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Thread: 240V dual phase inverter?

  1. #1

    Default 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. #2

    Default 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

  3. #3

    Default Re: 240V dual phase inverter?

    Quote 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?

  4. #4

    Default 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

  5. #5
    Join Date
    Sep 2006
    Location
    Willits, CA
    Posts
    5,558

    Default 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

  6. #6

    Default Re: 240V dual phase inverter?

    Quote 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.

  7. #7

    Default Re: 240V dual phase inverter?

    Quote 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

  8. #8
    Join Date
    Aug 2011
    Location
    Hillsboro, Oregon, USA
    Posts
    12

    Default Re: 240V dual phase inverter?

    Quote 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 ^_^

  9. #9

    Default Re: 240V dual phase inverter?

    Quote 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

  10. #10

    Default Re: 240V dual phase inverter?

    Quote 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

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