another worcester 350 problem - hot water works fine, but on heating mode pressure rises to indicated 3 bar, and water dribbles from pressure release pipe - if the heating stays on for more than about an hour pressure when switched off slowly drops to about .5 bar and low pressure ligth comes on. any ideas?
Expansion vessel will have lost its charge on the air side. Usually just needs pumping up with a foot pump and should be checked as part of a service if you have a reputable heating engineer most engineers ignore this on a service
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