potterton combi 28he

[robert boyd]

potterton combi 28he when calling for hot water a clunking noise can be heard and the digital thermostat rises upto 90+ before cutting out, then when reading drops to about 60+ the boiler fire up again and sends hot water until it reaches 90+ and then the process is repeated,
the heating is unaffected and works fine, anyone know what might be causing this?

 

[AWheating]

hard to say, get a competent person in to diagnose and repair the fault.

welcome to the forum.