I've no personnal hands on the Sauni Duval boiler but if you are finding the system pressure reaching 3-4bar and you have not manually topped up or left open or partly open the topup valve then the only way this pressure rise is by virtue of the plate to plate heat exchanger. There is a leak from the cold water domestic feed into the heating circuit at the plate exchanger. Shut off cold water inlet v/v to boiler ensure top-up v/v is closed lower system pressure either by venting a rad or drain v/v on CH cct.Not advisable to use Safety Valve as this could damage seat with deris passing thro. Set pressure to 1 bar, run boiler on CH, pressure should approach 1.6bar roughly let it steady. Open coldwater v/v to boiler and run hot tap if pressure rises then leaking plate exchanger
Guytawe, May 2010
