Auto-Transformer question.

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verdigo
verdigo Solar Expert Posts: 428 ✭✭
in Solar Beginners Corner #1
I finally have my inverter, a GVFX3648. Previously I had purchased a PSX-240. If I use it to bump up my voltage to 240 will it split the available 30 amps from the inverter to 15 amps total per leg? I am also wondering how much power it will consume.

Thanks

Dennis
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Auto-Transformer question.
    verdigo wrote: »
    I finally have my inverter, a GVFX3648. Previously I had purchased a PSX-240. If I use it to bump up my voltage to 240 will it split the available 30 amps from the inverter to 15 amps total per leg? I am also wondering how much power it will consume.

    Thanks

    Dennis

    Yes, but no: output Volt Amps remains the same so you have 15 Amps @ 240 Volts but because you are using an autotransformer either leg independently can still supply the full amount at 120 VAC.

    It will not consume a noticeable amount of power: they are better than 95% efficient if I recall correctly.
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #3
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    Re: Auto-Transformer question.

    Thanks. So if I understand correctly, there will be 30 amps for either leg as long as a total of 30 amps is not exceeded?
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #4
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    Re: Auto-Transformer question.
    verdigo wrote:
    Previously I had purchased a PSX-240. If I use it to bump up my voltage to 240 will it split the available 30 amps from the inverter to 15 amps total per leg?
    Cariboocoot wrote: »
    so you have 15 Amps @ 240 Volts but because you are using an autotransformer either leg independently can still supply the full amount at 120 VAC.

    Just to be slightly clearer: "Full amount" does not mean 30 amps on each leg. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: Auto-Transformer question.
    verdigo wrote: »
    Thanks. So if I understand correctly, there will be 30 amps for either leg as long as a total of 30 amps is not exceeded?

    Yes. Or more accurately so long as the 30 Amps from the inverter is not exceeded.

    BTW you shouldn't count on running any inverter at full power for any extended period. And 30 Amps @ 120 VAC is the max on a 3648.
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #6
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    Re: Auto-Transformer question.
    Cariboocoot wrote: »
    BTW you shouldn't count on running any inverter at full power for any extended period. And 30 Amps @ 120 VAC is the max on a 3648.

    Understood. I wouldn't have the battery for that anyway.

    Thanks
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  • H2SO4_guy
    H2SO4_guy Solar Expert Posts: 213 ✭✭✭
    #7
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    Re: Auto-Transformer question.

    My PSX-240 (From NAWS) draws about 10 watts, but quite a bit when you first turn it on. I shut mine off if I'm leaving for any amount of time as the mini split draws about 18 - 19 watts when off, so it saves 28-30 watts being off.

    Works great, but I don't push it hard, just to run the 9000 BTU mini split.
    12K asst panels charging through Midnite Classic 150's, powering Exeltechs and Outback VFX-3648 inverter at 12 and 48 volts.  2080 AH @ 48 VDC of Panasonic Stationary batteries (2 strings of 1040 AH each) purchased for slightly over scrap, installed August 2013.  Outback PSX-240X for 220 volt duties.  No genny usage since 2014. 
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #8
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    Re: Auto-Transformer question.
    H2SO4_guy wrote: »
    My PSX-240 (From NAWS) draws about 10 watts, but quite a bit when you first turn it on. I shut mine off if I'm leaving for any amount of time as the mini split draws about 18 - 19 watts when off, so it saves 28-30 watts being off.

    Works great, but I don't push it hard, just to run the 9000 BTU mini split.

    This one will be off most all the time as it will be for backup. Most of the time the system will just supplement the house in grid tied mode. I figure I will cycle the batteries and do an EQ once a month to maintain the batteries.
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  • H2SO4_guy
    H2SO4_guy Solar Expert Posts: 213 ✭✭✭
    #9
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    Re: Auto-Transformer question.

