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Thread: Pump question

  1. #1
    DIY Junior Member mcgyver's Avatar
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    Default Pump question

    3/4hp redjacket shallow jet pump. used strictly for irrigation with no pressure/load produced 8-10 gpm from wellpoint shallow well. No pressure switch on it ie turn it on and motor keeps going. what would happen to the pump if I put it on a zone that only produces 6gpm. i know the pressure will increase but can there be damage to the pump when not able to pump to capacity because of the zone restriction? hope that makes sense..... My pump keeps cutting out after 3-5 minutes( Initially) for 1 minute then on for 1 minute. keeps cycling like this. i think it's a thermal switch that keeps tripping.
    Last edited by mcgyver; 03-28-2008 at 07:35 PM.

  2. #2
    Moderator valveman's Avatar
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    Restricting the pump back to as little as 1 GPM won't hurt a thing. The pressure will be a little higher but, a jet pump should not be able to deliver TOO MUCH pressure, even when restricted to 1 GPM. Restricting the flow will also lower the amp load and should help with not tripping the thermal switch. However, if you have a bad motor or bearing, the overload will still trip and you will have to fix the pump.

  3. #3
    DIY Junior Member mcgyver's Avatar
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    Thanks, thought it was the pump......

  4. #4
    DIY Senior Member Bob1000's Avatar
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    Default Jet Pump

    Quote Originally Posted by valveman View Post
    Restricting the pump back to as little as 1 GPM won't hurt a thing. The pressure will be a little higher but, a jet pump should not be able to deliver TOO MUCH pressure, even when restricted to 1 GPM. Restricting the flow will also lower the amp load and should help with not tripping the thermal switch. However, if you have a bad motor or bearing, the overload will still trip and you will have to fix the pump.
    I thought that the Jet Pump would be able to deliver too much pressure but not too much gpm like the self priming centrifugal pump !!!

    Again I thought that restricting flow would INCREASE amps and that is how some dry running protection systems would work by sensing low amps when there is no water resistance

    Now I am confused
    Last edited by Bob1000; 03-29-2008 at 07:15 AM.

  5. #5
    Moderator valveman's Avatar
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    Jet pumps can deliver more pressure than a self primer but, they usually max out at 58 to 74 PSI. Pumps are "counter intuitive". Amps will decrease when the flow is restricted but, they will not be quite as low as when pumping no water. A Cycle Sensor was designed to be able to set the low amp setting to shut the pump off when the pump is not moving water. However, that is just barely under the amps the pump pulls when it is restricted to 1 GPM. Example; a 1 HP pump pulls 9 amps at full flow. It will only pull 5 amps at 1 GPM but, will still drop to 4 amps when the pump is sucking air.

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