 foot run...

    It is the logical question. You can figure a steady load possible of 3000 watts / 120 volts = 25 Amps with voltage drop perhaps 30 amps, plug 30 amps AC into a wire gauge calculator...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • scrubjaysnest
    scrubjaysnest Solar Expert Posts: 175 ✭✭✭
    #8
    More info gets a more accurate answer. FWIW I use 8 awg for 30 amp RV power @ 100 feet and 10 awg for 20 amp @ the same distance. Larger then code but but handles start up surge better.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #9
    Besides trying to figure out the current.... I was also asking because if you have a combination of Well Pump plus a computer... The well pump starting can cause your computer to brown out/reset. I would have suggested that you may want to run two wire runs. One for the well pump and a second for lights/computer/etc.. loads.

    Voltage drop calculator:

    http://www.calculator.net/voltage-drop-calculator.html

    15 amps on 70' run with 10 AWG cable:

    Voltage drop: 2.10
    Voltage drop percentage: 1.75%
    Voltage at the end: 117.9

    If you have a 100 foot 10 or 12 AWG extension cord, you can try running your loads and make sure all is OK (loads start, lights don't flicker, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ws9876
    ws9876 Solar Expert Posts: 448 ✭✭✭
    #10
    actually it looks like it will be 85 ft so I would use 6 ga i guess. thanks
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