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  • 240V dual phase inverter?

    I currently am looking for a dual phase 240V inverter for my off grid setup at my house. I have an existing generator transfer switch installed that works great with my generator with the 4 prong twist lock plug (I forget the exact L number of it right now)

    I'm looking for an inverter or pair of inverters that will patch into my generator transfer switch to power select circuits in my home from my battery bank. Right now, my battery bank is 12V but if no such inverter exists in 12V, I'm open to changing it as well.

    Any ideas? Thanks!

  • #2

    Re: 240V dual phase inverter?

    Re: 240V dual phase inverter?

    Welcome to the forum.

    I wouldn't say there's no such thing as a 12 Volt split-phase 240 VAC inverter, but I would say you don't want one. When you're in that power range the DC Amps would be pretty high on 12 Volts.

    A couple of good brands here would be Magnum and Xantrex. Minimum would be this Magnum 24 Volt http://www.solar-electric.com/maenms4040wa1.html
    Frankly I'd prefer 48 Volt for its lower DC Amps: http://www.solar-electric.com/maenms4444wa.html

    If you need more than 4 kW then the Xantrex XW 6048 would be a good choice: http://www.solar-electric.com/xaxwhyin1.html Although it is pricey because you're paying for grid-tie ability which you won't use in an off-grid situation. Outback has a similar 8 kW unit, the Radian: http://www.solar-electric.com/rasein.html

    But what you really need to know first is how many Watts you're going to need to supply. If it's very low you can use an autotransformer on a standard 120 VAC inverter; they're good for up to 4 kW. Usually 240 goes hand-in-hand with big Watts, and it's worth getting the power from a larger inverter.

    I have one 240 Volt pump on my system, and it is run from 120 through a transformer.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

    Comment


    • #3

      Re: 240V dual phase inverter?

      Re: 240V dual phase inverter?

      Originally posted by Cariboocoot View Post
      Welcome to the forum.

      I wouldn't say there's no such thing as a 12 Volt split-phase 240 VAC inverter, but I would say you don't want one. When you're in that power range the DC Amps would be pretty high on 12 Volts.

      A couple of good brands here would be Magnum and Xantrex. Minimum would be this Magnum 24 Volt http://www.solar-electric.com/maenms4040wa1.html
      Frankly I'd prefer 48 Volt for its lower DC Amps: http://www.solar-electric.com/maenms4444wa.html

      If you need more than 4 kW then the Xantrex XW 6048 would be a good choice: http://www.solar-electric.com/xaxwhyin1.html Although it is pricey because you're paying for grid-tie ability which you won't use in an off-grid situation. Outback has a similar 8 kW unit, the Radian: http://www.solar-electric.com/rasein.html

      But what you really need to know first is how many Watts you're going to need to supply. If it's very low you can use an autotransformer on a standard 120 VAC inverter; they're good for up to 4 kW. Usually 240 goes hand-in-hand with big Watts, and it's worth getting the power from a larger inverter.

      I have one 240 Volt pump on my system, and it is run from 120 through a transformer.
      thanks for the quick reply.

      to answer your question on required wattage, well, not a lot. I have a Xantrex ProWatt SW 1000 inverter, and it has supplied all of my needs to date. My main thought was to put my array to good use in my home without having to drag wire all over the place through already finished walls and ceilings. I live in Minnesota, and it's real cold here much of the year, but I like to garden and have fresh veggies, so I built myself a little indoor garden grow area, and have some LED grow lights I want to power. There are 2 grow lights, and they draw around 65 watts each at 120V.

      I thought it would be easy to use my off grid solar array to run these grow lights and a few other things. Right now, I have 4, 6 volt ~230ah golf cart batteries setup in a 12V setup, and the Xantrex 1000 watt inverster, I use it to power lighting and tools in my garage.

      I have the input for my generator transfer switch only a few feet from my inverter in the garage, it sure would be temping to patch into it, but the inverters you posted are out of my price range, nor do I need 4000 watts (yet). using the transfer switch would make it easy to flip circuits in the house from grid to solar or generator power without hacking into any wiring.

      Can you tell me more about this auto transformer? Would it power my transfer switch without flipping the breaker?

