69-1494–1
3
T8400B,C; T8401C ELECTRONIC THERMOSTATS
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.
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.
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.
M11023
ALTERNATE
MOUNTING
SCREW HOLE
MOUNTING
SCREW
HOLE
MOUNTING
SCREW HOLE
ALTERNATE MOUNTING
SCREW HOLE
KEEP WIRING IN
SHADED AREA
WIRING ENTRANCE HOLE
W
Y
G
R
C
Fig. 4. Wiring connections.
M11232
FOR WRAPAROUND
STRIP 7/16 IN. (11 MM)
FOR STRAIGHT INSERTION
STRIP 5/16 IN. (8 MM)
TERMINAL SCREW
W
G
Y
R
C
Fig. 5. T8400B heat-only wiring diagram in a single
transformer system with gas heat.
L1
(HOT)
L2
1
1
W
G
R
FAN
RELAY
HEATING
PRIMARY
CONTROL
24V
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
M10973
T8400B
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.
L1
(HOT)
L2
1
1
W
R
HEAT
PRIMARY
CONTROL
24V
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
M10974
T8400B
