ferroli optimax 25c i have no hot water and no ch code f3, now is it, the diverting valve ?how can i check it ,i noticed that it moves up and down some times, when i run the hot water it runs hot for 10 seconds then it goes cold again, then the boiler makes a banging noise. then a (d) comes up on the boiler which is not a code, after that it will reset it self after 5 mins i can run the hot water on test, runs great but no ch this will only allow you to run for 15 min can anyone help paul

paul, March 2009

it could be sludge in system,plate heat exchanger blocked, air seperator dirty it is not that easy to diagnose faults on boilers, but i hope my advise helps if not it is still worth just checking

mr john, April 2009