There Is A Power Outage; You Get A System Error Message - Bryant Non-Programmable thermostat Owner's Manual

What if . . .

There is a power outage

If you lose electricity and have batteries installed, the thermostat will
continue to display the indoor temperature because it has a battery
backup power source. This means that even though your heating and
cooling system doesn't work, you will still be able to monitor your
home's temperature. Your settings will also be saved.

You get a system error message

Here are the possible system error messages and what they mean:
-- The room air sensor reports that the room air temperature is
above 150° or below -50°.
E4 The memory has failed and the thermostat will return to the
default factory settings. Call your heating and cooling dealer.
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