Heating device having the following properties: a heating unit for heating a liquid, a throughflow line, which is connected to the said heating unit, for conducting the heated liquid via a connectable central heating line to at least one connected heat consumer, a return flow line, which is connected to the said heating unit, for returning the cool liquid from the heat consumer out of the said connectable central heating line, a domestic water supply line, a filling line which connects the domestic water supply line to the throughflow line or to the return flow line for the purpose of feeding mains water, a filling valve for controlling the flow of the liquid through the filling line, a pressure sensor, which is attached to the throughflow line or the return flow line, for measuring the pressure of the liquid, and a processor unit, which is connected to the said pressure sensor, for evaluating the measurement data provided by the pressure sensor, wherein the processor unit of the heating device is configured to execute the following steps in an automatic feed mode: - monitoring the measured filling pressure, - opening the said filling valve if it is ascertained that the measured filling pressure falls below a previously defined first threshold value, - closing the filling valve if it is ascertained that the measured filling pressure exceeds a previously defined second threshold value, - closing the filling valve once it has been ascertained that a previously defined first time period has elapsed since the filling valve was opened, characterized in that the processor unit of the heating device is configured such - that it can identify a fault in the pressure sensor; - that it can stop the automatic feed mode if it has been ascertained that there is a fault in the pressure sensor; - that it can start the automatic feed mode if it has been ascertained that the pressure sensor is intact. a heating unit for heating a liquid, a throughflow line, which is connected to the said heating unit, for conducting the heated liquid via a connectable central heating line to at least one connected heat consumer, a return flow line, which is connected to the said heating unit, for returning the cool liquid from the heat consumer out of the said connectable central heating line, a domestic water supply line, a filling line which connects the domestic water supply line to the throughflow line or to the return flow line for the purpose of feeding mains water, a filling valve for controlling the flow of the liquid through the filling line, a pressure sensor, which is attached to the throughflow line or the return flow line, for measuring the pressure of the liquid, and a processor unit, which is connected to the said pressure sensor, for evaluating the measurement data provided by the pressure sensor, wherein the processor unit of the heating device is configured to execute the following steps in an automatic feed mode: - monitoring the measured filling pressure, - opening the said filling valve if it is ascertained that the measured filling pressure falls below a previously defined first threshold value, - closing the filling valve if it is ascertained that the measured filling pressure exceeds a previously defined second threshold value, - closing the filling valve once it has been ascertained that a previously defined first time period has elapsed since the filling valve was opened, characterized in that the processor unit of the heating device is configured such - that it can identify a fault in the pressure sensor; - that it can stop the automatic feed mode if it has been ascertained that there is a fault in the pressure sensor; - that it can start the automatic feed mode if it has been ascertained that the pressure sensor is intact. - monitoring the measured filling pressure, - opening the said filling valve if it is ascertained that the measured filling pressure falls below a previously defined first threshold value, - closing the filling valve if it is ascertained that the measured filling pressure exceeds a previously defined second threshold value, - closing the filling valve once it has been ascertained that a previously defined first time period has elapsed since the filling valve was opened, characterized in that the processor unit of the heating device is configured such - that it can identify a fault in the pressure sensor; - that it can stop the automatic feed mode if it has been ascertained that there is a fault in the pressure sensor; - that it can start the automatic feed mode if it has been ascertained that the pressure sensor is intact.