Daikin ComfortNet DX7TC Service Instructions Manual page 39

SERVICING
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 information from both the indoor and outdoor units. This
information may be displayed on the CT thermostat. The ndoor
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
communicating 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 calculates 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.
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 air conditioners
and heat pumps.
Models
High
*SZC160241 800
*SZC160361 1200
*SZC160481 1550
*SZC160601 1800
*SZC180361 1250
*SZC180481 1750
*SZC180601 1750
*SZC70241 800
*SZC70361 1200
*SZC70481 1600
*SZC70601 1890
CONTROL WIRING
NOTE: Refer to section Electrical Connections - High Voltage
Connections for 208/230 volt line connections to the air
conditioner or heat pump.
NOTE: A removable plug connector is provided with the
control to make thermostat wire connections. This plug may be
removed, wire connections made to the plug, and replaced. It is
strongly recommended that you do not connect multiple wires
into a single terminal. Wire nuts are recommended to ensure
one wire is used for each terminal. Failure to do so may result in
intermittent operation.
Typical 18 AWG thermostat wire may be used to wire the
system components. 150 feet is the maximum length of wire
recommended between indoor unit and outdoor unit, or
between indoor unit and thermostat.
CTK04 STANDARD WIRING SCHEME:
Two wires may be utilized between the indoor and outdoor
units. For this wiring scheme, only the data lines, 1 and 2,
are required between the indoor and outdoor units. A 40VA,
208/230 VAC to 24 VAC transformer must be installed in the
outdoor unit to provide 24 VAC power to the outdoor unit's
electronic control. The "C" 24V common of the outdoor
transformer should be grounded to the equipment (earth)
ground. The transformer is included with the CTK0* kit. See kit
instructions for mounting and wiring instructions. Four wires are
required between the indoor unit and thermostat.
Cooling Heating
Low High
600 800
800 1200
1100 1550 1100
1210 1800 1210
850 1250
1210 1750 1210
1210 1750 1210
560 800
840 1200
1120 1600 1120
1323 1890 1323
Low
600
800
850
560
840
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