Installation Manual

8
ADDITIONAL NOTES:
1. There are (3) 7-segment LED displays on the PCB. See the
Troubleshooting Tables at the end of this manual for
definitions of the LED status.
2. When system is at Standby mode, press “TEST” push button
to turn on both compressor and outdoor fan for five (5)
seconds.
3. Press “RECALL” push-button to retrieve the six most recent
faults. The control must be in Standby Mode (no
thermostat inputs) to use the feature. Depress the push-
button for approximately two seconds and less than five
seconds. The (3) 7-segment LED displays will then display
the six most recent faults beginning with the most recent
fault and decrementing to the least recent fault. The faults
may be cleared by depressing the button for greater than
five seconds. Consecutively repeated faults are displayed
a maximum of three times. Refer to the fault code
definitions at the end of this manual for more details.
4. “TERM” dipswitch is used for communications bus
configuration. Leave the settings to the factory default
position.
5. “LEARN” push button is used to reset the communications
between the equipment. Used only for troubleshooting
purposes.
C OMFORT N ET ™ S YSTEM
OVERVIEW
The ComfortNet system (or CT system) is a system that includes a
ComfortNet compatible air handler/furnace/modular blower and
air conditioner or heat pump with a CTK0* thermostat. Any other
system configurations are considered invalid ComfortNet systems
and must be connected as a tradition (or legacy) system. The
table below compares the valid CT systems.
CT compatible
Air Handler/Furnace/Modular
Blower
CT compatible
Air Conditioner
Full CT system
benefits & features
CT compatible
Air Handler/Furnace/Modular
Blower
CT compatible
Heat Pump
Full CT system
benefits & features
A ComfortNet heating/air conditioning system differs from a
legacy/traditional system in the manner in which the indoor unit,
outdoor unit and thermostat interact with one another. In a tra-
ditional system, the thermostat sends commands to the indoor
and outdoor units via analog 24 VAC signals. It is a one-way
communication path in that the indoor and outdoor units typi-
cally do not return information to the thermostat.
On the other hand, the indoor unit, outdoor unit, and thermostat
comprising a ComfortNet system “communicate” digitally with
one another. It is now a two-way communications path. The
thermostat still sends commands to the indoor and outdoor units.
However, the thermostat may also request and receive informa-
tion from both the indoor and outdoor units. This information
may be displayed on the CT thermostat. The indoor and outdoor
units also interact with one another. The outdoor unit may send
commands to or request information from the indoor unit. This
two-way digital communications between the thermostat and
subsystems (indoor/outdoor unit) and between subsystems is
the key to unlocking the benefits and features of the ComfortNet
system.
Two-way digital communications is accomplished using only two
wires. The thermostat and subsystem controls are powered with
24 VAC Thus, a maximum of 4 wires between the equipment
and thermostat is all that is required to operate the system.
AIRFLOW CONSIDERATIONS
Airflow demands are managed differently in a fully communicat-
ing system than they are in a legacy wired system. The system
operating mode (as determined by the thermostat) determines
which unit calculates the system airflow demand. If the indoor
unit is responsible for determining the airflow demand, it calcu-
lates the demand and sends it to the ECM motor. If the outdoor
unit or thermostat is responsible for determining the demand, it
calculates the demand and transmits the demand along with a
fan request to the indoor unit. The indoor unit then sends the
demand to the ECM motor. The following table lists the various
ComfortNet™ systems, the operating mode, and airflow demand
source.
System
System
Operating Mode
Airflow Demand
Source
Cooling Air Conditioner
Heating Air Handler
Continuous Fan Thermostat
Cooling Air Conditioner
Heating Furnace
Continuous Fan Thermostat
Air Conditioner +
Air Handler
Air Conditioner +
Furnace
For example, assume the system is an air conditioner matched
with an air handler. With a call for low stage cooling, the air
conditioner will calculate the system’s low stage cooling airflow
demand. The air conditioner will then send a fan request along
with the low stage cooling airflow demand to the air handler.
Once received, the air handler will send the low stage cooling
airflow demand to the ECM motor. The ECM motor then delivers
the low stage cooling airflow. The table below lists the nominal
high and low stage airflow for the ComfortNet heat pumps.
High Low
800 600
1200 800
1550 1100
1800 1400
800 600
1250 850
1550 1070
1750 1210
Model
*SXC160241
*SXC160361
*SXC160481
*SXC160601
*SXC180241
*SXC180361
*SXC180481
*SXC180601