What is the safe temperature range I can set for heating and cooling?
The acceptable temperature range for Heat is 40°F to 90°F (4.5°C to 32°C). For Cool, the acceptable range is 50°F to 99°F (10°C to 37°C). If you attempt to set a temperature outside these ranges, the settings will not change. (Page 18)
From the official Honeywell T6220D Programmable Thermostat manual, page 18
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