Honeywell RTH5100B - Select the fan setting

Operating Manual
69-2330EFS—01 6
About your new thermostat
System
CoolAuto
Fan
System
CoolOn
Fan
M28303
Select the fan setting
Press the FAN button to select Auto
or On.
In “Auto” mode (the most commonly
used setting), the fan runs only
when the heating or cooling system
is on. If set to “On,” the fan runs
continuously.