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  • Multiple smaller gauge wire instead of a single large gauge wire?

    I bought a spool of #10 wire at a reasonable price so I've crimped together 5 wires to use as a supply cable for an inverter. This is probably not normal practice, so are there any drawbacks or dangers of using multiple smaller conductors as opposed to a single big one?

  • #2
    Fire comes to mind.
    MSEE, PE

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    • #3
      Being against the code also comes to mind so when the fire breaks out the insurance coverage burns up and goes away along with everything else that catches fire.
      NABCEP certified Technical Sales Professional

      [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

      [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

      [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

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      • #4
        Parallel wires are as much trouble as parallel batteries. Don't do it, get the proper size wire to begin with. Use the link to the spreadsheet in my .sig to calculate what size you need.
        Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

        solar: http://tinyurl.com/LMR-Solar
        gen: http://tinyurl.com/LMR-Lister

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        • #5
          Originally posted by Naptown View Post
          Being against the code also comes to mind.
          It is not allowed by code because of the fire danger. Well it is allowed if certain conditions are met. But there is no condition to allow parallel wiring in solar systems.
          MSEE, PE

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          • #6
            individual runs?

            Could the 10 gauge wires not be used to extend the individual wiring if they are form the panels into the charge controller? As long as the voltage loss is kept less than 3%? I did this to bring my panels into the charge controller. Each panel is wired into an individual 10 ga wire and all run through a 2" schedule 40 conduit. I agree they should not be tied together and used in lieu of a larger gauge wire where the larger gauge is needed. There are many uses for 10 gauge wire in a solar configuration Where it can be used is defined by the system and the type of insulation/covering of the wire.
            4 sets of Harbor Freight 45-watt panel kits (2 sets in series to make 24v), 3 Trina 185w 24v modules, 1 Suntech 180w module, 1 Unisolar PVL-144, 4 Optima AGMs (D34) in parallel 12-volt, 4 Concorde PVX 4050HT 6v 405 ah in series 24-volt, 2 Rogue MPT3024's, Morningstar MPPT15L, Morningstar 300-watt PSW Inverter, Samlex 1750-watt MSW inverter, various 12volt appliances and lights throughout the house.

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            • #7
              The OP was referring to the cable I assume between the battery and the inverter not string cables.
              What you did is OK as long as you have a combiner box (fused for each string) if you have more than 2 strings.
              NABCEP certified Technical Sales Professional

              [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

              [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

              [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

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              • #8
                Oops

                My apologies. I did not absorb the OP completely. Using several smaller gauge wires in lieu of the correct size wire is not recommended. How do you know what gauge you are replicating? It is best to go with the appropriate sized wire for the amps and distance. I will go back to my corner now.
                4 sets of Harbor Freight 45-watt panel kits (2 sets in series to make 24v), 3 Trina 185w 24v modules, 1 Suntech 180w module, 1 Unisolar PVL-144, 4 Optima AGMs (D34) in parallel 12-volt, 4 Concorde PVX 4050HT 6v 405 ah in series 24-volt, 2 Rogue MPT3024's, Morningstar MPPT15L, Morningstar 300-watt PSW Inverter, Samlex 1750-watt MSW inverter, various 12volt appliances and lights throughout the house.

                Comment


                • #9
                  Originally posted by firerescue712 View Post
                  My apologies. I did not absorb the OP completely. Using several smaller gauge wires in lieu of the correct size wire is not recommended. How do you know what gauge you are replicating? It is best to go with the appropriate sized wire for the amps and distance. I will go back to my corner now.
                  Happens to me all the time
                  NABCEP certified Technical Sales Professional

                  [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

                  [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

                  [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

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                  • #10
                    Thanks, for the replies.

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                    • #11
                      Would it be possible to fuse each of the 5 #10 wires with 20 Amps on the supply side and be safe? I've have inverters that used multiple fuses would this not be similar?
                      5*20A = 100 Amps?

                      Looks like I'll install the inverter closer to the battery and use a heavy duty relay as a remote control.

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                      • #12
                        It would be safer but not by much and other problems arise.
                        A little corrosion thus a higher resistance connection on one wire will cause an overload on the others and cause a cascading of the fuses blowing as current will be transferred to the other wires.
                        Besides it is not legal to do.
                        NABCEP certified Technical Sales Professional

                        [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

                        [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

                        [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

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                        • #13
                          My solar power system design calls for two 2/0 12" cables connecting each battery in the string (twenty-four 2-volt batteries to make 48V) Is this in violation of the NEC?

                          Also, it calls for 1000 MCM for the cables from the battery bank to the battery combiner box. I've been told I can use two 300 MCM cables to replace one 1000 MCM. Does THIS violate NEC?

                          Thanks!

                          Jim

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                          • #14
                            Jim per code to qualify for exemption to parallel conductors require them to be 1/0 or larger. So as long as your cables are 1/0 or larger, you are OK. There are some other qualifiers which I do not think apply to your installation. Example if you were to use a raceway, all phase conductors and a EGC have to be in the same raceway. Only time you see that is with Poly-Phase AC circuits like 3-phase. Example a 1200 amp 480/277 service would use 3 raceways, one for each phase, and each condduit would require say 2-hot, 2 neutral, and 1 EGC of the same phase.

                            Question I would have for you is why 2/0 in intercell connectors and 1000 for the combiner? Is distance the driving factor. If you start a thread with details I bet I can say you some big bucks.
                            MSEE, PE

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