10
A
IRFLOW
C
ONSIDERATION
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 de-
termining the demand, it calculates the demand and trans-
mits the demand along with a fan request to the indoor unit.
The indoor unit then sends the demand to the ECM motor.
The table below lists the various ComfortNet systems, the
operating mode, and airflow demand source.
Sys te m
Sys te m
Ope rating M ode
Airflow De m and
Source
Cooling
Heat Pump
Heat Pump Heating
Only
Heat Pump
HP + Electric Heat
Strips
> of Heat Pump or A ir
Handler Demand
Electric Heat Strips
Only
A ir Handler
Continuous Fan
Thermostat
Cooling
Heat Pump
Heat Pump Heating
Only
Heat Pump
A uxiliary Heating
Furnace
Continuous Fan
Thermostat
Heat Pump + A ir
Handler
Heat Pump +
Furnace
For example, assume the system is a heat pump matched
with an air handler. With a call for low stage cooling, the
heat pump will calculate the system’s low stage cooling air-
flow demand. The heat pump 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 follow-
ing table lists the nominal high and low stage airflow for the
ComfortNet™ heat pumps.
High
Low
High
Low
*SZC160241
800
600
800
600
*SZC160361
1200
800
1200
800
*SZC160481
1550
1100
1550
1100
*SZC160601
1800
1210
1800
1210
*SZC180361
1250
850
1250
850
*SZC180481
1750
1210
1750
1210
*SZC180601
1750
1210
1750
1210
Cooling
He ating
M ode ls
CTK0*AA W
IRING
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 multiple wires into a single
terminal be twisted together prior to inserting into the plug
connector. Failure to do so may result in intermittent
operation.
Typical 18 AWG thermostat wire may be used to wire the
system components. However, communications reliability
may be improved by using a high quality, shielded, twisted
pair cable for the data transmission lines. In either case, 150
feet is the maximum length of wire between indoor unit and
outdoor unit, or between indoor unit and thermostat.
F
OUR
-W
IRE
I
NDOOR
AND
O
UTDOOR
W
IRING
Typical wiring will consist of 4 wires between the indoor unit
and outdoor unit and between the indoor unit and thermo-
stat. The required wires are: (a) data lines, 1 and 2; (b) ther-
mostat “R” (24 VAC hot) and “C” (24 VAC common).
1
2 R C
1
2 R C
CTK0*AA
Thermostat
CT Compatible
Air Handler/Furnace/Modular Blower
Integrated Control Module
CT Compatible AC/HP
Integrated Control Module
1
2 R C
System Wiring Using Four-Wires
T
WO
-W
IRE
O
UTDOOR
, F
OUR
-W
IRE
I
NDOOR
W
IRING
Two wires only 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 out-
door unit to provide 24 VAC power to the outdoor unit’s elec-
tronic control. The transformer is included with the CTK0*AA
kit. See kit instructions for mounting and wiring instructions.
Four wires are required between the indoor unit and thermo-
stat.
NOTE:
Use of the CTK0*AA transformer is recommended if
installing a dual fuel system. Failure to use the transformer in
the outdoor unit could result in over loading of the furnace
transformer.