Yet another auto transformer question.

verdigo
verdigo Solar Expert Posts: 428 ✭✭
in Solar Beginners Corner #1
I have my GVFX 3648's AC out connected to a PSX-240 auto transformer and wired to step up the GVFX's 120 volt ac to 240 volts ac. This lets me power both L1 and L2 of the house's load center without the using a sub-panel for critical loads. The GVFX puts out 30 amps, but the PSX-240's output is 25 amps per leg of the 240 volts. Or at least it's two built in breakers are 25 amps each.

I understand I will never have more than 30 amps from the GVFX. My question is will the PSX-240 in this configuration give me at least 30 amps combined across both legs, and will it balance uneven loads across both legs up to 30 amps? Example would be a 5 amp load on L1, and a 25 amp load on L2.

Thanks

Dennis
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Yet another auto transformer question.

    No because you will have some losses with the transformer so the full 30 Amps won't be available.

    But otherwise yes the combined loads for L1 to N and L2 to N will balance; that's the natural of an autotransformer.

    Don't expect to run a 25 Amp load off a 25 Amp breaker either, even with nothing on the other leg.
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #3
    Re: Yet another auto transformer question.

    Okay so ignoring losses for the sake of the question two 15 amp loads? One on L1 and the other on L2?
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #4
    Re: Yet another auto transformer question.
    verdigo wrote: »
    Okay so ignoring losses for the sake of the question two 15 amp loads? One on L1 and the other on L2?

    You got it! Double the voltage with a transformer and the amperage cuts in half, watts stay the same. (Ignoring all losses of course)
    You could run a single 15 amp 240 volt load, or two 15 amp 120 volt loads off the transformer output. (Again ignoring all normal losses)
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: Yet another auto transformer question.

    You can think of it in terms of Watts: 30 Amps @ 240 Volts is 7200 Watts. Divide it up by two 120 Volt circuits and you can have any combination between the two so long as it doesn't exceed 7200 Watts. So you could have either 3600 on each or 5000 on one and 2200 on the other.

    In theory.
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #6
    Re: Yet another auto transformer question.

    I originally bought the PSX-240 when I thought I was going with an XW inverter. I found it on line for 399.00 with free shipping and I felt that was a good deal. I didn't wind up with the XW system but I am glad I got the PSX-240. It's really a handy piece of equipment. I have never understood why one would want to down convert 240 to 120 though since you can just use one leg of the 240 and neutral to get 120.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: Yet another auto transformer question.
    verdigo wrote: »
    I originally bought the PSX-240 when I thought I was going with an XW inverter. I found it on line for 399.00 with free shipping and I felt that was a good deal. I didn't wind up with the XW system but I am glad I got the PSX-240. It's really a handy piece of equipment. I have never understood why one would want to down convert 240 to 120 though since you can just use one leg of the 240 and neutral to get 120.

    Why would you buy an autotransformer if you were getting an XW which puts out 240 VAC split anyway?

    Because it can balance the 120 VAC outputs. Although the XW will allow a pretty big imbalance (70% if I recall correctly). This is often done with series stacked 120 VAC inverters providing 240 VAC and needing also to provide 120 VAC; keeps one inverter from having to shoulder most of the load.
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  • animatt
    animatt Solar Expert Posts: 295 ✭✭✭
    #8
    Re: Yet another auto transformer question.

    Chris used to talk about using an auto transformer on his xw6048 IF i remember correctly. I think inverter would hum alot if out of balance too much. I think not sure effeciency was better with the auto transfromer, even after its losses.(heavy loads) Although chris did push his equipment hard.

    I could be remembering wrong though.
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #9
    Re: Yet another auto transformer question.
    Cariboocoot wrote: »
    Why would you buy an autotransformer if you were getting an XW which puts out 240 VAC split anyway?

    Because it can balance the 120 VAC outputs. Although the XW will allow a pretty big imbalance (70% if I recall correctly). This is often done with series stacked 120 VAC inverters providing 240 VAC and needing also to provide 120 VAC; keeps one inverter from having to shoulder most of the load.

    At the time I was listening to Chris Olsen who stated that it was needed to balance loads.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: Yet another auto transformer question.
    verdigo wrote: »
    At the time I was listening to Chris Olsen who stated that it was needed to balance loads.

    Just one more thing he got wrong.
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