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Pressure Switch On MQ-35

  • 09-07-2018 3:54pm
    #1
    itsomana
    Registered Users, Registered Users 2 Posts: 27 ✭


    Hi

    Could someone advise as to what the pressure switch on a Grundfos MQ-35 does?

    Thanks in advance.

    Regards


Comments

  • #2
    K.Flyer
    Registered Users, Registered Users 2 Posts: 8,565 ✭✭✭K.Flyer


    When a tap is open and the pump is running it will push the water at a certain pressure through the system. When the tap closes there is a build up of pressure in the system as the pump keeps running. When a certain built up pressure is achieved the pressure switch stops the pump from running. Conversely, when a tap is opened, the pressure switch quickly detects the drop in pressure and starts the pump again.
    So typically it may start the pump at 2.5 bar and stop the pump at maybe 3.5 - 4 bar.
    What problem are you having.


  • #3
    itsomana
    Registered Users, Registered Users 2 Posts: 27 ✭itsomana


    K.Flyer wrote: »
    When a tap is open and the pump is running it will push the water at a certain pressure through the system. When the tap closes there is a build up of pressure in the system as the pump keeps running. When a certain built up pressure is achieved the pressure switch stops the pump from running. Conversely, when a tap is opened, the pressure switch quickly detects the drop in pressure and starts the pump again.
    So typically it may start the pump at 2.5 bar and stop the pump at maybe 3.5 - 4 bar.
    What problem are you having.



    Today I replaced the flow sensor in my Grundfos MQ 35 as per your clear and concise instructions, thanks by the way.

    When I reassembled the pump, it started to switch off again when the tap was opened but the pump would kick back in again after a few seconds. i opened up the pump again and reseated the floe sensor which has stopped it from cutting out. I am dubious if this is the fix as the pump has worked fine over the weekend on an intermittent basis.

    I had wondered if this issue was being caused by the pressure switch.

    If the pump cuts off again i wil look to replace it as it is 12 years old as the flow sensor, circuit board and capacitor have been replaced in during that time.


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