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T8112 PROGRAMMABLE THERMOSTAT
CAUTION
Disconnect power before wiring to prevent electrical
shock or equipment damage.
Connect the system wires to the thermostat. See Fig. 3.
A letter code is located near each terminal for
identification.
NOTE: Hold the thermostat as shown in Fig. 4 to
minimize the need for wire extenders.
Securely tighten each terminal screw.
Push excess wire back into the hole.
Plug the hole with nonflammable insulation to prevent
drafts from affecting thermostat operation.
Run the required number of wires to the thermostat
location. Refer to Fig. 5 through 8 for typical wiring
diagrams.
In 5-wire installations only, be sure to remove the factory-
installed jumper connecting the terminals R and Rc.
INSERT
STRAIGHT
5/16 in.
UNDER
(8 mm)
SCREW HEAD
STRIP
END OF WIRE
VISIBLE HERE
Fig. 3. Proper wiring technique.
Fig. 4. Holding thermostat while installing.
68-0170
JUMPER (FACTORY-
INSTALLED) REMOVE
IF 5-WIRE SYSTEM
M1712A
M3002A
4
2-WIRE HEAT-ONLY (JUMPER INTACT)
A
C
B
D
HEATING
RELAY OR
VALVE COIL
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
Fig. 5. 2-wire heat-only application (jumper intact).
3-WIRE COOL-ONLY (JUMPER INTACT)
A
C
B
D
COOLING
CONTACTOR
COIL
FAN
RELAY
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
Fig. 6. 3-wire cool-only application (jumper intact).
JUMPER
W
Y
G
Rc
R
L1
(HOT)
1
L2
M1709B
W
Y
G
JUMPER
Rc
R
L1
(HOT)
L2
M848A
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