ariston microgenius combi MFFI25 trips out 3 times a day???

hi all.
as the title says, my ariston microgenius combi trips out 3 times a day.
it is around 5 years old.
it is more apparent with the heating going constantly. i dont know if i can call up any fault codes on this model. it is the upper red light that comes on, not the chimney symbol.
it has had a problem from day one, but the engineer says that he has set it on the upper limit, to maximise hot water, so occasionally, it will trip, due to water temp! it only happened about once a fortnight, so wasnt a big issue. now it it though.
any advice much appreciated.
thank you for looking.
tony