F1 is 'Ignition Lockout' ie. either no gas or no flame detection
As for the system water pressure, that boiler should not foault on this until the water is outside of 0.5 - 2.7 bar pressure.
Normal system cold pressure should be about 1-1.5 bar, if when hot it exceeds 2.5 there may be also a problem with your expansion vessel.
T
April 2008
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