Everything works properly when turning on Central Heating and or Hot water when getting in from work. However the main burner extinguishes after approx. 90 minutes of operation. Pilot light is still lit and pump/fan still in operation. Bar Pressure drops from approx.. 1 to 0.4 or there abouts. When switching off Central heating and leaving for approx.. 90 minutes and repressurising system normal operation occurs.

Progmiester, March 2013