boiler is locking out on DHW. Overheating !
Flushed out DHW plate exchanger. Changed both thermistors, C.H overheat stat, dual potentiometer.
Running out of ideas now HELP!!
you would need a gas engineer to check burner pressure on gas valve & adjust if necessary
even though detailed instructions on how to check/adjust minimum & maximum gas burner pressures are listed in boiler manual, you are not qualified to do any gas work