Honeywell RTH5100B Operating Manual page 9

Select the system setting About your new thermostat
Fan System
Auto Heat
Fan System
Auto
CAUTION: EQUIPMENT DAMAGE HAZARD.
To prevent possible compressor damage, do
not operate cooling system when outdoor
temperature is below 50°F (10°C).
Press the SYSTEM button to select
Heat, Cool or Off.
• Heat: Thermostat controls only
the heating system.
• Cool: Thermostat controls only
the cooling system.
• Auto: Thermostat automatically
Cool
selects heating or cooling
depending on the indoor
temperature.
• Off: Heating and cooling
systems are off.
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RTH5100B
69-2330EFS—01