step-up transformer basics

elesaverelesaver Solar Expert Posts: 185 ✭✭
I'm still researching the use of a transformer to step up from 120VAC to 240VAC for powering a well pump. The pump specs: 1/2 hp, 0.073KW, maximum amps 6.0-7.5. I have an outback VFX3524 inverter with a 480 aH 24V battery bank. I know there is an Outback transformer that can be used but I'm wondering if that is overkill for this application? I have seen MANY transformers available but it is unclear what is really required and/or can these transformers be easily wired with inverter. I'd love some help to sort out the info. A $500 transformer may not be required.
1st system:  24Vsystem with 8 X 300W panels, Midnite Solar combiner box, Midnite Solar mini-dc disconnect, Midnite Solar Classic 150, Outback VFX 3524 with mate, 2 X 12V  fforklift batteries in series 938 aH,  (Outback PSX transformer, Honda EU3000is...not currently hooked up but available if/when needed)

2nd system:  24V system with 4 X 310W panels, Midnite Solar combiner box, Midnite Solar mini-dc disconnect, Midnite Solar Classic 200, Cotek 1500W pure sine inverter, Trojan 125 batteries (8 available but "currently" using 4)

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: step-up transformer basics

    I know what you mean: a 4kVA transformer is sort of overkill for running one pump that's going to draw less than 1kW.

    First off, what exactly is the pump? Deep well or surface type? Some of them will run either 120 or 240 depending on how you make the connection so perhaps you can switch the wiring around. That would be the simple answer, if it is possible.

    Also if we look at some of the numbers you've supplied there's a few puzzles. 1/2 HP is 373 Watts, definitely not 0.073 kW (73 Watts). But the HP rating doesn't mean much to the power consumption of a pump. 730 Watts running I can believe. Then there's the current draw: 6.0 to 7.5 Amps? On 240 VAC? That's 1440 to 1800 Watts. That is the start-up demand my 3/4 HP deep well pump has: running it draws 3 Amps. Can you check these specifications?

    Otherwise you're looking for an autotransformer than can handle the start-up power demand of the pump, whatever it may be.
  • stmarstmar Solar Expert Posts: 330 ✭✭✭
    Re: step-up transformer basics

    I have a Trace T-220 that can run a 1-1/2 hp submersible well pump and it has 15 amp resets/breakers. Unfortunately they don't make this product anymore and that is why I am using the grid for my pump and saving my T-220 for emergencies. I used the T-220 for many years (15) before I retired it and it was still functioning properly.
  • elesaverelesaver Solar Expert Posts: 185 ✭✭
    Re: step-up transformer basics

    Thanks for the info so far. The numbers that I provided were given to me by the plumber who installed the pump so I have no way of knowing. In fact, it took him 3 weeks and 5 phone calls to respond with this info. He will not be called upon for anymore plumbing work here, as you can imagine. But, I digress.

    The pump is a submersible, Red Jacket pump. The well depth is approx 100 ft. I was told this one will not run on 120 VAC. When I asked, I was told that those pumps are not submersible, so perhaps he really doesn't know much.

    Perhaps I recorded .073kw when it should've been 0.73kw? I was writing the info quickly so I could've made an error there. The breaker in the service panel for the pump is a 30 amp but I have recorded that he said a 15 amp breaker. The MAXIMUM amps (he did say maxiumum) was 6.0-7.5. I do not understand why there would be a maximum amp range given. I have tried to research this kind of pump but didn't come up with much that I understood.

    So, that's the best I can come up with. There would not be a big demand for the pump actually. I would only run it during the times there is no electricity and then, only to re-pressurize the holding tank to flush but not to use a dishwasher or anything like that. I live in an area (SE US) where we have ice storms and the power is frequently off...sometimes as long a 5 days. I'm trying to be able to survive during those times as well as trying to learn to enjoy some solar power production along the way to save a bit on the power bill.

    Any additional help is always appreciated. Perhaps with the scant info I know, I'm beyond help?
    1st system:  24Vsystem with 8 X 300W panels, Midnite Solar combiner box, Midnite Solar mini-dc disconnect, Midnite Solar Classic 150, Outback VFX 3524 with mate, 2 X 12V  fforklift batteries in series 938 aH,  (Outback PSX transformer, Honda EU3000is...not currently hooked up but available if/when needed)

    2nd system:  24V system with 4 X 310W panels, Midnite Solar combiner box, Midnite Solar mini-dc disconnect, Midnite Solar Classic 200, Cotek 1500W pure sine inverter, Trojan 125 batteries (8 available but "currently" using 4)

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: step-up transformer basics

    Well it looks like we have to go on a bit of speculation.

