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  • 80 amp AC breaker for large guage wire

    My inverters (parallel outback 2012's) are supplying AC power to three separate buildings: a garage, a guest house, and main house. I'm currently using a Square-D QO panel to distribute power from the inverters to the guest house and garage sub panels.

    My main house is under construction and nearly completed. The wire run to the main house is about 130 feet from the distribution panel and will require large guage wire (2/0). I'm having difficulty finding circuit breakers with lugs that will accept larger than #2 wire. I need to find a 60 amp breaker that will accept 2/0 wire, or a method to use a standard 60 amp breaker to supply 2/0 wire.

    Any suggestions were to find 60 or (80 amp) AC circuit breaker that will accept 2/0 wire? I would prefer something compatable with Square-D, but if there's no choice, I can change out the distribution panel to another brand that has the breakers I need.



    Thanks.
    Off grid 3.6 Kw solar, 2968Ah AGM's, Outback combiners, 4 FM80's, parallel FX2012's, Midnight solar E-Panels, Hub, Mate, Trimetric, Generac 14kw backup generator.

  • #2

    Re: 80 amp AC breaker for large guage wire

    Re: 80 amp AC breaker for large guage wire

    Guess I'm curious WHY you want to run 2/0 ?

    The most two 2,000w inverters will put out is 33amp@120v

    130' /120v/34amp using #2 alum = 2% voltage drop......switch to copper, and it's 1.2%

    Get a Hub, and set up your two inverters as master/slave, put out true 240v, and you could cut the above in half again.

    Is there more to the story ?
    20-175watt Solarworld panels, mounted on two home built single axis powered trackers, 10-245w Solarworld panels, mounted on home built dual axis tracker, 1 MX60, 1 FM60, 1 FM80, 24v bank of Absolyte 2v AGM GNP II cells 1200amp/hr, 2-GTFX2524 2500w Outbacks producing 120/240 AC, Trimetric monitor, Grid tied, produce about 600kw/hrs/mo. 12/2012: Added 10 Solarworld 255w panels and 10 Enphase mirco inverters.

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    • #3

      Re: 80 amp AC breaker for large guage wire

      Re: 80 amp AC breaker for large guage wire

      using 2/0 wire is insane unless you got it for free. As already posted the losses using copper and #2 is insignificant and when you consider that its very unlikely the inverters will be supplying more than about 80% most of the time makes it even less of a concern.

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      • #4

        Re: 80 amp AC breaker for large guage wire

        Re: 80 amp AC breaker for large guage wire

        I have no desire to use 2/0 wire, believe me. I was just going by the instructions that state: "All AC wiring from the AC source and to the AC loads must collectively handle 120 amps or more." Obviously I'm not completely understanding something. So...basically for two parallel 2012 inverters, the max output I can expect is 33 amps at 120 volts, and I should wire accordingly? That would make me a much happier person and save a ton of $$
        Off grid 3.6 Kw solar, 2968Ah AGM's, Outback combiners, 4 FM80's, parallel FX2012's, Midnight solar E-Panels, Hub, Mate, Trimetric, Generac 14kw backup generator.

        Comment


        • #5

          Re: 80 amp AC breaker for large guage wire

          Re: 80 amp AC breaker for large guage wire

          It sounds like that is a requirement for the Main Drop from the power pole requirement. Is there ever a chance that the home will have utility power?

          If so, get a regular AC Main panel (which will accept 2/O wire) and wire up the inverters as branch circuits with standard 20 amp breakers (or whatever make sense for your needs). Leave the main meter blank on the panel (that will confuse the heck out of every one).

          For voltage drop--using a generic voltage drop calculator:
          • 120 volts, 3% maximum voltage drop (3.6 volts), 33 amps -> 4 awg @ 33 amps and 130 feet (one way run) gives 2.6 volt drop

          The above assumes that you want 100% of the maximum current available 130 feet away. Obviously, if you need less current (say 15 amp branch circuit), you could use smaller gauge wire.

          -Bill
          20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

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          • #6

            Re: 80 amp AC breaker for large guage wire

            Re: 80 amp AC breaker for large guage wire

            Originally posted by Bigwooo View Post
            I have no desire to use 2/0 wire, believe me. I was just going by the instructions
            Whose instructions ?

            Originally posted by Bigwooo View Post

            So...basically for two parallel 2012 inverters, the max output I can expect is 33 amps at 120 volts, and I should wire accordingly?
            Yep.

            AND like I said, buy an Outback Hub, and the two inverters can be set up to produce 240, and you can get by with #6 copper.....cause that's exactly what I'm doing over about the same distance.

