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Thread: intermittent pump cycling

  1. #1
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    Default intermittent pump cycling

    Hi,

    I have a deep well submersible pump with iron pipe with a 30/50 Square D pressure switch on
    a 13 year old Gould bladder tank. The problem occurs after the system reaches the cut out. A minute or
    two later the pump turns back on and runs for less than a minute. It cuts off, then repeats
    this behavior for three or four times. Then it seems all is well and working normal with regular cycling till
    it reaches the next cut out. It always occurs at the cut out. Suspecting (or hoping) the pressure switch was bad, I replaced it, but the same pattern continues. I have checked the toilets,
    but have not found any leaks. No water comes out of the bladder valve and it checks at 28 to 30 psi.
    Can someone explain what is going on and what needs fixed. Thanks

  2. #2
    Moderator valveman's Avatar
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    You have a bad check valve on the pump. Sometimes it hits right and seals and the next time it doesn't.

  3. #3
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    Thanks. I was afraid it was something like that or the pipe in the well leaking. Would it be worth
    the cost to have it pulled and fixed or just wait till the pump dies? The pump is probably 20 years old.
    Thanks again.

  4. #4
    Moderator valveman's Avatar
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    You can install anouther check valve up top. That is going to cause water hammer on pump start, but it will keep water from going backwards. With a 20 year old pump, you probably should just replace the pump when you have it out. Most pumps come with a built in check valve.

  5. #5
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by solafide View Post
    No water comes out of the bladder valve and it checks at 28 to 30 psi.
    No water from the bladder valve is inconclusive. A bladder could be 90% waterlogged and have a tiny bit of air at the top of it. If the valve is at the top of the tank, it has to be 100% waterlogged for water to come out of it. The best way to check it is to do drawdown tests.

    Adding a checkvalve topside is a stop-gap measure. If the water table is more than 30 feet below the surface, a vacuum will form and water hammer will result. Pulling the pump and adding a checkvalve to the bottom is the way to go. Now, if you have to pay someone to pull the pump, then you might as well replace it. You don't say how deep the pump is set.

  6. #6
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    Hi again and thanks for your replies. The system's behavior still seems confusing. There does not seem to be any leaks or pressure drops.
    It has a new 30/50 pressure switch as described above (but the symptoms are the same). When the pump comes on it fills the tank to only 42 psi or so. Then after a minute (with no pressure drop), the pump comes on again and runs a few seconds getting
    the pressure to 44 or 46. A few seconds or minute later (with no pressure drop) the pump comes on
    again and runs for a few seconds getting the pressure to 52. It came on a fourth time and got the pressure to 54.
    After reaching that point, all seems well and normal. (Sometimes it seems to take it three tries, other times four to
    finally be done). It is on a submersible pump around 150 feet deep.

  7. #7
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by solafide View Post
    When the pump comes on it fills the tank to only 42 psi or so. Then after a minute (with no pressure drop), the pump comes on again and runs a few seconds...
    The additional info you provided suggests that the pump may be going into thermal overload.

  8. #8
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by solafide View Post
    The problem occurs after the system reaches the cut out...
    Apparently it doesn't reach cut-out without... um... cutting out prematurely.

  9. #9
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    You need to check for under-voltage and/or over-current. Pump current draw generally follows GPM, meaning that more GPM = more current. As pressure increases, GPM and subsequently current draw normally decreases. This then does not manifest the symptoms you provided.

    Pump motor cooling requires that sufficient flow be maintained. As GPM reduces so too the cooling flow reduces. If the pump motor is buried in sediment it is more prone to thermal overload trips.

    A properly functioning thermal overload takes longer than a minute or two (what you describe your symptoms to be) to reset itself. My guess is the thermal overload (or your stopwatch) is not working properly. I think you need a good pump man to check out your system.

  10. #10
    Moderator valveman's Avatar
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    Some thermal overloads reset fairly quickly while others take a while. I think it has to do with the temperature of the water. There is no timer on the overloads, they just have to cool down to reset. So the cooler the water, the sooner they reset themselves. An amp meter will tell you for sure, but I am certain the overload is tripping.

  11. #11
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    Would reducing the cutoff to 40 psi help things? It's a 230 volt pump (not sure how many hp) and should normally be able to handle 50 I would think.

  12. #12
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    It might help for a short while to reduce the cutoff to 40 PSI. But the only thing that is going to fix the problem is a new motor.

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