    First bit: 100 foot deep well is going to have a submersible 240 VAC pump in it. Definitely not a 120 VAC unit. 6-7.5 Amps would be normal start-up for that. There is always some range because pumps can be used at various depths with different static head and such which changes the amount of resistance the motor encounters when it tries to start. I have no idea why there would be a 30 Amp breaker on it as 15 Amps would be adequate (probably runs 10 AWG wire considering the distance involved).

    As such you are looking at the need for nearly 2kW for starting, which is not surprising. So in theory you could use a 2 kVA autotransformer, but if you can find such is it going to be significantly cheaper than the 4 kVA unit?

    There is always the option of the clunky 240 VAC gas gen on an as-needed basis. Also helps to have a large capacity pressure tank so that pump cycles are minimal.
  • elesaverelesaver Solar Expert Posts: 185 ✭✭
    Re: step-up transformer basics

    OK. Yes, I understand. I have to keep mulling this stuff over. My skull density is greater than most. :-) If I ever get a generator, I am considering a propane generator with an electric start. I've seen those that have the propane cylinder like a gas grill uses. Multiple uses then. I still have to do some research on that and it won't be anything to purchase too soon.

    Thanks for the help. It may be wise to go with the outback psx 240 just in case anyway. At least I'd know it would work with an outback inverter!
    1st system:  24Vsystem with 8 X 300W panels, Midnite Solar combiner box, Midnite Solar mini-dc disconnect, Midnite Solar Classic 150, Outback VFX 3524 with mate, 2 X 12V  fforklift batteries in series 938 aH,  (Outback PSX transformer, Honda EU3000is...not currently hooked up but available if/when needed)

    2nd system:  24V system with 4 X 310W panels, Midnite Solar combiner box, Midnite Solar mini-dc disconnect, Midnite Solar Classic 200, Cotek 1500W pure sine inverter, Trojan 125 batteries (8 available but "currently" using 4)

  • stmarstmar Solar Expert Posts: 330 ✭✭✭
    Re: step-up transformer basics

    That PSX looks like a good unit, I was surprised that the choices were so limited, unless I am not searching correctly. You have a multitude of generator choices, some have the propane conversion kit available and there are even some that come with multi-fuel options. A friend of mine just got the Duromax 4400 watt dual fuel, it looks like a good unit and was about half of what I paid for my gas powered Honda. A few months ago another poster had a thread about the Duromax so you can do a search and see what his experience is so far with it.
  • elesaverelesaver Solar Expert Posts: 185 ✭✭
    Re: step-up transformer basics
    stmar wrote: »
    That PSX looks like a good unit, I was surprised that the choices were so limited, unless I am not searching correctly. You have a multitude of generator choices, some have the propane conversion kit available and there are even some that come with multi-fuel options. A friend of mine just got the Duromax 4400 watt dual fuel, it looks like a good unit and was about half of what I paid for my gas powered Honda. A few months ago another poster had a thread about the Duromax so you can do a search and see what his experience is so far with it.

    Thanks, stmar. Sounds like a good research project for sure. I'll get right on it.
    1st system:  24Vsystem with 8 X 300W panels, Midnite Solar combiner box, Midnite Solar mini-dc disconnect, Midnite Solar Classic 150, Outback VFX 3524 with mate, 2 X 12V  fforklift batteries in series 938 aH,  (Outback PSX transformer, Honda EU3000is...not currently hooked up but available if/when needed)

    2nd system:  24V system with 4 X 310W panels, Midnite Solar combiner box, Midnite Solar mini-dc disconnect, Midnite Solar Classic 200, Cotek 1500W pure sine inverter, Trojan 125 batteries (8 available but "currently" using 4)

  • jtdiesel65jtdiesel65 Solar Expert Posts: 140 ✭✭✭
    Re: step-up transformer basics

    I used a transformer for years to do this. It was wired in at the pressure switch. This was off grid with a 120v inverter. The problem with transformers is inrush current.

    I wondering how everything is going to be wired. Maybe it's easier to get a split phase inverter.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: step-up transformer basics
    jtdiesel65 wrote: »
    I used a transformer for years to do this. It was wired in at the pressure switch. This was off grid with a 120v inverter. The problem with transformers is inrush current.

    I wondering how everything is going to be wired. Maybe it's easier to get a split phase inverter.

    Easier perhaps, but not cheaper when you've already got an inverter.
  • jtdiesel65jtdiesel65 Solar Expert Posts: 140 ✭✭✭
    Re: step-up transformer basics
    Easier perhaps, but not cheaper when you've already got an inverter.

    Oh, I know.

    IIRC some of those 120v Grundfos soft start pumps will work past 100ft.

    googling...

    http://www.enviroharvest.ca/grundfos_sq.htm
    http://www.newenglandsolar.com/pdf/Pumps,%20Water.pdf
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