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Thread: Well Pumps w/ Modified Sine Inverter

  1. #1
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    Default Well Pumps w/ Modified Sine Inverter

    I have heard the modified sine wave inverters do not start motors very well, but my 13 amp skill will start on my smaller 800/1600 watt inverter. Why will skill saws and vacuums run just fine but a well pump won't?

    I guess my real question is...

    What kind of submersible well pump can I get for mod. sine wave inverter (1250 watt/2500 watt)? The static level of the well in about 15' down and it's another 15' up to the house 1st floor...

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    Starting is not the main issue, it is running for extended period of time. Motors run hot with MSW which wears the windings in the motors out and synchronized AC motors will not work at all.
    MSEE, PE

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    Quote Originally Posted by Sunking View Post
    Starting is not the main issue, it is running for extended period of time. Motors run hot with MSW which wears the windings in the motors out and synchronized AC motors will not work at all.
    My situation is this:

    -I am building a spec house that will (most likely) eventually be hooked to the grid. The house is finished on the outside and sheetrock is painted on the inside and I am ready to start trimming windows and building kitchen counters/cabinets and installing interior doors.

    - Well has been drilled and piping between well & house is installed.

    - plumbing is roughed in.

    I would like to install a submersible pump Now that I can run on my solar PV system that will also be suitable for running from the grid.

    I guess I can have a dedicated pure-sine wave inverter for the submersible, but was wondering if there are pumps the will work with mod-sine wave?

    I think the run is too far to go with a 12 volt pump.

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    Many power tools have "brushed" " universal" AC/DC motors, and don't have starting capacitors. they don't care about sine/mod sine.

    Most AC well pumps have induction (AC only) motors, and starting capacitor, and run capacitor.

    If your water is only 15' down, you can use a surface pump, they can suck water to about 20' before they cavitate. And after the pump, it's easy to push the water up. But, that does not get you water pressure in your house, you need a pressure tank, or a 30' high tower to hold water.
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    Quote Originally Posted by Mike90250 View Post
    If your water is only 15' down, you can use a surface pump, .
    I am definitely going with a submersible. I would have to put a shallow well pump in the house (to protect from freezing) and that would be a lift of 30'.

    Also, I have already installed the pitless adapter and backfilled the 1" 160 PSI waterline and some 12-2 UF. The drilled well is 160 feet deep with 10 GPM, so I will be putting the pump down at least 100' below grade.

    this link is telling me I can use a mod. sine inverter with a 2K peak and 970 continuous watts to power a 0.5 HP submersible pump.

    http://www.wholesalesolar.com/Inform...rwellpump.html

    I think I might just get a 1/2 HP 115 VAC submersible and try it with my existing 1250/2500 watt mod-sine wave inverter.

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    Quote Originally Posted by Perry View Post

    this link is telling me I can use a mod. sine inverter with a 2K peak and 970 continuous watts to power a 0.5 HP submersible pump.

    http://www.wholesalesolar.com/Inform...rwellpump.html

    I think I might just get a 1/2 HP 115 VAC submersible and try it with my existing 1250/2500 watt mod-sine wave inverter.
    $0.05 says the pump inverter combo won't last a month.

    I'm running a 1/2 hp pump with 160' lift, 7gpm, and it pulls 1,002 w off my pure sine inverter @ 240VAC. (see .sig pump model) Mod sine will take 20% more power, so that's going to be 1200w cont, motor run 20% hotter, and a 2KW peak won't start a 1000w motor which needs 5-10x start power, over run power. My inverter has 12KW surge. I'm not sure wholesalesolar has reliable info posted in their table.

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    PS-
    I went with a conventional well pump, not the $2000 solar pump
    Last edited by Mike90250; 03-06-2011 at 02:23 PM. Reason: PS

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    Quote Originally Posted by Mike90250 View Post
    $0.05 says the pump inverter combo won't last a month.

    I'm running a 1/2 hp pump with 160' lift, 7gpm, and it pulls 1,002 w off my pure sine inverter @ 240VAC.
    PS-
    I went with a conventional well pump, not the $2000 solar pump
    Thanks for the info. I may have to rethink the idea. I really have no need for water right now as I still have lots of work on the spec house before someone is living there. It would just be nice to have the water hooked up so potential buyers could at least see the toilets flush.

    My total head is only 30 feet though so maybe I could get by with a smaller pump?

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    Quote Originally Posted by Perry View Post
    ....My total head is only 30 feet though so maybe I could get by with a smaller pump?
    You need to get with a competent plumber / well person.

    1) a surface mount pump can suck water up, about 20' max. You could hook one up to your well pipe, and if the static level does not drop too much, you could slowly pump (even 1 gpm is oodles of water) Just because your well is 100' deep, doesn't mean you have to put the pump way down there.

    2) surface mount pump can pump as high above the pump, as it's limits are, even while sucking from 15' below ground.

    3) you need some sort of storage container, pressure tank or something to limit the pump cycle time.

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    Quote Originally Posted by Mike90250 View Post
    You need to get with a competent plumber / well person.
    Thanks Mike, but as I will eventually be connected to the grid, I am resisting the temptation to use a suction pump. Submersibles seem to be the standard for deep well pumps in my area and the realtors tell me that buyers are often scared off by shallow well pumps. I will be using a standard pressure tank also. The only non-standard thing I am considering is using a 115 VAC submersible (instead of a 230 VAC) so I have the option of using a small generator for grid outages.

    So far I have done EVERYTHING on this house (except the foundation) including cutting the hole through the well casing and installing the pitless adapter. While I am not a competant plumber, I still have plumbed up three complete houses and a bunch of smaller jobs. I have installed several deep well pumps and yarded a few back up out of the well to get them repaired/replaced. I may not be fast, but I consider myself half-fast.

    Also, keep in mind that everyone in my town is running off a well since there is NO town water. In the old days everyone had springs or shallow wells but now-a-days, the perception is that shallow wells will run dry in times of drought but deep wells don't. People see those little pump houses and they see problems and they get scared off.

  10. #10

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    Just last week, I upgraded my inverter from a Trace 2500 w. 12. mod. sine wave to an Outback pure sine wave.

    That being said, the Trace has been in 24/7 use running our household for 20+ years. There has never been an issue with anything, appliances, motors, electronics, including computers.

    We have a Grunfos 120 v. soft-start well pump which provides our water, the head is about 100 ft. This is a 5 gpm model. The pump has been in operation for almost five years, no problem from the Trace mod sine wave inverter.

    [We upgraded to the Outback because we needed a more user-adjustable inverter for some new batteries we have on order, or the Trace would still be in use.]

    We only pump the well water during sunlight hours, the water going into a cistern from which we pump into the house with a Dankoff 12 v. Flowlite pump. So the Grunfos is not in round-the-clock use.

    But we have never had an issue with the mod. sine wave inverter. The only one we've used is the Trace, so I cannot speak to any others.

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