29
tween 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 power
with 24 VAC. Thus, a maximum of 4 wires between the equip-
ment and thermostat is all that is required to operate the sys-
tem.
A
IRFLOW
C
ONSIDERATIONS
Airflow demands are managed differently in a fully communi-
cating system than they are in a non-communicating wired
system. The system operating mode (as determined by the
thermostat) determines which unit calculates the system air-
flow 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 respon-
sible for determining the demand, it calculates the demand
and transmits the demand along with a fan request to the in-
door 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.
System
System
Operating Mode
Airflow Dem and
Source
Cooling
Air Conditioner
Heating
Furnace
Continuous Fan
Thermostat
Cooling
Heat Pump
Heat Pump Heating
Only
Heat Pump
Auxiliary Heating
Furnace
Continuous Fan
Thermostat
Cooling
Furnace
Heating
Furnace
Continuous Fan
Thermostat
F Non-
Comm 1stg Air
Conditioner
Air Condi
Furnace
Heat Pump +
Furnace
For example, assume the system is an air conditioner matched
with a furnace. With a call for low stage cooling, the air condi-
tioner 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 furnace. Once
received, the furnace will send the low stage cooling airflow
demand to the ECM motor. The ECM motor then delivers the
low stage cooling airflow. See the applicable ComfortNet air
conditioner or heat pump installation manual for the airflow
delivered during cooling or heat pump heating.
8. Select the desired “heating” speed tap by positioning
switches 7 and 8 appropriately. Refer to figure above.
Verify CFM by noting the number displayed on the dual
7-segment LED display.
In general lower heating speeds will: reduce electrical consump-
tion, lower operating sound levels of the blower, and increase
the outlet air temperature delivered to the home. The speeds
available allow the blower performance to be optimized for the
particular homeowner’s needs.
B
LOWER
H
EAT
O
FF
D
ELAY
T
IMINGS
The integrated control module provides a selectable heat off
delay function. The heat off delay period may be set to 90, 120,
150, 180 seconds using the DIP switches or jumper provided
on the control module. The delay is factory shipped at 150
seconds but may be changed to suit the installation require-
ments and/or homeowner preference. Refer to the following fig-
ures for switch positions and corresponding delay times.
1
2
90 seconds
OFF
OFF
120 seconds
ON
OFF
150 seconds *
OFF
ON
180 seconds
ON
ON
Heat OF F Delay
DIP Switch No.
Switch Bank: S1
(*Indic ates factory setting)
Heat Off Delay Dipswitches
C
OMFORT
N
ET
™ S
YSTEM
O
VERVIEW
The ComfortNet system is a system that includes a ComfortNet
compatible furnace and air conditioner or heat pump with a
CTK0* thermostat. A valid ComfortNet system could also be a
compatible furnace, CTK0* thermostat and non-compatible,
single stage air conditioner. Any other system configurations
are considered invalid ComfortNet systems and must be con-
nected as a traditional (or legacy) system (
see Electrical Con-
nections
for wiring connections).
A ComfortNet heating/air conditioning system differs from a non-
communicating/traditional system in the manner in which the
indoor unit, outdoor unit and thermostat interact with one an-
other. In a traditional 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 typically do not return information to the thermostat.
In a ComfortNet system, the indoor unit, outdoor unit, and ther-
mostat comprising a ComfortNet system “communicate” digi-
tally with one another. creating 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 CTK0* 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 be-
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