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Pump constantly running and boiler flicking on and turning off

Dear all,

This is my first post on here and any help that I can get would be most appreciated.  I am going to call my plumber on Monday - but would like help understanding something that is happening to my heating system.

We had a powercut today and this made me notice that the boiler was on constantly ( this could have been for a while!)

This led me to notice that our Grundfos UPS3 Pump is constantly on and does not turn off.  We have 3 actuators (UFH, DHW and rads upstairs). We have a secondary return pump on a timer that seems to be working well.  

None of these are on and the actuators seem to be doing their job. 

The boiler is also firing up bit turning off straight after, even when there is no demand.  

All pipes are hot for each of the actuators.  I am by no means a plumber, and would like to understand what is going on here.

Could it be the boiler PCB or the pump? 

Any help ot advice would be greatly appreciated and sorry if I have gone around the houses or misunderstood something.  

I have a trustworthy plumber who I’ll call on Monday, but this one is baffling me somewhat!


  • Jamie Hall
    Jamie Hall Member Posts: 23,286
    Sounds like maybe something in the controls got fried... Is this pump that is always on the one circulating water through the boiler? And the "secondary return pump" is circulating water through the heating zones?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Big Ed_4
    Big Ed_4 Member Posts: 2,785
    edited March 11
    Seems like something is making the call for heat when not needed . Photos posted of the equipment and controls could help .
    I have enough experience to know , that I dont know it all
  • Rma72
    Rma72 Member Posts: 2
    It is all in the airing cupboard.  Would you just like a pictiure of this?