      Comment


      • #4

        Re: 240V dual phase inverter?

        Re: 240V dual phase inverter?

        So here's the thing: do you actually need 240 VAC for anything, or are you just needing to supply both L1 and L2 on the house wiring?

        And remember that a generator that puts out 240 VAC probably has 120 VAC available if you wire it right. Usually the plug has four connections: L1, L2, Neutral, and ground. Either L1 or L2 to neutral will provide 120 VAC.

        Also, the generator is usually used to recharge batteries and carry loads with the inverter off (or in charge mode). Or you can use it to power a stand-alone charger connected directly to the batteries.

        The autotransformer: http://www.solar-electric.com/psx-240.html This is a 1:1 transformer with the two sides wound in phase. You feed 120 VAC to one side and it creates a "mirror image" 120 VAC on the other. With the "neutral" wires tied together the two 120 VAC sides "stack" to form 240 VAC across the two hot leads.

        The trouble with feeding L1 and L2 from your small inverter is the possibility that the total loads on both may exceed its capacity, even though all those loads are small.
        1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

        Ohm's Law: Amps = Volts / Ohms
        Power Formula: Watts = Volts * Amps

        Comment


        • #5

          Re: 240V dual phase inverter?

          Re: 240V dual phase inverter?

          google: Trace T240 Autotransformer (3.9KVA) (NAWS does not list it in their catalog)

          http://www.solarcellsales.com/techinfo/docs/T240.pdf
          manual with hook-up and schematics:
          http://www.wholesalesolar.com/pdf.fo...e240Manual.pdf

          An autotransformer has a single winding, usually center tapped, or tapped at selected voltage steps.


          Trace Engineering T240 autotransformer.
          This power compact unit can be used in several ways:

          Step Up: Allows you to power 240VAC loads from a single 120VAC inverter/charger. This is typically done for powering deep well pumps or other dedicated high power 240VAC loads.
          Step Down: Allows you to connect a large 120 VAC load to the output of a stacked pair of DR or SW inverters (120 / 240 VAC). This results in the inverters sharing the load, allowing higher performance and efficiency.
          Balancing Transformer: Allows a single 120 VAC inverter to be connected to a generator which has 240 VAC output. Keeps the generator balanced for better performance and operating life. Balancing the generator's output also allows higher charge rates from your battery charger.
          http://tinyurl.com/LMR-Solar
          http://tinyurl.com/LMR-BigLug
          http://tinyurl.com/LMR-NiFe

          Grundfos 10 SO5-9 with 3 wire Franklin motor (1/2hp 240V 1ph # 214505 ) on a timer for 3 hr noontime run - Runs off PV
          Powerfab poletop PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe battery | 15, Evergreen 205w "12V" PV | Midnight ePanel || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT

          Comment


          • #6

            Re: 240V dual phase inverter?

            Re: 240V dual phase inverter?

            Originally posted by Cariboocoot View Post
            So here's the thing: do you actually need 240 VAC for anything, or are you just needing to supply both L1 and L2 on the house wiring?

            And remember that a generator that puts out 240 VAC probably has 120 VAC available if you wire it right. Usually the plug has four connections: L1, L2, Neutral, and ground. Either L1 or L2 to neutral will provide 120 VAC.

            Also, the generator is usually used to recharge batteries and carry loads with the inverter off (or in charge mode). Or you can use it to power a stand-alone charger connected directly to the batteries.

            The autotransformer: http://www.solar-electric.com/psx-240.html This is a 1:1 transformer with the two sides wound in phase. You feed 120 VAC to one side and it creates a "mirror image" 120 VAC on the other. With the "neutral" wires tied together the two 120 VAC sides "stack" to form 240 VAC across the two hot leads.

            The trouble with feeding L1 and L2 from your small inverter is the possibility that the total loads on both may exceed its capacity, even though all those loads are small.
            I'm not planning on running anything 240V...in fact, in my home, only my well pump and AC use this (and draw way too much for this inverter). It's merely to be able to power both legs L1 and L2 in my panel. All loads will be 120V. You're right on the connector, L1, L2, ground, and N.

