22nd February 2013, 10:42 AM
Viessmann Vitodens 100W - WB1B, F2 temperature limiter fault
Over the last couple of months the boiler has stopped 3 or 4 times with an F2 error code.
Usually it is first thing in the morning, or in the really cold spell, when the frost stat kicked in during the early hours. I have begun to recognise the symptoms as radiators cold, but pump running continuously, and pipes into the pump also cold.
According to the service booklet, F2 is a "temperature limiter" error, and the things to check are:
•system level full
•circulation pump working
•temperature limiter and wiring.
I have checked the system level, and I know the pump is running, but the pump is very likely the original pump and getting on for 30 years old. It's a Grundfos something, but I am wondering about its efficiency, since the furthest radiator does take a while to get hot.
On reset, the boiler display changes from "F2" flashing, to "141", followed by "115degC", then normal operation resumes.
I'd be grateful for any ideas.
13th March 2013, 10:29 PM
sounds like a circulation problem possible pump/air lock or could be a flow switch/sensor my first thought would be air lock presuming the pump is running.