Rafal Kaczynski
Dear Simon exceed pressure over than manufacture recommendation mean that there is a fault in your boiler. It could be faulty Vessel ( split diaphragm i n or vessel needs recharging) another fault could be faulty PRV or faulty heat exchanger so I would suggest to get your boiler service and than problem should stop. Exceed pressure could cause a fault to heat exchanger diverter valve or your pipe work so repair could be very expensive. I hope this can help Regards Rafal
