Boiler keeps coming on for a couple of minutes

My boiler keeps coming on late evening after all the scheduling is finished at 10pm. It firers up for a couple of minutes and then turns off, but still shows 66 degrees on our ideal boiler display not 00 (it says that when turned off) Radiators are not getting warm and water tank isn’t scheduled to come on till the next day, so why is it keep firing up and wasting my gas to do nothing. Any ideas please


  • robgratt
    My boiler, a Worcester Greenstar, had a ‘preheat’ setting that turned the boiler on randomly.
    Yours might do the same. Look in the manual and see if this might be the problem.
  • eezytiger

    Ah, yes. My Vaillant 831 combi has a "comfort" setting for the on demand hot water. It turns the boiler on periodically to keep a small reserve of water warmed up so that taps/shower get hot water a little quicker than without. Once I discovered the function I turned it off and I can't say that anyone has missed it.

    It is enabled on my boiler by setting water temperature to maximum and then back to wherever you want it. To disable the comfort feature you turn water temperature to minimum and then back to where you want it. So potentially easy to set on/off by accident when "messing" with the boiler controls.

  • I found out today by a heating engineer that it’s a motorised switch next to our water cylinder which receives a signal to turn the boiler off, it’s a common problem and just needs to be replaced as it’s sticking.