1. Pressure gauge on a combi boiler when the central heating is turned off the ideal pressure in the system should be 1 bar
2. When the central heating has been running for a couple of hours it should read between 1 1/2 – 2 bar
Any higher could indicate a problem with the pressure vessel. If the pressure in the system keeps dropping this could indicate a leak or a faulty safety valve, you really should only be repressurising the system 2-4 times a year.