Announcement

Collapse
No announcement yet.

Wire Gauge

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Wire Gauge

    Morning guys.
    I have just put in a new system and am still trying to get my head around the mathematics of solar.
    My question is on wire gauge.
    I have just bought a 100 meter roll of insulated armored cable.
    The inner core is AWG 6 and the outer when calculated is also AWG 6
    I am using the inner as positive and outer as negative.
    I have 2 solar panels and both are 24 volts x 250 Watt each
    I have connected them in parallel
    So I have a 24v x 500 Watt array.
    My batteries ( 4 x 12v x 200 amp series and parallel =24v x 400amp ) and CC are 30/50 feet away.
    Is this wire size ok?
    Cheers
    Mike in Kenya
    cable.jpg
    Last edited by Aussiemike; 02-02-2018, 05:51 AM.

  • #2
    two 250w panels in parallel is like 20amps max which could be done with as little as 12ga wire. 10ga is recommended - your 6ga is overkill..
    BSEE, R11, NABCEP, Chevy BoltEV, >3000kW installed

    Comment


    • #3
      Appreciate your input Solarix.
      What is the max distance might I get with 12ga and is that 12ga each way? + plus -

      Comment


      • #4
        Originally posted by Aussiemike View Post
        Appreciate your input Solarix.
        What is the max distance might I get with 12ga and is that 12ga each way? + plus -
        Have a look here, mate.
        Paul

        Comment


        • #5
          Thanks Paul.
          So if I read this right and look down the 20 Amp column I should be OK from 7.6m to 12.2m with 6 ga.
          Last question.
          Is that 6ga for positive and 6ga for negative?
          ie up to 24.4 m of 6ga wire.
          Therefore the image of the wire above is OK and not an overkill as suggested by Solarix.
          Cheers
          Mike

          Comment


          • #6
            Originally posted by Aussiemike View Post
            So if I read this right and look down the 20 Amp column I should be OK from 7.6m to 12.2m with 6 ga.
            Is that 6ga for positive and 6ga for negative?
            ie up to 24.4 m of 6ga wire.
            Yes.
            Yes.
            No. The chart shows the total length (round-trip) of the run (for up to a 3% voltage drop), at 12.2 meters. It is not 24.4 meters. For 24.4 meters, it would call for 2 AWG cable, according to the chart.

            I suggest reading this link, the link SunKing posted in his "chart" thread: https://www.bluesea.com/resources/1437

            Off-topic: Where in Kenya, if you don't mind me asking?
            Paul

            Comment


            • #7
              Thanks Paul,
              I live in Tiwi Beach which is 17 kms south of Mombasa and 57 kms north of Diani Beach.
              Look me up if you are ever in the area.
              Cheers Mike

              Comment


              • #8
                Paul what fuse would you recommend for my system.

                I have 2 solar panels and both are 24 volts x 250 Watt each
                I have connected them in parallel
                So I have a 24v x 500 Watt array.
                On the back of each panel is printed Max power point 8.6A
                Short circuit 9.9A
                Cheers Mike

                Comment


                • #9
                  Would you use these?
                  https://www.ebay.co.uk/itm/Quality-M...JzNL3sEJV5Sjgw

                  Comment


                  • #10
                    How is this a CRITICAL load? Two 24V panels in parallel into a 24V battery. I smell PWM. The voltage drop is insignificant and 3 or 10% loss will have no impact on charge current. The internal resistance of the circuit board and FET are likely far more resistance than that.

                    Comment


                    • #11
                      Originally posted by Aussiemike View Post
                      No. I would use breakers. I use Midnite Solar DC breakers. I live in Cambodia. So, there is no "code" to go by, just common sense. So, I just mount mine on DIN rails.

                      din_rail_mounted_breakers.jpg


                      Originally posted by Aussiemike View Post
                      Paul what fuse would you recommend for my system.

                      I have 2 solar panels and both are 24 volts x 250 Watt each
                      I have connected them in parallel
                      So I have a 24v x 500 Watt array.
                      On the back of each panel is printed Max power point 8.6A
                      Short circuit 9.9A
                      Take the Isc (short circuit current) of the (parallel) panels and multiply it times 1.5. Round up to the nearest breaker size for each panel. In this case, the magic number is 15 amperes.

                      Whether you will need one, or two breakers / fuses, depends on how they are wired together. Are they wired together, then both have a single run to a combiner box? Or, do each of them run directly to a combiner box? The former would use one breaker / fuse. The latter would use two.

                      Paul

                      Comment


                      • #12
                        Originally posted by PNPmacnab View Post
                        How is this a CRITICAL load? Two 24V panels in parallel into a 24V battery. I smell PWM. The voltage drop is insignificant and 3 or 10% loss will have no impact on charge current. The internal resistance of the circuit board and FET are likely far more resistance than that.
                        Not that it is a "critical" load. But, he already has the cable. So, why not go ahead and use it? He could also expand the system later.
                        Paul

                        Comment


                        • #13
                          Don't pretend you are just not wrong.

                          Comment


                          • #14
                            Originally posted by PNPmacnab View Post
                            Don't pretend you are just not wrong.
                            Then why don't you enlighten me, oh anointed one.
                            Paul

                            Comment


                            • #15
                              As I am going to a lot of trouble and expense to put all this together it would make me very happy to have you guys sign off on this diagram.
                              If I understand correctly I would only need a single breaker.
                              Thanks Guys. 24v battery panel setup.jpg

                              Comment

                              Working...
                              X