it's the same as a vokera compact. check the filling loop is closed firstly. if it only happens when heating is on then faulty expansion vessel or bloked expansion pipe (common on this boiler). if constantly over pressurising then main heat exchanger is burst internally (no plate to plate heat ex on this oiler)
Ian, September 2009
Never worked on one of these, Need more info, but if it does it when its in heating mode, likely expansion vessel defect. If it does it while its not running plate to plate heat exchanger is split internally
