It could be a number of things.
Does the boiler fire up, then stop when the temperature goes too high? Is the fan working? If yes.
1) try it on water only. It is possible that a flow sensor is
not working or 3-way valve stuck in heating mode.
John
January 2010
hmmn same as mine i have no idea what to do!!
olisa
December 2009
Sorry - I can't answer your question, I wish I could - but want to say that my boiler has just thrown up thesame problem!! F.22. I wonder if this is a common problem for a certain batch of boilers? When did you get your boiler installed, please?
Joan
February 2009
F.22 Dry fire protection No water in appliance, pump cable defective, pump
blocked or defective, pump output too low
a
February 2009
I can answer this question...
My Vaillant Turbomax plus boiler is showing a fault code of F.22. ?