current sensor for well pump

Discussion in 'Pumps and Tanks Well Forum & Blog' started by Thatguy, Nov 12, 2010.

  1. Thatguy

    Thatguy Homeowner

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    that stops the pump if the current draw is too high or too low.

    Is there any reason not to have one?
  2. valveman

    valveman Moderator Staff Member

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    Your motor and/or the control box will already have an overload. No need to be redundant on overloads. An underload device is a good idea if you have a well that cold be pumped dry.
  3. Texas Wellman

    Texas Wellman In the Trades

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    You could probably achieve the same result with an M4 (debatable), but after about the 5th reset you would be ready to rip it out. Your low-current trip is only treating the symptom, not the problem. They should only be used in an area where you cannot get enough volume out of the well and there is a danger of running a submersible pump dry. Never seen one mounted on a jet-pump setup, but then again, anything around here that makes less than 10 GPM is considered a dry hole. And that's for a 2" well.
  4. Thatguy

    Thatguy Homeowner

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    My take on it was that it was preventing pump/motor damage and my impression was that pumps run dry frequently. If the cost is reasonable it sounds like a good idea. It's like paying a one time premium on "pump insurance".

    Somewhere I saw that less than 5 GPM is considered a "low yield" well even though 100 gals per person per 24 hour day is only 0.003 GPM per person per day.
    Last edited: Nov 14, 2010
  5. ballvalve

    ballvalve General Engineering Contractor

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    Its called a Franklin pumpsaver or a few other things, 150 bucks all over the country and internet. Adjustable current sensing.

    valveman also sells his own flavor of that device.

    Using low pressure cut out pressure switches also saves millions of pumps essentially for free or a few bucks more than a normal switch.
    Last edited: Nov 14, 2010
  6. Texas Wellman

    Texas Wellman In the Trades

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    Problem with that M4 Switch is that you can get caught between the 20 psi-cut out and the 30-psi cut in and the pump will still run dry, but they do seem to do what they were designed for.
  7. justwater

    justwater Well Drilling/Service

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    i dont really feel the need for protection on a jet pump. i guess if you are really itching for a something to do and wanna spend some money. regardless of some other opinions, a descent jet pump rarely runs dry long enough to ruin anything inside. i think i may have seen 1-2 ruin from heat, and it was a situation like a pump at a lakehouse ran dry for... ?? just like everyone else does, you'll notice when something isnt right.. fix the warped fittings on the pump and let it rock again.

    i have a barely visible scar on the inside of my arm that i got when i was 16-17 years old. went on a service call where a pump got a suction leak and had run dry for a while i suppose. when i took out the warped suction fitting, somehow i managed to get some of the water from the pump on my arm and it scalded me pretty bad. thats how hot it was. i called my dad crying and he told me to put some pvc cleaner (his cure-all) on it, pay better attention, and not to come home until it was fixed. lol.. ahole.. so i fixed the warped fittings, primed it and it ran like a top again. ive worked on truckload of descent quality jet pumps that ran hot, and rarely ever seen one ruin from it.

    yall might like this one. my first water well battlescar was when i was about 5 years old. i went with my dad and his helper to drill a well, of course i didnt help any. i was running around playing with a 1.25" galvanized coupling. for some reason i threw it up in the air as hard as i could and it came right back down on my head.. it was ugly. should have had stitches. i ran over to them bleeding and crying hysterically. when dad finally looked at me (because the helper noticed me and freaked out), he stopped the rig for about 20 seconds, sat me on a bucket and made me hold a rag on it until they finished the well. lol... ahole. that scar is still very visible. have to explain it any time someone new cuts my hair.
    Last edited: Nov 14, 2010
  8. ballvalve

    ballvalve General Engineering Contractor

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    I keep hearing that but it seems to not make sense, or to ever happen. If your caught between 20 and 30 psi, eventually it must fall to zero, no? a dry running pump will put zero on the switch and it will still trip to off.
  9. ballvalve

    ballvalve General Engineering Contractor

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    Justwater: dont really feel the need for protection on a jet pump. i guess if you are really itching for a something to do and wanna spend some money. regardless of some other opinions, a descent jet pump rarely runs dry long enough to ruin anything inside.

    I would guess that is because most if not all jet pump motors have heat switches built in "thermally protected" that reduce the dry run time. Indeed if this continues, the impeller melts or the seal cooks anyway.

    A low pressure cut out seems to save pumps 99% of the time for a few bucks cost.

    If the heat switch on a jet pump was on the face of the motor instead of the rear, they would never burn out dry.

    You can buy add on thermal switches, but no one seems to bother.
  10. justwater

    justwater Well Drilling/Service

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    i've never cared for low pressure cut outs. always seemed they were more of a pain than a help. maybe thats just me though. what do they save the pump from 99% of time? am i the only well guy in the world that doesnt have much trouble at all with insides of jet pumps ruining? who are these people that go without water for as long as it takes a pump to do this before they get it looked at? id love to get those jobs. when im checking to see if a pump "is any good", my only real concern is if the motor runs. i've never thought to myself "i wonder if its ran dry and the insides have melted". i would almost say 99% of quality pump replacements are because the motor burnt up from cycling, and usually from "short-cycling". those safety gadgets dont help much there. come up with a device that lets you know when your tank is waterlogged and you'll have something really useful.
  11. Texas Wellman

    Texas Wellman In the Trades

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    If the pump kicks on at 30 but you quit using water and something happens to the pump (loses prime, impeller breaks, etc) it can stay above 20 but below 30 so your pump runs. Actually most of the time the pump will not run "dry" but the heat still builds up if it can't build pressure.

