APPLICATION
The T8400C Thermostat provides single-stage, non-
programmable temperature control for 24 Vac heating-
cooling systems with manual changeover from heat to
cool. Heating cycle rate is selectable at 1, 3, 4, 5, 6, 9, or
12 cph. Cooling cycle rate is fixed at 3 cph. Temperature
indication can be set for
°
F or
°
C.
The T8400C Thermostat is powered through the heating
and/or cooling system controls.
T8400C includes a thermostat, wallplate (for wiring and
mounting thermostat) and Owner’s Guide.
MERCURY NOTICE
If this control is replacing a control that contains
mercury in a sealed tube, do not place your old
control in the trash. Dispose of properly.
Contact your local waste management authority
for instructions regarding recycling and the
proper disposal of an old control.
X-XX UL
INSTALLATION INSTRUCTIONS
®U.S. Registered Trademark
Copyright © 2002 Honeywell • • All Rights Reserved
T8400C
Electronic Thermostat
INSTALLATION
When Installing this Product…
1. Read these instructions carefully. Failure to follow
them could damage the product or cause a hazard-
ous condition.
2. Check the ratings given in the instructions and on
the product to make sure the product is suitable for
your application.
3. Installer must be a trained, experienced service
technician.
4. After installation is complete, check out product
operation as provided in these instructions.
Caution
Equipment Damage Hazard.
Can short equipment circuitry.
Disconnect power supply before installation.
Location
Install the thermostat about 5 ft (1.5m) above the floor in
an area with good air circulation at average temperature.
See Fig. 1. Do not install the thermostat where it can be
affected by:
—
drafts or dead spots behind doors and in corners.
—
hot or cold air from ducts.
—
radiant heat from the sun or appliances.
—
concealed pipes and chimneys.
—
unheated (uncooled) areas such as an outside wall
behind the thermostat.
This thermostat is a precision instrument and was carefully
adjusted at the factory.
Handle it carefully.
69-1493-1