ferroli domina 80E boiler shutting down?

We have an intermittent problem with our ferroli shutting down - no pattern, pleases itself,can behave itself for days then 2/3 times daily. Mainly occurs during switch from domestic back to c/h, but also happens when c/h tries to fire up from standby, at times you can hear a clicking noise. Our gas guy has changed sensors and has suggested a new mother board >> expensive!!! NB, we also have problems with water pressure as noted in other forum issues

John
February 2009