987158-UIM-B-1013
12
Johnson Controls Unitary Products
SUPPLY VOLTAGE CONNECTIONS
1. Provide a power supply separate from all other circuits. Install over-
current protection and disconnect switch per local/national electrical
codes. The switch should be close to the unit for convenience in ser-
vicing. With the disconnect or fused switch in the OFF position,
check all wiring against the unit wiring label. Refer to the wiring dia-
gram in this instruction.
2. Remove the screws retaining the wiring box cover. Route the power
wiring through the opening in the unit into the junction box with a
conduit connector or other proper connection. In the junction box
there will be 3 wires, a Black Wire, a White Wire. Connect the power
supply as shown on the unit-wiring label on the inside of the blower
compartment door or the wiring schematic in this section. The black
furnace lead must be connected to the L1 (hot) wire from the power
supply. The white furnace screw must be connected to neutral. Con-
nect the power supply ground to the green screw (equipment
ground) An alternate wiring method is to use a field provided 2” (5.1
cm) x 4” (10.2 cm) box and cover on the outside of the furnace.
Route the furnace leads into the box using a protective bushing
where the wires pass through the furnace panel. After making the
wiring connections replace the wiring box cover and screws. Refer to
Figure 17.
3. The furnace's control system requires correct polarity of the power
supply and a proper ground connection. Refer to Figure 17.
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
(13, 15 and 18 SEER premium heat pumps), which continually commu-
nicate with each other via a four-wire connection called the C-B bus.
Commands, operating conditions, and other data are passed continu-
ally between components over the C-B bus. See Figure 19. 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 also be used along with the Communicating Thermo-
stat Control and a non-communicating outdoor air conditioner through
the addition of a communicating Outdoor Aux Control board to the out-
door unit. This system allows full communication between the furnace
and thermostat and limited communication to the outdoor unit. See Fig-
ure 20.
This furnace may also be used along with the Communicating Thermo-
stat Control and a non-communicating outdoor air conditioner or heat
pump using COMM between the furnace and thermostat and conven-
tional 24V wiring to the outdoor unit. This system allows full communi-
cation between the furnace and thermostat but no digital
communication with the outdoor unit.
FIGURE 17:
Electrical Wiring
Electrical Entry
Junction
Box
L1-Hot
Neutral
Connect ground
lead to screw
BLK
WHT
The power connection leads and wiring box may be relocated to the
left side of the furnace. Remove the screws and cut wire tie holding
excess wiring. Reposition on the left side of the furnace and fasten
using holes provided.
FIGURE 18:
Furnace Control Board – Communications Connections
Diagnostic Light
CFM Light
