On a ideal logic boiler, as far as I know there is only one test point for gas pressure on the incoming isolation valve/integral testpoint. Operating pressure is showing as 18mbar which seems a little low. The manual states that The external gas cock could further reduce the operating pressure when measured at its test point. The pressure drop is relative to the heat input to the boiler (kW) (approx 1.5mbar), I have come across WB boilers where there is a pressure drop between the isolation valve and the gas valve, but cannot see how the boiler could affect the measurement at the isolation valve. Has anyone else got experience of these ideal boilers?