While you wait for answers, we may have found some information which could help you.
Click here for Saunier Duval Hot Water Combi
saunier Duval is over pressurising when the heating is on. ?
Saunier Duval F35E auto-vents down to code 21 in minutes?
Saunier Duval Isofast condens F35E....nothing working?
'f19' error report - Saunier Duval 'Thermoclassic' boiler?
How to repair F4 code?
Saunier D’uval therma classuc?