System Switch; Set Temperature Setpoint; Setting F/C Indication And Heat Cycle Rate; Optional System Checkout - Honeywell T8400B Installation Instructions Manual

SYSTEM Switch

System switch settings control thermostat operation as
follows:
Cool: The thermostat controls the cooling system.
Off: Heating and cooling are off.
Heat: The thermostat controls the heating system.
NOTE: Cool Setting availability is model dependent.
Slide the switch in the bottom right corner of the
thermostat to select the desired system setting.

Set Temperature Setpoint

NOTE: Temperature setpoint range is 40° to 99°F
(5° to 37°C).
The setpoint temperature and the room temperature are
shown separately on the digital display. The
points to Set when the setpoint temperature is dis-
played and to Room when the room temperature is
displayed.
Room
Set
SETPOINT TEMPERATURE
To set setpoint temperature:
1. Select Heat or Cool by sliding the system switch
in the lower right corner of the thermostat to the
desired mode. See Fig. 10.
2. To display the setpoint temperature on the digital
display, press either the
setpoint temperature is displayed for approxi-
mately five seconds as the indicator points to Set
and flashes.
M14680
3. To increase the setpoint temperature, press the
key. Each press changes the setpoint one degree;
press and hold to change the setpoint several
degrees.
M14681
4. To decrease the setpoint temperature, press the
key. Each press changes the setpoint one
degree; press and hold to change the setpoint
several degrees.
M14682
indicator
INDICATOR
ROOM TEMPERATURE
M14679
or key once. The
T8400B,C; T8401C ELECTRONIC THERMOSTATS
° °
Setting F/ C Indication and Heat Cycle Rate
NOTE: To save changes to the °F/°C indication and
the heat cycle rate, all seven steps must be
completed.
To set the °F/°C indication and heat cycle rate:
1. If the temperature is displayed in °F, set the
setpoint temperature to 52°F. If the room tem-
perature is displayed in °C, set the setpoint
temperature to 11°C.

Optional System Checkout

When in steps 2 and 3 only, the
used to turn heat or cool outputs on and off.
Change the system switch setting to test heat
or cool outputs. No action takes place if the
system switch is in the Off position.
Examples: System setting at HEAT: If heat is
on, the
off,
System setting at COOL: If cool is
on,
NOTE: The COOL setting is not available on all
models.
2. Press the keys simultaneously for more than
one second to light all segments on display and to
enter installer setup mode. When the keys are
released, a two-digit software revision code is
displayed.
NOTE: In installer setup mode only, each press
of the
Each press of the
displays 02. When the keys are released,
these two-digit codes are no longer
displayed.
5
M14683
key can be
key turns it off; if heat is
turns it on.
M14684
key turns it off; if cool is off,
turns it on.
M14685
M14686
key momentarily displays 01.
key momentarily
69-1494–1