Worcester 40CDI - Constant Humming/Running when off

Hi

I have a Worcester 40CDI combination boiler which is working fine when under demand, i.e. hot water when needed and cetral heating when on. However when out of the programmed heating periods the boiler emits a buzzing/humming sound, is lit up and doing something.

If I switch it on and off it goes quiet for a while but then starts humming again. The radiators are not heating up and the economy mode is on so it should not be pre heating hot water (even if it was I would not expect it to be on throughout the night)

I moved into the property in the summer so haven't adjusted anything. Something maybe worth mentioning is that the boiler itself is always "off" and there is a programmable room thermostat that defines the temperatures and periods through the day. The boiler itself is not in its 'timed' mode. Maybe nothing but I thought I should mention it.

Thanks for any advice

One possibility might be that the thermostat is what used to be called a night setback one. They do not turn off but change to a low temperature setting during off periods. Another one might be an inbuilt frost stat if the boiler is in a cold location like the outside wall of a utility room or in a garage.

I did thinkthat but the boiler is in the middle of the house on an internal wall. I think the air temperature is dropping to about 14/15C over night. The thermostat is set to 7C for periods where the heating is not required (during the night and day).

I am wondering if I should set the boiler to 'timed' rather than 'off' and set the thermostat to constantly on. Currently the thermostat is what is turning ithe boiler on and off and maybe that is not properly shutting the boiler off but also does not require heat as the temperature is achieved.

I would certainly try timed first to see what happens.