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  • A/C Water Pump

    I want to run a submersible A/C single phase 1 hp 110 volt pump motor. I have a 2400 watt 12 volt true sine wave Xantrex inverter. I have what I believe is enough battery power with six 6 volt 100ah AGM batteries providing 12 volts to the inverter (so about 300ah total at 12 volts). (3 banks of 2 batteries each in series) The problem is the inrush of the inductive load from the motor. I've been told the inrush current can be as high as 6 to 8 times the rated power of the motor. Since the motor draw is about 740 watts, the inrush could be as high as 5920 watts, way above the peak output capacity of the inverter. I've also been told that true sine wave inverters have a lot of trouble on the 1st few cycles trying to match power output required possibly damaging the inverter. I'm thinking of using a single phase soft start motor controller. My concern with this is, because the pump is submerged in a well 110 feet down, the soft start won't be able to get the motor turning with that load on it.

    An industrial electrician friend of mine was telling me that you can use a standard light dimmer switch that can handle the current to test the motor by turning up the dimmer and seeing if the pump starts properly. Does anyone have any experience with well pumps and soft start motor controllers? If so, any brand they can recommend?

  • #2
    Do yourself a favor. If you have an external capacitor box on a conventional centrifugal submersible pump look into a Franklin Electric monodrive. It converts the existing pump in the well to a soft start variable speed drive and does away with your surge loads. The drive replaces the external capacitor box. Not sure if you have any other options if you do not have an external capacitor as the monodrive needs access to the start winding of the motor which is only external if you have an external capacitor. Note if you dont have an external capacitor do yourself a favor and swap out the pump on a scheduled basis as at some point when you least expect it the capacitor down in the hole will fail at the worst possible time. It can die of old age or during a lighting strike.

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    • #3
      I cannot believe an electrician would suggest using a lamp dimmer to test a motor with.
      The inductive kickback would likely destroy the dimmer in an instant. Most say Incandescent lamps only
      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

      solar: http://tinyurl.com/LMR-Solar
      gen: http://tinyurl.com/LMR-Lister

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      • #4
        The Franklin Electric Monodrive looks good, but pricey. Could likely upgrade the inverter to handle the load for that price. I think one phase soft start is < $300 usd.

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        • #5


          1300 watts + surge watts light dimmer. Hummm!!!
          Last edited by Paul Land; 03-06-2019, 08:50 PM.

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          • #6
            From what I'm reading it might actually work! An electronic light dimmer is virtually the same circuit as a single phase soft start motor controller. They both use SCR's to chop the waveform. A 1 HP motor should draw 746 watts so a 1000 watt dimmer should work. As far as the inrush, that's what the SCR limits and that's how the soft start actually works to limit the inrush (on single phase, not 3 phase, that's when you have to vary the frequency and not the amplitude normally with a VFD) I have another old 1hp single phase motor I can try it on 1st. I will have the fire extinguisher handy!

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            • #7
              Originally posted by randyb128 View Post
              From what I'm reading it might actually work! An electronic light dimmer is virtually the same circuit as a single phase soft start motor controller. They both use SCR's to chop the waveform. A 1 HP motor should draw 746 watts so a 1000 watt dimmer should work. As far as the inrush, that's what the SCR limits and that's how the soft start actually works to limit the inrush (on single phase, not 3 phase, that's when you have to vary the frequency and not the amplitude normally with a VFD) I have another old 1hp single phase motor I can try it on 1st. I will have the fire extinguisher handy!
              I have this SCR on my electronics test bench I use it as a variable volt supply + 1:1 Isolation transformer $50 to separate voltage from circuit
              reg.png
              Last edited by Paul Land; 03-07-2019, 02:08 PM.

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              • #8
                Perfect. I bet that would work. Very inexpensive too.

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                • #9
                  Originally posted by randyb128 View Post
                  Perfect. I bet that would work. Very inexpensive too.
                  This is transformer I use its 120v:120v but I step it up to my needs on bench and use dimmer to run test volts starting with 45v-75v up to full volts . with dimmer i use dim bulb it must be incandescent to make dimmer work its wired in "series". I would use 120v:140v to cover volt drop from dimmer that should work.
                  jam.png
                  Last edited by Paul Land; 03-07-2019, 05:15 PM.

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                  • #10
                    You guys are making me nervous with this stuff. Let's stop with the half-assed lamp dimmer motor control suggestions.

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                    • #11
                      Originally posted by randyb128 View Post
                      From what I'm reading it might actually work! An electronic light dimmer is virtually the same circuit as a single phase soft start motor controller. They both use SCR's to chop the waveform. A 1 HP motor should draw 746 watts so a 1000 watt dimmer should work. As far as the inrush, that's what the SCR limits and that's how the soft start actually works to limit the inrush (on single phase, not 3 phase, that's when you have to vary the frequency and not the amplitude normally with a VFD) I have another old 1hp single phase motor I can try it on 1st. I will have the fire extinguisher handy!
                      If you are really lucky, it will merely silently fry the dimmer.

                      746 watts = 1 hp A "real" electric motor consumes much more when you consider power factor and other losses.

                      But keep on believing what Paul says, since he is showing the worse side of Greenwashing - False Hope

                      Last edited by Mike90250; 03-07-2019, 06:33 PM.
                      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                      solar: http://tinyurl.com/LMR-Solar
                      gen: http://tinyurl.com/LMR-Lister

                      Comment


                      • #12
                        Originally posted by Paul Land View Post

                        This is transformer I use its 120v:120v but I step it up to my needs on bench and use dimmer to run test volts starting with 45v-75v up to full volts . with dimmer i use dim bulb it must be incandescent to make dimmer work its wired in "series". I would use 120v:140v to cover volt drop from dimmer that should work.
                        jam.png
                        Congratulations on being banned for doing EXACTLY what we asked you not do (give incompetent technical advice to neophytes)

                        ANY OTHER Fraudsters/Shills/Peddelers and Ignoramus giving dangerous advice, will meet the same.
                        Last edited by Mike90250; 03-07-2019, 06:32 PM.
                        Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                        solar: http://tinyurl.com/LMR-Solar
                        gen: http://tinyurl.com/LMR-Lister

                        Comment

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