Pressure Switch Chatter & Check Valve location

Discussion in 'Pumps and Tanks Well Forum & Blog' started by azapplewhite, Jun 10, 2008.

  1. azapplewhite

    azapplewhite New Member

    Joined:
    Jun 10, 2008
    OK, I'm a newbie but I promise I did try to answer this question by reading the pevious threads related to chatter first!

    I just replaced my old pressure pump with a Grundfos 1/2 HP JPS-2A jet pump. This unit comes with SQUARE-D pressure switch attached to the housing, pre-set at 30/50 psi.

    My installation is pretty simple, I'm using the pump as a pressure pump connected to a 119 gallon Flexcon pressure tank which is pre-charged to 28 psi. The pump is gravity fed by a 5,000 gallon cistern so it doesn't have to "suck" any water. All inlet and outlet plumbing is 1" and I have located the pressure tank "as close as possible" to the pump. Total run between pump outlet and pressure tank inlet is only about 3 feet with two 90° bends. I have a 1" check valve right at the pump outlet, this worked fine on my prior installation BUT the pressure switch was located "down stream" of the check valve.

    Once the pressure gets up to about 40 psi the pressure switch starts to "chatter" cutting the pump on and off. Lots of visible arcing across the contacts so I cut power immediately.

    Since there was water @ 40 psi in the tank I carefully bled all the lines (hot and cold water) and made sure there was no trapped air. Alas, that had NO effect, chatter ocurred again once the pressure built up to ~ 40 psi.

    In reading the other posts, I figure that the problem is:
    a) Pressure switch needs to be moved "down stream" of check valve, as close to the pressure tank as possible.
    b) Check valve needs to be moved to pump INLET.
    c) a + b

    Neither of these fixes will be particularly easy but if I'm going to fix it, I'd like to "do it right" and make it as maintenance free as possible for the future. Any advice and suggestions are greatly appreciated!
     
  2. Gary Slusser

    Gary Slusser That's all folks!

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    Retired
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    IMO, you should remove the check valve. I don't see any reason for it. You may have to restrict the flow a bit from the tank to the pump.
     
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  4. azapplewhite

    azapplewhite New Member

    Joined:
    Jun 10, 2008
    Gary, I have no other check valve between my cistern and the pressure tank. I am not that familiar with jet pumps but I assumed, perhaps incorrectly, without a check valve the pressure tank would just force the water backwards, albeit slowly, through the jet pump once it turned off. Does a jet pump act like a check valve, will water only flow one way through it??
     
  5. valveman

    valveman Moderator Staff Member

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    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    You need a check valve. Either move the pressure switch after the check valve, or put the check valve on the pump's suction line.
     
  6. azapplewhite

    azapplewhite New Member

    Joined:
    Jun 10, 2008
    Epilog: Moving the switch worked.

    I thought I'd take a brief moment to say thanks to valveman. I moved the pressure switch "down stream" of the check valve and that did the trick. No more chatter.

    Thanks, Anthony
     
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