pressure on boiler keeps going up to over 3bar safety valve not c?

it could be the expansion tank has lost its charge or is faulty.the pressure would increase when the system started to get hot. to test the pressure make sure that the boiler is drained and test with a footpump and pressure guage should read between 0.5-1.0 bar. if the pressure goes up even when the heating is not on i would be looking at firstly the filling loop to make sure it is fully shut off.

pete
May 2009