halstead ace he 30 combi boiler?

boiler is working fine hot water and heating but goes over pressure blows off through pressure release valve. reset pressure but builds up again when in heating mode fine when just hot water.
gareth, December 2013


done
boiler loses pressure
frequent top ups
pressure relief valve leaking
check expansion vessel

http://www.youtube.com/watch?v=uPPUPftBI58

Q, December 2013
could be a partially blocked heat exchanger

A1, December 2013
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