I have a Buderus boiler model G124K/25. It is 15 years old, but we have never had any problems with it. Annual service once per year and everything worked fine, we never thought of replacing it… until last weeks when we observed that the gas has been shutting off while the pump stays on. Temperature drops and the boiler doesn’t try to ignite again, we can achieve it by resetting manually. I have no idea what may be the issue, but maybe someone here can help?
Would you please check the value of the water pressure on the boiler pressure gauge? This value should always be around 1.5 bar. Once it gets closer and closer to 0.5 bar boiler will switch off, but you will still be able to reset it and it will pick up the operation. Once pressure value gets under 0.5 bar your boiler won’t ignite at all or will ignite, but will display number of overheating error messages. Try refilling the system by using the directions from the troubleshooting part of this website