Wiring question. which is the best way ?

Hi everyone,
I'm installing my system (8.58kw, SB8000us) and would like to know about where to place the inverter.
I have a 400 foot run from the array to the house and was planning on installing it at the array (ground mount) and running 0000 aluminum between the two which should limit my loss to 1.1 percent. (240v /32amp max). Assuming I use the same wire, is there any advantage/disadvantage to installing the inverter at the array, or should it be at the house & why ?
Thanks !!

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Wiring question. which is the best way ?

    The SB8000 runs an array Voltage of 365+ and a maximum input current of 30 Amps. Over 400 feet you should not need to run 4/0 aluminium wire. Looks to me like 6 AWG would work there, but check it with a good V-drop calculator.

    Since the array to inverter wiring is likely to be the highest Voltage at the lowest current this would be the place to put the longest wire run.
  • BB.BB. Super Moderators, Administrators Posts: 30,642 admin
    Re: Wiring question. which is the best way ?

    Another issue can be that with long wire runs from the main panel to the GT inverter you can have voltage "rise".

    If your utility voltage runs on the "high side" around 255+ VAC, the additional wire run can raise the voltage at the inverter and shut it down (around 260-264 VAC is the typical high limit for the GT inverter's output).

    Of course, using 4O aluminum wire will help reduce the wire run resistance/voltage rise issues.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JOSIJOSI Registered Users Posts: 11
    Re: Wiring question. which is the best way ?

    just done a quick voltage drop calculator and at 400 ft with 380v DC #3 awg alum will be at a 2.5% voltage drop.
  • srhillsrhill Registered Users Posts: 8
    Re: Wiring question. which is the best way ?

    Thanks everybody for the advise.
    I was concerned about the voltage rise possibility but don't really know much about it. I have a TED 5000 that has been monitoring for some time now and usually my voltage stays, between 235 - 250v. So if I use the 4/0 maybe the voltage rise won't be an issue. I supose if it did cause problems I could move the inverter to the house and "rewire" to feed dc the 400 feet, (which is probably the most desireable method) decisions decisions.......
    Any other comments glady welcomed !
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Wiring question. which is the best way ?
    BB. wrote: »
    Another issue can be that with long wire runs from the main panel to the GT inverter you can have voltage "rise".
    You always have voltage rise. The voltage at the service entrance is what it is and the always non-zero voltage drop in the wires from the inverter to the service makes the voltage higher at the inverter.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Wiring question. which is the best way ?
    ggunn wrote: »
    You always have voltage rise. The voltage at the service entrance is what it is and the always non-zero voltage drop in the wires from the inverter to the service makes the voltage higher at the inverter.

    Nit-picker! :D

    Bill means too much Voltage rise. Where the resistance of the wire between the inverter and service can allow the inverter's output Voltage to rise above the point where the inverter decides there's no utility and shuts down.

    8kW on 240 VAC is roughly 34 Amps. If we do a "reverse Voltage drop" calculation we see 4 AWG copper keeping the "V-rise" below 3% (a difference of about 7 Volts).
    Depending on what the inverter's drop specs are (264 VAC max out) and what the utility's line Voltage really is (????) this could work. You'd need 1 AWG aluminium for the same results it looks.

    Up here the aluminium wire would cost more than the copper. I'd still go with the long run on the array side for the reasons previously mentioned.
Sign In or Register to comment.