A.O. Smith Innovo 12-160 Installation, Service & Maintenance Manual page 30

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When the temperature is too low, the water heater starts a operating cycle:
1. The controller detects a "heat demand". The icon "Heat demand present" is shown on
the display of the water heater.
2. The fan starts pre-purging.
3. The air proving switch closes when the air pressure differential is sufficient.
4. The hot surface igniter starts pre-ignition.
5. The gas control valve opens and the gas/air mixture is ignited.
6. The water heater heats the water in the tank. The icon "Water heater in operation" is
shown on the display of the water heater.
7. When the water temperature reaches the setpoint, the heat demand ends and the
controller stops the operating cycle.
The icons "Heat demand present" and "Water heater in operation" on the display turn
off.
8. The fan starts post-purging.
The operating cycle starts again when a new heat demand is detected.
Installation, Maintenance and Service part