DIY Doctor

PRV or Grundfos MQ Pump causing overflow

Postby Blackrock63 » Wed Sep 02, 2020 6:13 pm

I have a Grundfos MQ series domestic pump and it has started cycling on and off. The pressure at the outlet reaches approx 2 bar of pressure and the pump shuts off. The pressure then immediately drops as it overflows out of the Pressure Relief valve. Once the pressure gets to 1.5 bar the pump kicks in and the cycle of off/on starts again and again.

I have today replaced the pressure relief valve and the pump was fine for about an hour and now it has started to go through the same process of dumping water out the pressure relief valve and cycling through the on/off process of getting up to 2 bar and then losing pressure.

Attached is a short video of it happening and a picture of the pump and PRV.

Does anyone have any ideas as to what the issue may be?

Thanks in advance of any help and support you can provide

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Postby stoneyboy » Fri Sep 04, 2020 8:37 pm

Hi blackrock63
Sounds like you pressure relief valve is set lower than the pump output pressure so try adjusting the PRV for a higher pressure.
Regards S
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