if the pressure is rising and stays inbetween 1 an 2 bar dnt worry this is normal if its rising to 2 and above and only when ch is on chances are your expansion vessel will need recharging with a foot pump dnt worry about pressure though it is safe to use there is a valve in boiler which automatically opens at 3 bar and dumps water outside so chill it wont blow up
x, October 2009