using a voltage drop caculator for 240 volts.

I have two outback inverters. Each puts out 120 volts. When stacked this is a 240 volt output. when using a voltage drop caculator;
1. 4000 watt load is 16 amps at 240 volts.
2. 4000 watt load is 8 amps at 120 volts times two.

For voltage drop to size wire, do I Type the numbers for number 1. or 2.?

For fusing, a 20 amp fuse or 10 amp?

Thanks
gww

Comments

  • offgrid me
    offgrid me Solar Expert Posts: 119 ✭✭
    Re: using a voltage drop caculator for 240 volts.

    Watts divided by volts is amps. If you have two 2000watt inverters stacked you would have 4000w of available power whether at 240 or 120v. If this is at 240v it would be just over 16.6amp. If at 120v this would be just over 33.3 amp. By stacking you double the power by doubling the voltage, there by being able to send double the power on the same size conductor. You would want to use 12awg with a 20amp fuse at 240v for 4000w of power.
    Ned
    Just noticed from your sig that you have two 3600w inverters. This would be 7200w. At 240v this is 30amp so figure on at least 10awg with a 30a breaker
  • gww1
    gww1 Solar Expert Posts: 963 ✭✭
    Re: using a voltage drop caculator for 240 volts.

    Offgridme
    Thanks for the responce. I was just thinking that the 240 was a 4 wire run and 120 would be run with two wire. I could series some pv to 240 volts and run it with two wires. If I stack the inverters I will have 4 wires for 240 volts. So 4000 watts could mean quite a differance when fusing and making long wire runs. I just wondered how to handle this when using a voltage drop caculator.

    Does this question make sense?

    Thanks
    gww

    I guess the question should be; When using a voltage drop caculator is it caculating 4 wire run or is it caculating a two wire run for 240 volts?

    Also, the picture of your aray looks great. Did you use metal on wood or just wood to mount your panels to?
  • offgrid me
    offgrid me Solar Expert Posts: 119 ✭✭
    Re: using a voltage drop caculator for 240 volts.

    Ok so are we talking about the DC run from the combiner box to the charge controllers? If so this would be figured as a two wire run. To figure this you would input the total length of your run and the voltage your panels are wired for. Both charge controllers you have are rated for a max voltage of 150 so do not exceed this. You really want the panels wired series parallel so you have around 70v for a 48v battery bank. This would be around 57amps so you are going to need some pretty heavy wire 6 or 4 awg.
    The only wood in my mount is for the bottom and top beams. The rest is galvanized steel unistrut and home made aluminum clips. It has survived one hurricane and a blizzard so far with no damage.
    Ned
  • gww1
    gww1 Solar Expert Posts: 963 ✭✭
    Re: using a voltage drop caculator for 240 volts.

    Ned
    This question came to my mind while reading answers to an older post that I had requested and gotten lots of help on.

    http://forum.solar-electric.com/showthread.php?17559-New-install-questions/page5

    I am doing pv at 88 volts from the combiner box 200' to the dc breaker box. I am going to use 4/0 aluminum wire for this run.

    From the ac main panel in a garage to the inverter and then 240 volts at 60' plus to my basement.

    I think I understand by your answer that the 240 volt run to my basement would be entered in the voltage drop caculator as a two way wire run.

    The manual for the inverter calls for a maxamum 60 amp breaker in the houses ac feed to the inverter.

    Thanks
    gww