Pressure has risen to 3 bar where it sits fairly consistently.

Water is continuously flowing out off overflow pipe on roof.

Any suggestions?

puzzled, October 2009

Common problem with this boiler . Combined heat exchange . They break down and leak. the mains water is leaking across, new heat exchange required

Mick, November 2009

filling loop tap not closed properly?. Does the problem go away if you turn of the DHW inlet tap and depressurise the dhw system by opening a hot water tap (possible leak across the dhw heat exchanger if so). If it only happens when system hot, and pressure drops very low when cold its the expansion vessel.

c, October 2009