GE GEH Series Service Manual page 45

Dry Tank Test
Upon initial installation, or anytime the power LED is OFF and
power is then disconnected, the water heater will run a dry
tank test before starting the selected heating mode.
The control will run the evaporator fans for 90 seconds and
then start the sealed system. The control will run the sealed
system for 5 minutes and monitor the tank temperature from
the T2 sensor. If the control sees a temperature rise of more
than 1.5 degrees, it assumes the tank is empty, shuts off heat
and displays a warning to fill the tank (a full tank would absorb
the heat and the temperature increase would take longer).
NOTE: If power is lost while the power LED is ON, when
power is restored, the control will resume whatever
heating mode had been operating prior to power loss.
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