    I'm with justwater. Rarely have I seen the insides of a quality jet pump destroyed by heat. The plastic on those insides is a high quality and usually can take more heat than you think.
  12. justwater

    justwater Well Drilling/Service

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    agreed, many things cause a pump to build heat and cause problems. run dry is a bad term i guess.. it runs hot rather. broke impeller/suction leak/plugged nozzle/switch problems/excessive cycling/etc. for whatever reason, a water pump that is running without moving water is heating up.
  13. ballvalve

    ballvalve General Engineering Contractor

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    Yes, a dry jet pump will probably just wear the seal down faster. A jet pump churning water and not moving it out will make steam.

    I am thinking more about submersibles for the issue of low pressure cut outs. Run that dry for a bit and you have big time wear on the bearings. The low pressure switch tells you instantly when you pulled the water below the inlet, and no matter the inconveniece, its saves a pull and a pump. I cannot find a scenario of switching where the low pressure cut out will NOT shut off the pump when the water is drawn off.

    If you leave the house at 8am and the hose is left on, or a pipe breaks, you will return at 6pm likely without a submersible unless you have a pumpsaver or pressure cutout or a high production well. Thermal switches in submersibles are good for overload due to poor design sizing causing amp draw overload, but not so much for a dry run.
    Last edited: Nov 14, 2010
  14. Thatguy

    Thatguy Homeowner

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    With my head cut my father gave me busfare to the hospital in the next town. I never did manage to "pay him back" for that one.
  15. valveman

    valveman Moderator Staff Member

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    A "Cycle Sensor" does that. And also looks for a dry well. The M4 works good to catch a main line break, and will catch a dry well most of the time. However, like wellmall said, the M4 sometimes will not catch a dry well when you have turned off the faucets just as the well is pumping dry. Then the well pumps dry while you are trying to fill the pressure tank. Since no one is using water at that time, the pressure does not drop so the M4 can shut off the pump. It just hovers at 20-30 PSI unitl the water gets hot and melts the pump and/or the inlet plumbing.
  16. justwater

    justwater Well Drilling/Service

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    Guess i need to pay better attention to things.. I'll have to take a look at the cycle sensors.
  17. ballvalve

    ballvalve General Engineering Contractor

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    The franklin boxes also sense frequent starts and shut down the pump, thus the device to sense a waterlogged tank is out there, granted for a price.

    I am going to guess that the chances [odds] of the low pressure cut out getting stuck in the on position are about the same as a electronic malfunction in the other sensors.

    Maybe thatguy can run a statistical probability on that thought.
  18. Gary Slusser

    Gary Slusser That's all folks!

    Over 18 yrs I probably replaced 1-4 jet pumps every yr due to overheating and melting things. Most were running for hours with suction leaks or a 'dry' well because the lady of the house didn't know to turn the power off when she found she didn't have any water. Short cycling for days or weeks due to a leaking foot valve is another cause.

    Myself, I wanted to know the condition of the pump as to how it developed pressure and the volume of water it delivered. I knew the motor ran because all I had to do was turn the power on when I arrived after telling the customer to turn it off when she or hubby called me to go out to fix things.

    I've never seen a low pressure safety cut off switch hang up.

    I didn't have collapsed PVC because it wasn't used, the pumps had PE pipe or galvanized with a very few having a few feet of copper over to the PE or galvanized going out to the well, pit or the occasional spring house.
  19. Thatguy

    Thatguy Homeowner

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    If a pump costs $500 and there is a 10% chance of a ruinous failure over the life of the well then you should spend less than 10% of $500 = less than $50 on the failure prevention device.
    For a 50% chance you should spend $250 or less.

    1 to 4 pump failures per year out of how many pumps "out there" that didn't fail each year?

    How long is the life of a well?
  20. justwater

    justwater Well Drilling/Service

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    Location:
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    Over the last 10 years, I probably service/replace 2-10 jet pumps per week. Ive seen insides melted very few times. I asked my dad (25 years exp.) this morning, he said the same thing, he's seen it but very rare. same type of deals here with the lady of the house, etc. Had one bout 2 weeks ago that had ran so long I had to cut the sch. 40 pvc back 5 feet or more before I could glue to it. fixed it and it made 60psi effortlessly.. It was a 3/4 starite btw, about the same age as OP's. Idk though, maybe the people in these woods are just a little quicker to catch things than some in other places of the country.

    I have a couple used heads and parts, maybe used motor or two, laying around here I don't care about. maybe i should do a test soon and we can all have a better idea just how long it takes to melt stuff. .. maybe one test pump plugged and full of water, and one partially full like when the suction leak happens after running hot.

    might be something cool to know one day... lol, had them for a while now but I'd probably need one of melted parts as soon as I did this.

    Btw thatguy, the life of a well has many variables. A better question might be what is the life of a particular type of well. A PVC well drilled correctly here should be the last well you ever need, as our wells don't require screens, are grouted in cement, and have open holes drilled into usually rock. steel cased wells seem to last around ten years here before they rust out. Then you have to consider other places where wells do require screens, and whatever other types of wells are out there which i am not familiar with. Porky might have a guestemate as to the average life of a well, it seems he's about done them all. my thought would be anywhere from a year or so up until the length it takes PVC to go away, which I was always told was never.
    Last edited: Nov 15, 2010
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