Honeywell RTH6400 - Manual (Page 9)

RTH6400 Programmable Thermostat
7 69-22ES—0
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 heat-
ing or cooling system is on. If set to “On,”
the fan runs continuously.
M28405
Set Clock/Day/
Schedule
Auto
Fan System
Heat
M28406
Set Clock/Day/
Schedule
On
Fan System
Heat