TH8320U AND TH8321U TOUCH SCREEN PROGRAMMABLE THERMOSTATS
7
69-1706
Fig. 16. Typical hookup of multistage heat pump with auxiliary/backup heat (3H/2C heat pump).
Powering the Thermostat
There are two different ways to power the thermostat:
• Batteries (three AAA alkaline).
• 24 Vac Common wire.
Wiring 24 Vac Common
Wire the common side of the transformer to the C screw
of the thermostat wallplate. When installing in a single
transformer system, keep jumper wire between the R
and Rc screws. When installed in a two-transformer
system, use the common from the cooling transformer to
connect to C screw and remove the jumper wire between
the R and Rc screws.
Inserting Batteries (Optional)
If not using a 24 Vac Common to power the thermostat,
install three AAA alkaline batteries (included) in the back
of the thermostat. Make sure the positive and negative
terminals are oriented correctly, as marked on the device.
See Fig.17.
Fig. 17. Installing batteries on thermostat back.
Mounting the Thermostat
1.
Align the terminal screw blocks with the pins on the
back of the thermostat.
2.
Push the thermostat straight onto the wallplate.
See Fig. 18.
R
O/B
Y
G
C
Y2
L
E
AUX
SI
S2
HEAT PUMP
COMPRESSOR 2
COMPRESSOR 1
M19906
CHANGEOVER
VALVE
FAN RELAY
HEAT 2 RELAY
(AUXILIARY HEAT)
R
C
1
1
2
2
3
4
5
6
6
6
3
5
5
OPTIONAL 24 VAC
COMMON CONNECTION
EQUIPMENT
MONITOR
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
FACTORY INSTALLED JUMPER.
OUTDOOR SENSOR REQUIRED IN SYSTEM WITH FOSSIL FUEL BACKUP HEAT THAT IS NOT USING AN EXTERNAL FOSSIL FUEL KIT.
OPTIONAL OUTDOOR OR INDOOR REMOTE SENSOR. AVAILABLE ON SELECT MODELS. WIRES MUST HAVE A CABLE SEPARATE
FROM THE THERMOSTAT CABLE.
MUST CONNECT THE 24 VAC COMMON WHEN USING L. THE TERMINAL IS SHOWN AS EQUIPMENT MONITOR, CAN ALSO BE USED AS
A 24 VAC OUTPUT. SEE "L TERMINAL" SECTION FOR MORE INFORMATION.
"O/B" TERMINAL SET TO CONTROL AS EITHER "O" OR "B" IN THE INSTALLER SETUP.
EMERGENCY
HEAT RELAY
4
OUTDOOR/INDOOR
TEMPERATURE
SENSOR
M19918
BATTERIES (3)
