987158-UIM-B-1013
Johnson Controls Unitary Products
13
CONTROL WIRING USING COMMUNICATING
CONTROLS
Use the wiring diagram below to connect the furnace control, Communi-
cating Control (wall thermostat) and communicating outdoor unit. Be
sure that all of the “A” terminals are connected together, all of the “B”
terminals are connected together, all of the “C” terminals are connected
together and all of the “R” terminals are connected together. See Figure
19. When using a fully communicating system, the large screw termi-
nals (C, G, R, etc.) on the furnace control are not used. The four small
screw terminals in the terminal block on the end of the furnace control
should be used.
When connecting the Communicating Control (wall thermostat) and fur-
nace control to a non-communicating outdoor A/C or heat pump, use
the wiring diagram in Figure 20. The thermostat and furnace will be con-
nected exactly as shown above, but the conventional 24 volt R, C and
Y/Y2 terminals will be used to control the outdoor unit.
CONVENTIONAL LOW VOLTAGE CONTROL WIRING
CONNECTIONS
Install the field-supplied thermostat by following the instructions that
come with the thermostat. With the thermostat set in the OFF position
and the main electrical source disconnected, connect the thermostat
wiring from the wiring connections on the thermostat to the terminal
board on the ignition module, as shown in Figures 21-26, Thermostat
Charts. Electronic thermostats may require the common wire to be con-
nected as shown in Figures 22 - 26. Apply strain relief to thermostat
wires passing through cabinet.
The 24-volt, 40 VA transformer is sized for the furnace components
only, and should not be connected to power auxiliary devices such as
humidifiers, air cleaners, etc. The transformer may provide power for an
air conditioning unit contactor.
AIR CONDITIONER CONNECTIONS
This furnace may be used with single-stage or two-stage air condition-
ing units.
For Single-Stage A/C -
Connect the low voltage wiring as shown in
Figure 21, Thermostat Chart.
For Two-Stage A/C -
Use a two-stage thermostat, connect the low volt-
age wiring as shown in Figure 22, Thermostat Chart.
For Two-Stage A/C using a Single-Stage Thermostat -
connect the
low voltage wiring as shown in Figure 23, Thermostat Chart.
This furnace control board can control a two-stage A/C using only a sin-
gle-stage thermostat. In this case, the furnace control switches between
high cool and low cool based on the calculated cooling load.
FIGURE 19:
Modulating Furnace with Communicating AC or HP
FIGURE 20:
Modulating Furnace with Communicating Thermostat and
non-Communicating AC
A+
R
C
B-
A+
R
C
B-
A+
R
GND
B-
LO
COMP
HI
COMP
O
DHUM
Y1
Y/Y2
W
R
G
C
Touch Screen
Communicating control
Modulating Furnace
Communicating control
Air Conditioner/Heat Pump
Communicating control
A+
R
C
B-
A+
R
B-
LO
COMP
HI
COMP
O
DHUM
Y1
Y/Y2
W
R
G
C
Touch Screen
Communicating control
Modulating Furnace
Communicating control
Non-
Air Conditioner
Communicating
Y
Y2
R
C
C
Set the heat anticipator in the room thermostat to 0.1 amps. Setting it
lower will cause short cycles. Setting it higher will cause the room
temperature to exceed the set points.
Some electronic thermostats do not have adjustable heat anticipa-
tors. They should be set to six cycles per hour. Follow the thermostat
manufacturer's instructions.
