T8400C, T8401C AND T8424C,D ELECTRONIC THERMOSTATS

68-0180-3 6

Fig. 9. T8424 wiring connections.

The T8400C Thermostats steal power through the heating

and cooling system controls and are adaptable to most 4-wire,

18 to 30 Vac heating-cooling systems.

The T8401C and T8424C,D Thermostats are powered directly

from the system transformer and are adaptable to most

5-wire, 18 to 30 Vac heating-cooling systems. Refer to Fig. 10

through 14 for typical wiring hookups.

Fig. 10. T8400C/T8401C heat-cool wiring diagram

in single transformer system with

gas heat/electric cooling.

Fig. 11. T8400C/T8401C heat-cool wiring diagram

in oil heating/electric cooling system. Oil

primary has its own transformer.

Fig. 12. T8424C,D two-stage heat and two-stage cool

system with manual changeover wiring diagram.

TERMINAL
SCREW
M20212
GRCYW1 BO
FOR STRAIGHT
INSERTION STRIP
5/16 IN. (8 MM)
FOR WRAPAROUND
STRIP 7/16 IN. (11 MM)
Y2W2
L1
(HOT)
L2
1
2
1
2
W
Y
G
R
C
COOLING
CONTACTOR
FAN
RELAY
HEATING
PRIMARY
CONTROL
24V
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
IN T8401C INSTALLATIONS, CONNECT C TERMINAL. M11021B
T8400C, T8401C
L1
(HOT)
L1
(HOT)
L2
L2
1
1
2
1
W
Y
G
R
C
2
COOLING
CONTACTOR
FAN
RELAY
OIL PRIMARY
CONTROL
TT
24V
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
IN T8401C INSTALLATIONS, CONNECT C TERMINAL. M11022B
T8400C, T8401C
L1
(HOT)
L2
1
1
W2
Y
G
R
C
1ST STAGE
COOLING
2ND STAGE
COOLING
FAN
RELAY
STAGE-TWO
HEATING
Y2
24V
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED. M20213
T8424
W1 STAGE-ONE
HEATING