While you wait for answers, we may have found some information which could help you.
Click here for Saunier Boiler YearsSaunier duval Thema F23E. Hot water does not stay constant?
saunier duval isomax c/h and hot water working but not hot?
How can I fix my Saunier Duval 8DN 200v water heater?
i have saunier duval thelia 623 which won't fire the heating any ideas?
how can i relight my saunier duval F23e?
saunier duval 620f?