I have a Ferroli Domina 80E, it is an older combination system. The hot water comes on when the hot tap runs, but switches off and on while running no constant hot water, It works the same way with the central heating and the flame never stay ablaze for longer than one minute at a time.

E. Stanley, November 2008

change the thermistors

p, March 2009

it'll be a primary thermistor problem or possibly auto air vent if its a heat exchanger positioned vent.

iain, November 2008