F22 is low system pressure, underneath the boiler there are two grey taps, open both (1/4 turn) until the pressure raises into the grey area on the guage then close both.
Ideally, the pressure should be between 1-1.5bar when the system is cold, if you press the - (minus) button below the display, it will show you the pressure in the boiler.
Carefree, December 2010