            I tried to wire up only 1 side of the transfer switch to my inverter, and even that flipped the breaker on the inverter.

            Comment


            • #7

              Re: 240V dual phase inverter?

              Re: 240V dual phase inverter?

              Originally posted by Dill View Post
              I'm not planning on running anything 240V...in fact, in my home, only my well pump and AC use this (and draw way too much for this inverter). It's merely to be able to power both legs L1 and L2 in my panel. All loads will be 120V. You're right on the connector, L1, L2, ground, and N.

              I tried to wire up only 1 side of the transfer switch to my inverter, and even that flipped the breaker on the inverter.
              That's just what I mean: trying to power everything that's on one side of system is too much for a 1 kW inverter. Not surprising at all.

              The only safe thing to do here is to set up a sub-panel with the circuits you need to run off the inverter, limited to not exceed its capacity. The trouble there is that 1 kW is less than one 15 Amp circuit. If you try to substitute that inverter for your generator (probably 3kW or more) it will be easily overloaded.
              1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

              Ohm's Law: Amps = Volts / Ohms
              Power Formula: Watts = Volts * Amps

              Comment


              • #8

                Re: 240V dual phase inverter?

                Re: 240V dual phase inverter?

                Originally posted by Dill View Post
                I currently am looking for a dual phase 240V inverter for my off grid setup at my house.
                Just so others aren't confused, I wanted to clarify that you're looking for a 3-wire, single-phase, mid-point neutral 240 volt inverter. In the U.S. though, we just refer to this as a single-phase 240 volt inverter.
                --Chris ^_^

                Comment


                • #9

                  Re: 240V dual phase inverter?

                  Re: 240V dual phase inverter?

                  Originally posted by Cariboocoot View Post
                  That's just what I mean: trying to power everything that's on one side of system is too much for a 1 kW inverter. Not surprising at all.

                  The only safe thing to do here is to set up a sub-panel with the circuits you need to run off the inverter, limited to not exceed its capacity. The trouble there is that 1 kW is less than one 15 Amp circuit. If you try to substitute that inverter for your generator (probably 3kW or more) it will be easily overloaded.
                  right, but the generator transfer switch has 3 position switches for each circuit. LINE, OFF, and GEN. Even with all the switches OFF or in LINE mode, the breaker flips. The generator transfer switch I have has 6 circuits on it that you can control. My plan was to leave 4 of them on GRID and 2 on GEN (patched into my inverter) unless my grid power failed, then I could move the inverter patch over to my generator, and power my house. So even with no load on the inverter, the breaker flips. There has to be a incompatibility with the dual phase LINE power with the single phase inverter that causes this. Plug it into my dual phase generator, and it works as designed, I can move any circuit from LINE to OFF, to GEN without any issues at all. 2 of the circuits on the transfer switch are lights, 3 are wall outlets (with nothing plugged into them right now) and one is my fridge. They are all in LINE mode right now. That's the beauty of the transfer switch, you can choose which circuits you want to run from which input.

                  This is the generator transfer switch I have:
                  http://www.amazon.com/Reliance-20216.../dp/B000HS2L1G

                  Comment


                  • #10

                    Re: 240V dual phase inverter?

                    Re: 240V dual phase inverter?

                    Originally posted by DarkStar View Post
                    Just so others aren't confused, I wanted to clarify that you're looking for a 3-wire, single-phase, mid-point neutral 240 volt inverter. In the U.S. though, we just refer to this as a single-phase 240 volt inverter.

                    no, I'm looking for a 4 wire inverter to patch into this:



                    i will admit, this whole project did throw me for a little bit of a loop :) I thought I'd be able to supply the transfer switch with a 120V common leg and it would work for any 120V circuits. I was sorely mistaken! Sorry for any confusion

                    Comment


                    • #11

                      Re: 240V dual phase inverter?

                      Re: 240V dual phase inverter?

                      120/240 VAC in the use is called "Split Phase" power with a grounded neutral.

                      If you have no 240 VAC loads to run from your inverter, and the inverter output is less than 15 amps AC, then you can simply take the L1/L2 and tie them together on the inverter input side.

