Regarding wire sizing

nyarelathodepnyarelathodep Solar Expert Posts: 99 ✭✭
Well, finally pulled the trigger and ordered some components at long last. To start off, phase 1 of system is 24v bank, a pair of Canadian solar poly 250s, a classic 150, and a midnite combiner box. The maximum planned upgrades will be up to another six of those same panels. The last thing to figure out is the wire sizes and breakers. Seeing as I don't want to run the wires twice, I am looking to lay the ones which will handle the eight eventual panels. The bank voltage will remain the same, so what size wire should I run from combiner box to the CC? The run is 50'. I was told the classic 150 handles up to 4awg, (is that correct? ) but I'm guessing the wire run might be at least 2awg?, and if that's the case, what is typically used to downsize the wire? And for the initial pair of panels, how should I size the breakers for the CC? Also, the phase 1 inverter is going to be a samlex 600w, either the pst or the sa... Anyone have comments on either one being a better choice?

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Regarding wire sizing

    Assuming you're talking about the wire run from the combiner box to the charge controller.

    Wire size is based on Voltage, current, distance, and how much Voltage drop can be tolerated.
    The array would probably be based on strings of two panels in series, meaning an operating Voltage around 60 (2X Vmp). Current per string would then be 8+ Amps times the number of strings - four total or about 34-36 Amps. So really you're looking at 6 AWG to get the V-drop below 3% for the full array.

    The charge controller will not have breakers: it would have one on the output to the batteries sized accordingly to the expected current. You will probably want to go 6 AWG or 4 AWG and 80-100 Amp breaker there.

    The panel strings will have a breaker sized according to their current, or more accurately their maximum series fuse rating. This is likely 15 Amps. Check the specs.
  • nyarelathodepnyarelathodep Solar Expert Posts: 99 ✭✭
    Re: Regarding wire sizing

    Oh, that's good news! will be less than i was supposing for the wires. Thanks yet again, 'coot. Only thing left now is orientating the panels.
  • nyarelathodepnyarelathodep Solar Expert Posts: 99 ✭✭
    Re: Regarding wire sizing

    Guess i have one more question about the bank to CC breaker actually (didn't realize there were so many variants), is there a particular kind to use specifically? I see din rail, panel Mount, double pole etc... was just planning on mounting it with screws to the plywood backing for the time being... noticed the panel Mount one was half the price of the din rail one.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Regarding wire sizing

    Pretty much a matter of preference and mounting convenience. They all function the same (if they meet the same parameters). In some instances code compliance is involved.
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