BAXI 105E Instant. System pressurising when on DHW only?

DHW or Primary thermistors could be going out of range, gas valve low gas not set correctly, blockage on the DHW heat exchanger, ignore this previous pos on here about leakage from Heaexchanger - Talking out of their A=se. Easiest thing is get british gas outone off repairs from |£99 inc part and labour for that fault

paul - qualified professional
May 2010

This sounds like a classic case of dhw heating exchanger failure. If system pressure is constantly increasing it can only get this excess pressure from the cold water mains supply via the exchanger.As you are also having hot and cold bursts out of your tap this points towards leaking dhw exchanger I would have thought.

Guytawe
May 2010