Can you tell me the model of your programmer, if you have a room stat , a hot water cylinder stat and if you have two motorised valves or one ,please. I set the wall controls so that the heating would only come on if it was below 22 degrees (which it hasn't been yet) but noticed that the boiler is constantly making a noise. To get the pump to stop going I have to turn off the boiler at the mains. The boiler I inspected yesterday kept turning on and off like this. The control system generally comprises several components, a programmer, a thermostat, a motorized valve and finally the boiler and pump. The pressure didn’t appear to go down at all before the unit came back on… The system should be checked to determine what is powering the boiler and pump, it could be any of these components. Even when you shut off the heat at the programmable thermostat the boiler keeps running. Problem: The boiler keeps running even though the thermostat is not calling for heat (the receiver in the boiler room lights up when the thermostat is calling for heat). The only thing that will fire the boiler when it is off at the programmer is the frost stat. Boiler is about 5 years old as is the thermostat. It'll run the CH for 5 minutes, then turn off for 5 minutes, repeat. This issue has been going on for sometime but gradually getting worse (pump runs for longer and longer). Turned the heating on today for an hour, worked well, then noticed that well after the hour was up and the programmer switched off, the boiler (Ideal ICOS HE15) was still running, with a call for heat. The CH works fine, but sometimes, when it’s been on, the boiler continues to fire and the pump in the airing cupboard continues to run, after it should have gone off, ie the boiler programmer shows that the CH (and HW) is off, but the boiler and pump keep running. The boiler recently started to fire occasionally when the timer was off and the pump runs even though the timer is off. Vaillant boiler firing up when heating is off I've moved into a new flat that has a vaillant boiler. I replaced the thermostat to no avail. Hi , OK ,helps now have the model of your boiler. The pressure was 27 psi and the water temp was only 100 degrees. The programmer indicates that everything is off but the boiler power light still stays on. I am wondering whether it is the Honeywell aquastat controller.I have model L4080b on the boiler. :help:I have a two zone Smith GB100W gas boiler that still runs after the thermostat has reached the desired temp. Is it normal for a boiler system to run for 3-5 minutes or so and then shut off for a minute or two and start back up again? Even if I turn the thermostat off, the boiler keeps running. Be very careful if your boiler is outside and you are turning it off at the fused spur. 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