Airflow Considerations; Fossil Fuel Applications; Ctk0* Wiring - Goodman CVC9/95 Installation Instructions Manual

In a ComfortNet system, the indoor unit, outdoor unit, and ther-
mostat comprising a ComfortNet system "communicate" digitally
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 ComfortNet 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 sub-
systems (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 equipment and
thermostat is all that is required to operate the system.
A C
IRFLOW 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
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.
System Operating
System
Cooling
Air Conditioner +
Heating
Furnace
Continuous Fan
Cooling
Heat Pump Heating
Heat Pump +
Furnace
Auxiliary Heating
Continuous Fan
Cooling
Furnace + Non-
Comm 1stg Air
Heating
Conditioner
Continuous Fan
Airflow Demand Source
Mode
Air Conditioner
Furnace
Thermostat
Heat Pump
Heat Pump
Only
Furnace
Thermostat
Furnace
Furnace
Thermostat
For example, assume the system is an air conditioner matched
with a furnace. With a call for low stage cooling, the air
conditioner will calculate the system's low stage cooling air-
flow demand. The air conditioner will then send a fan re-
quest 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 appli-
cable ComfortNet air conditioner or heat pump installation
manual for the airflow delivered during cooling or heat pump
heating.
In continuous fan mode, the CTK0* thermostat provides the
airflow demand. The thermostat may be configured for a
low, medium, or high continuous fan speed. The low, me-
dium, and high fan speeds correspond to 25%, 50%, and
75%, respectively, of the furnaces' maximum airflow capabil-
ity. During continuous fan operation, the thermostat sends a
fan request along with the continuous fan demand to the fur-
nace. The furnace, in turn, sends the demand to the ECM
motor. The ECM motor delivers the requested continuous
fan airflow.
F F A
OSSIL UEL PPLICATIONS
This furnace can be used in conjunction with a ComfortNet com-
patible heat pump in a fossil fuel application. A fossil fuel applica-
tion refers to a combined gas furnace and heat pump installation
which uses an outdoor temperature sensor to determine the most
cost efficient means of heating (heat pump or gas furnace). When
used with the CTK0* thermostat, the furnace/heat pump sys-
tem is automatically configured as a fossil fuel system. The
balance point temperature may be adjusted via the CTK0*
thermostat advanced user menus (see CTK0* instructions for
additional information).
CTK0* W
IRING
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
18 AWG 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. One hundred (100) feet is the maximum length of
wire between indoor unit and outdoor unit, or between indoor unit
and thermostat. Wire runs over (100) feet require larger gauge
wire.
F -W I
OUR IRE NDOOR AND
Typical ComfortNet wiring will consist of four wires between the
indoor unit and outdoor unit and between the indoor unit and ther-
mostat. The required wires are: (a) data lines, 1 and 2; (b) ther-
mostat "R" (24 VAC hot) and "C" (24 VAC common).
42
O W
UTDOOR IRING