When a hot water outlet is opened, water flows into the inlet of the appliance travelling through a fine mesh water filter.

The water then passes through the volumetric water governor into the bottom chamber of the water section. Water is then released through 2 passages (one determined by setting screw and one via the volume selector), which then passes through the venturi on the outlet of the water valve.

This venturi effect draws the water off the top chamber of the water valve and the pressure of the water in the bottom chamber pushes the diaphragm up and in turn opens the gas valve.

When the water passes out of the water valve, this then flows through to the hydrogenerator, which generates 3VAC to activate the ignition and check the safety devices of the appliance.

The voltage then passes through 2 safety devices, over temperature cut out and a flue safety device. Provided both device are sound, voltage then passes to the ICU (ignition control unit). Simultaneously the ICU starts ignition and sends power to the Pilot Solenoid valve, which in turn opens.

Once a flame is established, the ICU then sends power to the main solenoid which closes, this allows the pilot burner to burn the gas off the top chamber of the gas valve and in turn allows the gas valve to open and the main burner to ignite.

Once the main burner has ignited and rectified, the pilot will eventually extinguish, and the burner is monitored via the flame rod.

At all times while the unit is in operation, the safety devices monitor the appliance and the outlet temperature is displayed on the ICU (internal models only) and if an error occurs, a code is displayed on the ICU