Installation manual

531518-UIM-C-0110

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

(13, 15 and 18 SEER premium heat pumps), which continually commu-

nicate 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 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 19.

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 18: Furnace Control Board – Communications Connections

Diagnostic Light

CFM Light