            Then, when you get it to the panel in the house/garage/etc, you split the two wire 240 onto separate bus bars in the panel, and pick up 120v off either......PLUS you have 240v should you need it for something ( like a well pump ).
            20-175watt Solarworld panels, mounted on two home built single axis powered trackers, 10-245w Solarworld panels, mounted on home built dual axis tracker, 1 MX60, 1 FM60, 1 FM80, 24v bank of Absolyte 2v AGM GNP II cells 1200amp/hr, 2-GTFX2524 2500w Outbacks producing 120/240 AC, Trimetric monitor, Grid tied, produce about 600kw/hrs/mo. 12/2012: Added 10 Solarworld 255w panels and 10 Enphase mirco inverters.

            Comment


            • #7

              Re: 80 amp AC breaker for large guage wire

              Re: 80 amp AC breaker for large guage wire

              Thanks TnAndy & BB. I do have a hub as it's required for a parallel configuration also. I don't really anticipate the need for 240 volts and I'm supplying power to three buildings: A main house, guest house, and garage/workshop. I'd like to keep the available amps higher in case I'm using power in the shop while both houses are occupied.

              Even though the max amp output in parallel is 33 amps or so, I don't understand why the instrucions on page 28 for the FX inverter state that the wiring capacity must equal 60 amps. Maybe it is a requirement for the Main Drop from the power pole, but I'll never be grid tied so that's not an issue. That 60 amp figure is why I was planning to use the larger guage wire.

              I think I'll use the 33 amp figure for calculating wire size. You just saved me a lot of $$....thanks.
              Off grid 3.6 Kw solar, 2968Ah AGM's, Outback combiners, 4 FM80's, parallel FX2012's, Midnight solar E-Panels, Hub, Mate, Trimetric, Generac 14kw backup generator.

              Comment


              • #8

                Re: 80 amp AC breaker for large guage wire

                Re: 80 amp AC breaker for large guage wire

                Originally posted by Bigwooo View Post
                I do have a hub as it's required for a parallel configuration also. I don't really anticipate the need for 240 volts and I'm supplying power to three buildings: A main house, guest house, and garage/workshop. I'd like to keep the available amps higher in case I'm using power in the shop while both houses are occupied.
                1. That's not a lot of power to run 2 houses and a shop on to begin with.

                2. By going to 240, you don't "loose" any amps.....you merely split them between 2 legs of 120v.....means each wire can carry 1/2 the amp load of a single 120v wire, meaning you get to downsize the wire even more......AND, as a bonus, probably have less voltage drop.

                Just wanting to make sure you understand that clearly, as I sensed some confusion in your answer....or, maybe, my understanding of your answer...Quien Sabe ? ........ahahahaaa
                20-175watt Solarworld panels, mounted on two home built single axis powered trackers, 10-245w Solarworld panels, mounted on home built dual axis tracker, 1 MX60, 1 FM60, 1 FM80, 24v bank of Absolyte 2v AGM GNP II cells 1200amp/hr, 2-GTFX2524 2500w Outbacks producing 120/240 AC, Trimetric monitor, Grid tied, produce about 600kw/hrs/mo. 12/2012: Added 10 Solarworld 255w panels and 10 Enphase mirco inverters.

                Comment


                • #9

                  Re: 80 amp AC breaker for large guage wire

                  Re: 80 amp AC breaker for large guage wire

                  As Andy says--If your loads are not 33 amps of 120 VAC going to one machine but, for example 20 amps going to two or more units and you can balance the loads across a 120/240 VAC circuit--It would be much less copper/voltage drop.

                  Regarding 60 amps--Most inverters can surge 2x of their rated power for a few cycles to 10 minutes or more--It is possible that these inverters will supply several minutes of 2x rated current.

                  Also, remember if you have motors with poor power factor, it is possible that the inverters VA rating (volts*amps) is higher than it power rating (volts*amps*power factor)--Which would also dictate larger wire (PF of 0.6 for induction motors is not unusual). Wiring/breakers should be rated for V*A usage with alternating current.

                  -Bill
                  20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

                  Comment


                  • #10

                    Re: 80 amp AC breaker for large guage wire

                    Re: 80 amp AC breaker for large guage wire

                    The instructions refer to how to wire it for the full rated capacity of the pass-through circuit.

                    The NEC allows inverters to feed a circuit with a higher rating than the inverter can produce. This allows fairly small inverters to provide back-up power to loads which are usually fed by a larger source. (ie. utility or generator)

                    Outback FX inverters have a 60 amp internal transfer switch regardless of the inverter's rated output. (The Mobile versions specify a 30 amp circuit.)
                    A 60 amp AC load panel can hold several typical residential branch circuits. Especially if it is a 120/240 vac subpanel.

