Our ecoTEC boiler keeps giving an F22 error. We top up the system and then it's Ok for a week or so before it reoccurs. There's no sign of any leaks in the central heating system and all the radiators have been recently bled.
When the boilers not in use the pressure gauge reads about 0.6 and when in use it reads about 1.0
However occasionally we've seen it in the red part of the gauge and my suspicion is that when this happens an over pressure valve releases some of the water in the system and thus over a period of time, eventually the pressure drops too low - hence the F22 error.
The outside part of the over pressure outlet pipe isn't accessible (as this is a flat) to see if it's wet.
Does this sound like a reasonable diagnosis and if so, what's the likely cause ?

David Rose, January 2009

Many thanks. I'll get a chap in to do it for me :)

David Rose, January 2009

likely that the expansion vessel is either flat or damaged. Think it is internal of the boiler on the right and runs the length (normally grey). It has a valve like that on a car or bike tyre and if you press on it air should come out. If water comes out its knackered if nothing comes out it needs repressurising. Obviosuly isolate any electrical supply if you are attempting any repair yourself.

andy, January 2009