1083294-UIM-C-0615
Johnson Controls Unitary Products
13
CONTROL WIRING
This furnace can be connected to the wall thermostat and outdoor A/C
or heat pump using either conventional low voltage (24 VAC) thermo-
stat wiring OR using four-wire digital communications wiring. To use
conventional low voltage wiring, see the section below entitled “Con-
ventional Low Voltage Control Wiring”. To use four-wire communica-
tions control wiring, see the section below entitled “Control Wiring using
Communicating Controls”.
The Communicating System consists of several intelligent communicat-
ing components including the Communicating Thermostat Control
(touch-screen wall thermostat), modulating variable speed furnace, air
conditioner (15 and 18 SEER premium air conditioners) or heat pump
(15 and 18 SEER premium heat pumps), which continually communi-
cate with each other via a four-wire connection called the A-R-C-B.
Commands, operating conditions, and other data are passed continu-
ally between components over the A-R-C-B. See Figure 18. The result
is a new level of comfort, versatility, and simplicity.
In order to use this furnace in full communications (COMM) mode, it
MUST be installed with the matching touch-screen Communicating
Control (wall thermostat) and an outdoor air conditioner or heat pump
with a fully communicating control.
This furnace may be used with the Communicating Thermostat Control
and a non-communicating outdoor air conditioner by installing the AC
Communicating Control Board Kit to the outdoor unit. This system
allows full communication between the furnace and thermostat and lim-
ited communication to the outdoor unit. See Figure 19.
FIGURE 18:
Furnace Control Board – Communications Connections
CONVENTIONAL
LOW VOLTAGE
TSTAT CONNECTIONS
COMMUNICATING
TSTAT CONNECTIONS
DIAGNOSTIC
LIGHT
LAST
ERROR
BUTTON
CFM
INDICATOR
FLOAT
SWITCH
CONNECTION
TEMP
SENSOR
CONNECTIONS
AUXILIARY
SWITCH
CONNECTIONS
HUMIDISTAT
SELECTION
HI HEAT
DELAY
BLOWER
OFF DELAY
CONTINUOUS
FAN SPEED
HEAT PUMP
SELECTION
AIRFLOW
SELECTION
A+ R C B-
A+ R C B-
A+ R C B-
A+ R C B-
COMMUNICATIONS