Shallow well pump low pressure cut off question

Discussion in 'Pumps and Wells' started by Hank Doink, May 13, 2018.

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  1. May 13, 2018 #1

    Hank Doink

    Hank Doink

    Hank Doink

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    In a nutshell, I recently damaged my shallow well pump by mistakenly running it dry. I was having my cistern cleaned and sealed so we were temporarily drawing water from 55 gallon drums. Needless to say while losing track of the water level in the 55 gallon drum it ran dry. My wife told me "the pump won't shut off " my eyes got big and I realized I should have moved the foot valve to the full drum. So now the pump won't create enough pressure to break the pressure switch. It rises to 42# and thats it.
    My question is why didn't the low water cut off shut the pump off?
    Its supposed to shut it off 10# below the cut in pressure.
    I'm somewhat familiar with centrifugal pumps, been doing HVAC work for 30 years. I'm not so familiar with the shallow well pump. The pressure switch is looking at the discharge of the pump or the pressure in the plumbing feeding the house, so it seems that the pressure stayed just above the cutout point long enough to damage the pump. When I shut it off, the pump housing was smoking hot, probably close to making steam!
    The Square-D switch I have is a 9013FSG 2M4U2.
    Wondering if this is a common occurrence. I've exercised the switch over the years, I know it does shut off when pressure gets low. Seems the foot valve did its job, the pump was trying to raise the pressure but unless a faucet was open the pressure was such that the pump kept running until it was damaged? Seems there should be a better way to protect the pump?
     
  2. May 14, 2018 #2

    Valveman

    Valveman

    Valveman

    Pump Controls Tech Professional

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    There is a better way. Low pressure cut off switches only work when you have a faucet open. If it pumps the source dry while trying to fill the pressure tank, the pressure doesn't go low enough to shut the pump off. A device like the following that looks at motor amps works no matter if a faucet is open or not.
     

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