Daikin ComfortNet DX18TC Service Instructions Manual page 31

SERVICING
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 communi-
cating 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.
Cooling
Models
High
*SZC160241 800
*SZC160361 1200
*SZC160481 1550
*SZC160601 1800
*SZC180361 1250
*SZC180481 1750
*SZC180601 1750
Heating
Low High Low
600 800 600
800 1200 800
1100 1550 1100
1210 1800 1210
850 1250 850
1210 1750 1210
1210 1750 1210
CTK0* WIRING
A removable plug connector is provided with the control to
make thermostat wire connections. This plug may be re-
moved, wire connections made to the plug, and replaced. It
is strongly recommended that multiple wires into a single
terminal be twisted together prior to inserting into the plug
connector. Failure to do so may result in intermittent opera-
tion. Typical 18 AWG thermostat wire may be used to wire
the system components. However, communications reliabil-
ity may be improved by using a high quality, shielded,
twisted pair cable for the data transmission lines. In either
case, 100 feet is the maximum length of wire between indoor
unit and outdoor unit, or between indoor unit and thermostat.
1 C CTK0*
Thermostat
2 R
CT™ Compatible
1 2 R C
Modular Blower
Integrated Control Module
CT™ Compatible AC/HP
1 2 R C
Integrated Control Module
T -W O , F
WO IRE UTDOOR OUR
Two wires only may be utilized between the indoor and
outdoor units. For this wiring scheme, only the data line, 1
and 2, are reuired between the indoor and outdoor units. A
40Va, 208/230 VAC to 24 VAC transformer must be installed
int he outdoor unit to provide 24 VAC poiwer to the outdoor
unit's electronic control. The transformer is included with the
CTK)* kit. See instructions for mounting and wiring instruc-
tions. Four wires are required between the indoor unit and
the thermost.
1
1
40VA Transformer (included in
CTK0*** kit)
1
24 VAC
208/230 VAC
System Wiring using Tw-Wires between Furnace and AC/HP
and Four-Wires between Furnace and Thermostat
-W I W
IRE NDOOR IRING
C CTK0*
Thermostat
2 R
CT Compatible
2 R C
Modular Blower
Integrated Control Module
CT Compatible
2 R C
AC/HP Integrated
Control Module
31