    That is a reasonable choice and it will make your genny much happier by not loading only one side of the windings. It can get ugly otherwise and shorten the life due to being unbalanced. I was going to buy another one for charging batteries, but when we have a lack of sunlight, I just reduce loads and haven't used a genny in over a year. I do lots of stuff that most wouldn't with batteries. How many heat their living area with batteries? I use a $1300 battery pack (used) and it powers the air source heat pump. I have had the batteries 9 months now and ran AC all last summer and heat all winter. It works for me, but I do keep an eye on things so as to not take them down too far.

    Good luck and let us know how it works out,

    Skip
    12K asst panels charging through Midnite Classic 150's, powering Exeltechs and Outback VFX-3648 inverter at 12 and 48 volts.  2080 AH @ 48 VDC of Panasonic Stationary batteries (2 strings of 1040 AH each) purchased for slightly over scrap, installed August 2013.  Outback PSX-240X for 220 volt duties.  No genny usage since 2014. 
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #10
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    Another auto-transformer question

    In my shed where my power equipment is located I have a breaker box that will ultimately connected to the house panel via a manual transfer switch. I have connected a PSX-240 auto transformer wired to deliver 240 volts to the shed breaker box. The question is does the auto transformer need a neutral/ground bond to operate?

    Thanks

    Dennis
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #11
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    Re: Auto-Transformer question.

    Wow. I don't think I have as much ambition as you "looking at your signature line". I am having fun though.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #12
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    Re: Another auto-transformer question

    Would be good to keep it all in one thread, so folks don't have to go searching back and forth on basically the same topic.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #13
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    Re: Another auto-transformer question

    Outback has some good manuals on their Autotransformer:

    http://www.outbackpower.com/downloads/documents/autotransformer/manual.pdf

    Are you looking for 240 VAC only at the shed?

    Or 120/240 VAC split phase power?

    Grounded neutrals are for safety--Not for operational reasons (for most appliances).

    A few things such as florescent tube fixtures, some spark ignition systems for gas flames (stove/water heater/etc.), and such may not operate correctly without a ground bonded neutral.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #14
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    Re: Another auto-transformer question
    waynefromnscanada wrote: »
    Would be good to keep it all in one thread, so folks don't have to go searching back and forth on basically the same topic.

    Actually two different topics on the same piece of equipment but hey I don't have a problem with moving it.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #15
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    Re: Another auto-transformer question

    Here's a novel idea; let's try answering the question! :D
    verdigo wrote: »
    In my shed where my power equipment is located I have a breaker box that will ultimately connected to the house panel via a manual transfer switch. I have connected a PSX-240 auto transformer wired to deliver 240 volts to the shed breaker box. The question is does the auto transformer need a neutral/ground bond to operate?

    Thanks

    Dennis

    This is a trick question, in fact. Why? Because in order to get 240 VAC out of the PSX-240 you have to put 120 VAC in. And where you do that you will have a hot wire and a neutral wire that is already bonded to ground. That neutral connects to what is effectively the center tap of the transformer; the two white wires in this case. You then get a mirror image of the output waveform on the other windings, giving you 240 VAC between the 'input' hot (L1, black wire) and the 'output' hot (L2, red wire) as well as 120 VAC between the neutral and either L1 or L2. This is normal power standard her in North America.

    You would not, for example, connect up the inverter to the transformer without the neutral-ground bond on the input and then bond L2 on the output.
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #16
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    Re: Another auto-transformer question

    Well... It wasn't working, so I bonded the the neutral and ground with the green screw. Still didn't work. I found the A/C hot out breaker tripped tn the "inverter bypass interlocked pair" on the e-panel. Do you think attempting to operate the auto transformer without the neutral ground bond tripped it?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #17
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    Re: Another auto-transformer question
    verdigo wrote: »
    Well... It wasn't working, so I bonded the the neutral and ground with the green screw. Still didn't work. I found the A/C hot out breaker tripped tn the "inverter bypass interlocked pair" on the e-panel. Do you think attempting to operate the auto transformer without the neutral ground bond tripped it?

    I'm going to guess you had a load attached to the 240 VAC output. Yes? Worst case: a motor.
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #18
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    Re: Another auto-transformer question

    A heat lamp because it was handy, but it was on a 120 circuit after the PSX-240. Its all working now.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #19
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    Re: Another auto-transformer question
    verdigo wrote: »
    A heat lamp because it was handy, but it was on a 120 circuit after the PSX-240. Its all working now.

