There Is A Power Outage; You Get A System Error Message - Carrier Comfort Series 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.

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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