Bosche Greenstar pump on every hour

[Reprnow]

Can't fix issue of my Worcester Bosche combi 25i. Since I moved to my new house back in February, I noticed that the pump kicks in every hour or so and the flow can be heard especially in the heaters upstairs. The flow runs for around 3-5min and then stops, the boiler itself remains silent. I got a technician over and he said that the faulty frost protection must be the issue and recommended to change the printed circuit board (PCB). I have changed the PCB with a new one and the problem still isn't fixed. My boiler is in the kitchen and the temperature is certainly not <15 degrees. I am thinking the sensor itself must be at fault, should that be the next step or am I off track here?

 

[cross thread]

Is the eco button on ? This is a preheate for h/w

 

[Reprnow]

Yes, it is on eco mode. Not sure why the pre heat would go on every hour in any case (?). Also doesn't seem like the boiler turns on, only the pump.