A.O. Smith 400A - Manual (Page 22)

4. Changing the Display Units
The display interface to the heater has the option of selecting between degrees and Fahrenheit and degrees Celsius for temperature
displays. This can be found in the "Display Settings" menu. Also in this menu, you may adjust how the backlight operates and the
contrast of the LCD screen.
5. Fault and Warning Conditions
This water heater is equipped with electronic controls that have the ability to monitor almost all aspects of the water heater operation. In
the case that there is an undesirable or unsafe condition that occurs, the water heater controls will detect this condition and determine
the appropriate action. Part of this is displaying the information on the LCD in plain text that accurately describes the condition and
diagnostics information that can be used to correct the issue.
There are two types of conditions that can occur during operation. These are: Warnings and Faults:
• Warnings: This is a non-safety related condition that the control has detected that may cause the water heater to operate in a less
than optimal condition, but does not pose a safety concern.
NOTE: When these conditions occur, continued heating cycles will continue and the heater will attempt to regulate the water in the
tank to the Operating Set Point.
Example of a Warning: