Honeywell T8400B, T8400C, T8401C Installation Instructions Manual
T8400B Thermostat provides single-stage, nonprogrammable temperature control for 24V heat-only
applications. Heating cycle rate is selectable at 1, 3, 4,
5, 6, 9, or 12 cph. Temperature indication can be set for
°F or °C.
The T8400B Thermostat is powered through the heating
system controls.
The T8400C and T8401C Thermostats provide singlestage, non-programmable temperature control for 24V
heating-cooling systems with manual changeover from
heat to cool. Heating cycle rate is selectable at 1, 3, 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/cooling system controls. The T8401C Thermostat is powered directly from the system transformer.
Batteries are not required because setpoints are held
permanently by nonvolatile memory for all models.
All models include a thermostat, wallplate (for wiring
and mounting thermostat) and Owner’s Guide. Two
decorator cover plates (for covering wall marks) are
included for select models.
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.
T8400B,C; T8401C
Electronic Thermostats
INSTALLATION INSTRUCTIONS
INSTALLATION
When Installing this Product…
1. Read these instructions carefully. Failure to follow
them could damage the product or cause a
hazardous 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
Electrical Shock or Equipment Damage
Hazard.
Can shock individuals or 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.
®U.S. Registered Trademark
Copyright © 2002 Honeywell • • All Rights Reserved
69-1494-1
T8400B,C; T8401C ELECTRONIC THERMOSTA TS
NO
NO
Fig. 1. Typical location of thermostat.
Mounting Wallplate and Decorator Cover
Plate (Select Models) to Wall
IMPORTANT
Level only for appearance. The thermostat
functions normally even when not level.
NOTE: All models include a thermostat, wallplate (for
wiring and mounting thermostat) and Owner’s
Guide. Two decorator cover plates (to cover
wall marks) are included for select models.
Mount wallplate and decorator cover plate (select
models) as follows (see Fig. 2):
1. Place the desired decorator cover plate and the
wallplate at the desired location on the wall.
2. Pull the thermostat wire through the entrance hole
on the decorator cover plate, then through the
wallplate entrance hole.
3. Select the two mounting holes that best fit the
application.
4. Fasten the decorator cover plate and the wallplate to
the wall using the anchors and screws provided.
5. After wiring the wallplate, plug the hole to prevent
drafts from affecting the thermostat; see Wiring
section.
YES
5 FEET
[1.5 METERS]
NO
5-3/4 IN. x 5-3/4 IN.
DECORATOR
COVER PLATE
1
1
3-7/8 IN. x 3-7/8 IN. DECORATOR COVER PLATE (SELECT MODELS).
DRILL 3/16 INCH HOLES (IF DRYWALL) OR 7/32 (PLASTER OR WOOD)
2
WHEN USING WALL ANCHORS.
Fig. 2. Mounting decorator cover plate
and wallplate to wall.
M10308
WALL
WALL
ANCHORS (2)
M11041C
2
69-1494–1
2
T8400B,C; T8401C ELECTRONIC THERMOSTA TS
E
KEEP WIRING IN
)
N
L
(
L
L
(
L
4
Wiring
IMPORTANT
Use an 18-gauge maximum wire for wiring the
T8400B,C and T8401C Thermostats.
All wiring must comply with local electrical codes and
ordinances. Disconnect the power supply to prevent
electrical shock or equipment damage.
NOTE: To ensure proper mounting of thermostat,
restrict all wiring to the shaded area on the left
side of the terminals. See Fig. 3.
SHADED AREA
MOUNTING
SCREW HOLE
Fig. 3. Restrict wiring to shaded area.
The shape of the terminals permits insertion of straight
or wraparound wiring connections; either method is
acceptable. See Fig. 4.
ALTERNATE MOUNTING
SCREW HOLE
W
Y
G
R
C
WIRING ENTRANCE HOLE
W
Y
G
R
FOR STRAIGHT INSERTIO
STRIP 5/16 IN. (8 MM)
C
TERMINAL SCREW
Fig. 4. Wiring connections.
MOUNTING
SCREW
HOLE
ALTERNATE
MOUNTING
SCREW HOL
M11023
FOR WRAPAROUND
STRIP 7/16 IN. (11 MM
M11232
The T8400B Thermostat is powered through the heating
system control. The T8400B is adaptable to most 2-wire
and 3-wire 18 to 30 Vac heating systems. Refer to Fig. 5
and 6 for typical wiring hookups.
T8400B
W
R
1
1
HOT)
24V
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
1
OVERLOAD PROTECTION AS REQUIRED.
Fig. 5. T8400B heat-only wiring diagram in a single
transformer system with gas heat.
T8400B
W
G
R
1
1
HOT)
24V
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
1
OVERLOAD PROTECTION AS REQUIRED.
Fig. 6. T8400B heat-only wiring diagram in a single
transformer system with gas heat.
The T8400C Thermostat is powered through the
heating/cooling system controls and is adaptable to
most 4-wire, 18 to 30 Vac heating-cooling systems.
The T8401C Thermostat is powered directly from the
system transformer and is adaptable to most 5-wire, 18
to 30 Vac heating-cooling systems. Refer to Fig. 7 and 8
for typical wiring hookups.
3
HEATING
PRIMARY
CONTROL
HEAT
PRIMARY
CONTROL
69-1494–1
M1097
FAN
RELAY
M10973
Loading...