ATAG one random call up

[Grahame Tranmer]

Hello I have an ATAG boiler controlled by an ATAG 1 thermostat been good for three years but now randomly called for heating on full temp ,not good with the current price of gas anyone got any ideas what’s causing this ?
Cheers

 

[Scott_D]

Is it coming on when really cold outside where you are?
Might be trying to achieve the next set temp in a reasonable time?