What temperature ranges are acceptable for heating and cooling?
For heating, the acceptable temperature range is 40°F to 90°F (4.5°C to 32°C). For cooling, the acceptable range is 50°F to 99°F (10°C to 37°C). If your temperature settings don't change, make sure they fall within these acceptable ranges.
From the official Honeywell TH6110D Programmable Digital Thermostat manual, page 18
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