Central Heating Pump Overrun - Valve Closed

Discussion in 'Electricians' Talk' started by RichardSA, Nov 6, 2018.

  1. RichardSA

    RichardSA New Member

    After the boiler has stopped and the pump is over running the motorised valve is closed and the pump is noisier than normal. Should the valve be closed? I presume the pump is trying to force the hot water into the bypass. The system is S Plan with Potterton Profile 80 boiler, Grundfoss pump, Drayton ZA5 2 way valves and Horstmann H27XL programmer. All three boiler thermostats have been replaced. Thanks.
     
  2. Mike83

    Mike83 Active Member

    What bypass is installed.
    It’s correct for the valves to be closed.
     
  3. RichardSA

    RichardSA New Member

    It is an Invensys automatic bypass valve currently set at 0.4
     
  4. Mike83

    Mike83 Active Member

    Is the system all working ok?
    Is it just noise from the pump?
     
  5. RichardSA

    RichardSA New Member

    Yes. System has had overheating problems and pump running when heating turned off. That's why the boiler thermostats were replaced. Think it's OK now.
     
  6. Mike83

    Mike83 Active Member

    The pump noise could be due to the bypass not passing enough water after the zone valves have closed. This could lead to overheating.

    The overheating issue could be due to incorrectly positioned stats on the boiler or circulation issues.

    Does the pump continue to run once the system is cool?
     
  7. RichardSA

    RichardSA New Member

    No. The pump overrun now seems to be working as it should. I may try turning the bypass pressure down.
     

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