T8400C, T8401C AND T8424C,D ELECTRONIC THERMOSTATS
68-0180-3 8

Mounting Thermostat to Wallplate

1. Engage the tabs at the top of the thermostat and wallplate.
2. Swing down the thermostat and press the lower edge of
the thermostat onto the wallplate to latch. See Fig. 10.
Fig. 15. Mounting T8400 or T8401 thermostat to wallplate.
Fig. 16. Mounting T8424 thermostat to wallplate.
SETTINGS AND ADJUSTMENTS

Setting Fan and System Switches

Fan and system settings are controlled manually using the
switches located at the bottom of the thermostat case. See
Fig. 17 or 18.
Fig. 17. T8400 and T8401 temperature
display and system switches.
Fig. 18. T8424 temperature display and system switches.
Fan Switch
Fan switch settings are:
ON: The fan runs continuously. Use for
improved air circulation.
AUTO: Normal setting for most homes. In
cooling, the fan starts and stops with the
cooling equipment. In heating, the fan is
controlled directly by the heating
equipment and may start a few minutes
after the heating equipment turns on (on
M11025B
FAN SYSTEM
Auto On Cool Off Heat
DASHED LINES INDICATE TABS
ON BACK OF THERMOSTAT
FAN SYSTEM
Auto Cool Off Heat
ENGAGE TABS AT TOP
OF THERMOSTAT WITH
SLOTS ON WALLPLATE.
A
BPRESS LOWER EDGE OF
CASE TO LATCH.
Set Room
Set Room
M14677
SYSTEM
Cool Off Heat
Auto On
FAN
DASHED LINES INDICATE TABS
ON BACK OF THERMOSTAT
SYSTEM
Cool Off Heat
Auto On
FAN
ENGAGE TABS AT TOP OF THERMOSTAT
WITH SLOTS ON MOUNTING PLATE.
PRESS LOWER EDGE OF
CASE TO LATCH.

A

B

FAN SYSTEM
Auto On Cool Off Heat
INCREASE
SETTING
DECREASE
SETTING
SYSTEM SWITCH
FAN SWITCH
TEMPERATURE DISPLAY
M11020A
Set Room
SYSTEM
Cool Off Heat
Auto On
FAN
M14678
TEMPERATURE DISPLAY
INCREASE SETTING
DECREASE SETTING
FAN SWITCH
SYSTEM SWITCH