Make sure you have turned the radiators on at both of the valves...increase the pressure to 1 bar, then open the rad. bleed valves to allow them to fill. The pressure will drop as the rads. fill, so close the bleed valves, refill the boiler and continue until all of the air is expelled. Then check the boiler pressure again once done. The pressure release valve (PRV) is simply doing its job - it lets excess water escape, preventing disaster.
John, April 2008