                      If you have an inverter larger than 15 amps, then you run the problem of running L1+L2 at a maximum of 15 amps each, and running L1+L2 (additive) current in a common return/neutral line and overheating it.

                      With 120/240 VAC split phase, the L1 and L2 are 180 degrees out of phase. So the Neutral current is the difference between L1 and L2 (L1-L2=neutral 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


                      • #12

                        Re: 240V dual phase inverter?

                        Re: 240V dual phase inverter?

                        Looks like an L14-30 twist-lock outlet, the most commonly used one for backup generators. And to be clear, it is a 4-wire split-phase system, not single phase (there is a big difference). But for all practical purposes it acts like a single-phase system.

                        Also, you don't need an autotransformer, you can use an isolated transformer, too. Two similar beasts, which will ultimately do the same thing as long as they accept 120 in and output 120/240 split-phase. Since you may have a multi-wire branch circuit OR an oddball appliance like a combo washer/dryer that doesn't "follow the rules" you don't want to just apply the 120 volt output to both sides of a panel (same phase on both legs). That will cause "bad things". Make sure you apply split-phase like it is expecting.

                        It sounds like with your inverter you don't have a load problem, you have a wiring problem. Something is causing a dead short, flipping your breaker.
                        12 kw Generac, Honda EU3000is, 4.2 kw APC UPS powered either by battery or a Prius. Really.

                        Comment


                        • #13

                          Re: 240V dual phase inverter?

                          Re: 240V dual phase inverter?

                          Originally posted by techntrek View Post
                          Looks like an L14-30 twist-lock outlet, the most commonly used one for backup generators. And to be clear, it is a 4-wire split-phase system, not single phase (there is a big difference). But for all practical purposes it acts like a single-phase system.

                          Also, you don't need an autotransformer, you can use an isolated transformer, too. Two similar beasts, which will ultimately do the same thing as long as they accept 120 in and output 120/240 split-phase. Since you may have a multi-wire branch circuit OR an oddball appliance like a combo washer/dryer that doesn't "follow the rules" you don't want to just apply the 120 volt output to both sides of a panel (same phase on both legs). That will cause "bad things". Make sure you apply split-phase like it is expecting.

                          It sounds like with your inverter you don't have a load problem, you have a wiring problem. Something is causing a dead short, flipping your breaker.
                          L14-30 sounds right. I work in IT, and see so many different twist locks with UPS's and PDU's in server racks that I can't keep them straight any more.

                          thanks for the terminology info on the split phase 240V. I agree with you on the 'odd ball' appliance thing. I did forget to add, that if I wire only 1 single circuit to the transfer switch (including the ground and neutral wires), and then connect L1 and L2 together, and the circuits ground and neutral, it works fine. When I connect the neutral and ground to the buss bars in my electrical panel, that's when the breaker on the inverter flips. That makes sense with the split phase issue.

                          So the transformer will allow me to input 120V single phase and output 240V split phase?
                          Last edited by Dill; November 4th, 2011, 10:47.

                          Comment


                          • #14

                            Re: 240V dual phase inverter?

                            Re: 240V dual phase inverter?

                            Originally posted by Dill View Post
                            ....
                            So the transformer will allow me to input 120V single phase and output 240V split phase?
                            I belive so, I know the T-240 will, and I suspect the PSX-240 will also. PSX-240 handles higher power too.
                            http://tinyurl.com/LMR-Solar
                            http://tinyurl.com/LMR-BigLug
                            http://tinyurl.com/LMR-NiFe

                            Grundfos 10 SO5-9 with 3 wire Franklin motor (1/2hp 240V 1ph # 214505 ) on a timer for 3 hr noontime run - Runs off PV
                            Powerfab poletop PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe battery | 15, Evergreen 205w "12V" PV | Midnight ePanel || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT

                            Comment


                            • #15

                              Re: 240V dual phase inverter?

                              Re: 240V dual phase inverter?

                              Is this a MSW or TSW inverter? The Modified Sine Wave inverters, typically, do not like to work with a grounded AC neutral system (when combined with a grounded battery bank, you get a dead short through the inverter).

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

                              Comment

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