                    The NEC article 230 requires that the minimum size for overhead and underground service conductors be a minimum of #8 copper or #6 aluminum. I have found building departments and inspectors who have interpreted this to serve as a mimimum service entrance rating. I've also had the AHJ (authority having jurisdiction) require that all residences have a metered service entrance with a minimum 60 amp breaker and circuit size.

                    For off grid, as far as function is concerned, it needs to be rated for the maximum available power which is not always obvious. You may think your wire may have to be sized at 125% of your largest source. Beware. The inverters by the company-formerly-known-as-Trace can actually add the inverter's output to the generator (or grid) output and exceed the rating of either.
                    Last edited by SolaRevolution; February 25th, 2012, 8:07.

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                    • #11

                      Re: 80 amp AC breaker for large guage wire

                      Re: 80 amp AC breaker for large guage wire

                      Originally posted by TnAndy View Post
                      1. That's not a lot of power to run 2 houses and a shop on to begin with.

                      2. By going to 240, you don't "loose" any amps.....you merely split them between 2 legs of 120v.....means each wire can carry 1/2 the amp load of a single 120v wire, meaning you get to downsize the wire even more......AND, as a bonus, probably have less voltage drop.

                      Just wanting to make sure you understand that clearly, as I sensed some confusion in your answer....or, maybe, my understanding of your answer...Quien Sabe ? ........ahahahaaa
                      Being quite amature at solar and istallation of, you just explained something I've had a hard time grasping. Sticking to the strict definition of parallel (2xamps, same voltage) vs series (2x voltage, same amps), I never considered that the 240 load would be balanced across the legs, thus no real decrease in amps. Thank you, the fog just cleared.

                      As far as running two houses and a shop, I hope it won't be a problem as the guest house won't be occupied that often. I'ts power consumption is purely low watt lights, a ceiling fan, and water pump. The shop/garage will be low use also, only when I get the idea for some project or another.

                      I think I will re-wire for 240 when I add power to the main house, makes more sense now.

                      Thanks
                      Off grid 3.6 Kw solar, 2968Ah AGM's, Outback combiners, 4 FM80's, parallel FX2012's, Midnight solar E-Panels, Hub, Mate, Trimetric, Generac 14kw backup generator.

                      Comment


                      • #12

                        Re: 80 amp AC breaker for large guage wire

                        Re: 80 amp AC breaker for large guage wire

                        You almost have it , Bigwooo.

                        Watts = Amps x Volts
                        1200 Watts at 120 volts = 10 amps
                        1200 Watts at 240 volts = 5 amps

                        1200 Watts at 48 volts = 25 amps
                        1200 Watts at 24 volts = 50 amps
                        1200 Watts at 12 volts = 100 amps

                        For a constant amount of power (Watts) if the volts are increased, the amps decrease. If the voltage decreases, the amps increase.

                        120/240 vac, "split phase" output requires 3 current carrying wires plus a ground wire. Line 1 (leg one at 120 vac) Line 2 (leg two at 120 vac) and N (neutral shared between L1 and L2)

                        The one problem with running two seperate 120 volt inverters in series as split phase 120/240 vac is that each inverter only powers one leg and so each leg only has the potential of one inverter. If your loads are not evenly distributed between the two legs you can over load one inverter quite easily. This is where an Auto-Transformer can be useful. An Auto-Transformer can "balance" the power between the two inverters by allowing current to flow from one leg to the other. The down side is that an Auto-Transformer consumes some current just by being connected to the circuit. (typically < 15 Watts) A single inverter with a 120/240 vac "split-phase" output can balance the two legs internally.

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                        • #13

                          Re: 80 amp AC breaker for large guage wire

                          Re: 80 amp AC breaker for large guage wire

                          After much thought I've decided to keep the system parallel and run 2 guage wire. The logistics of converting to 240 and adding the auto transformer (space and re-wiring considerations) just doesn't seem practical. Getting rid of the 2000 watt inverters and buying a single larger inverter witn 120/240 split-phase output is also logistically very difficult. Re-calculating my power use again and again shows that I have plenty of power to run what I will have with the parallel 2000 watt inverters.

                          I do have a question on grounding...If I'm running 2 guage wire from the distribution panel to the house (140 foot run), how do I calculate what size ground wire to use?

                          Thank you everyone for your input
                          Off grid 3.6 Kw solar, 2968Ah AGM's, Outback combiners, 4 FM80's, parallel FX2012's, Midnight solar E-Panels, Hub, Mate, Trimetric, Generac 14kw backup generator.

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