    In other words connected L2 to neutral?
    As you suspect, without the ground reference for the 120 VAC neutral point the actual Voltages can go up/down out of range as the transformer 'feeds back on itself' creating untold havoc. A motor can actually generate Voltage due to residual magnetism and back-feed to the inverter. That can be bad enough to blow the inverter.
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #20
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    Re: Another auto-transformer question

    I'm not sure I am following. I hooked up the inverter according to this link's step up configuration diagram http://www.outbackpower.com/downloads/documents/autotransformer/manual.pdf. The 240 volt out legs I connected to a regular 240 volt breaker back feeding L1, and L2 of a breaker box. I also grounded the PSX-240 to the breaker box's ground bus. I just didn't install the neutral/ground bond screw that came with the breaker box. I wired in a standard 120 volt receptacle and plugged the light into that.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #21
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    Re: Another auto-transformer question

    Can you tell me which diagram you followed in that document? Because I've just read through the whole thing twice and there is none that shows how to wire a PSX-240 to the output of a single FX inverter to get 240 Volts from it.

    Ever since Outback's last web site upgrade it's practically impossible to find anything. It used to be very good. Not anymore. :p
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #22
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    Re: Another auto-transformer question

    Its the one on page 5. "Step Up Transformer Configuration" Just using the Inverter as the 120 volt source. Sorry. Wrong link. Try this one. http://lib.store.yahoo.net/lib/wind-sun/PSX-240-manual.pdf
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #23
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    Re: Another auto-transformer question
    verdigo wrote: »
    Its the one on page 5. "Step Up Transformer Configuration" Just using the Inverter as the 120 volt source.

    That's close. The difference being feeding in to two FX's operating as a single unit; i.e. a matched load on each leg of the 240 Volts. Without that load matching you really need the grounded neutral or else the unbalanced legs can be wildly unbalanced.

    Anyway you've got it working now, and that's good. :D
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #24
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    Re: Another auto-transformer question

    I gave you the wrong link. This is the manual I used. http://lib.store.yahoo.net/lib/wind-sun/PSX-240-manual.pdf Page 5 Sorry for the mix up.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #25
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    Re: Another auto-transformer question

    I'll take your word for it as I can't even get that one to load.

    Don't you just love it when they 'improve' web sites so that they no longer function? That makes them better, does it? Well perhaps it does at that. :roll:
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #26
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    Re: Another auto-transformer question
    Cariboocoot wrote: »
    I'll take your word for it as I can't even get that one to load.

    Loading for me Coot, but was EXTREMELY slow doing so. So slow I don't have the patience to wait. Been 5 minutes now and still only part loaded.
    Don't know if it's my connection to wherever the info is coming from, or if the source is on dialup. lol
    Did finally load the complete 10 pages, some of which had little or no info on them.
    In the 3 different wiring diagrams, in each case wire (or terminal) #2 and #3 are connected together and go to Neutral, regardless if the transformer is wired for step-up, step-down, (or step sidewise :D )
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #27
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    Re: Another auto-transformer question

    8)The last link is from the NAWS catalog. But it is working as advertised. Gave me a thrill up my leg8)
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #28
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    Re: Another auto-transformer question

    The site probably just hates Canadians. :p:D
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #29
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    Re: Another auto-transformer question
    Cariboocoot wrote: »
    The site probably just hates Canadians. :p:D

    The benefits of Free trade. :D
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #30
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    Re: Another auto-transformer question

    Just found this link to a more descriptive owners manual for the transformer:
    http://lib.store.yahoo.net/lib/wind-sun/FW-X240-manual.pdf
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  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    #31
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    Re: Another auto-transformer question

    Just noticed that my lights came on without the autotransformer being switched on. So I switched it on, it started humming, no change. Switched it off no hum, and the lights remain on. This is the PSX-240 that comes with two 25 amp circuit breakers, and a cooling fan. Switching it on or off is being done with the breakers.
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