GMVC9 GCVC9 Installation Instructions

41
AIRFLOW CONSIDERATION
System
System
Operating Mode
Airflow Demand
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
Furnace + Non-
Comm 1stg A ir
Conditioner
Air Conditioner +
Furnace
Heat Pump +
Furnace
Airflow demands are managed differently in a fully commu-
nicating 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 determin-
ing 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 table below lists the various
ComfortNet systems, the operating mode, and airflow de-
mand source.
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
applicable ComfortNet air conditioner or heat pump instal-
lation 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 capability.
During continuous fan operation, the thermostat sends a
fan request along with the continuous fan demand to the
furnace. The furnace, in turn, sends the demand to the
ECM motor. The ECM motor delivers the requested continu-
ous fan airflow.
FOSSIL FUEL APPLICATIONS
This furnace can be used in conjunction with a ComfortNet com-
patible heat pump in a fossil fuel application. A fossil fuel appli-
cation refers to a combined gas furnace and heat pump installa-
tion which uses an outdoor temperature sensor to determine the
most cost efficient means of heating (heat pump or gas fur-
nace). The balance point temperature may be adjusted via
the CTK0* thermostat advanced user menus (see CTK0* in-
structions for additional information).
CTK0* WIRING
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.
12RC
12
RC
CTK0*
Thermostat
ComfortNet Compatible Furnace
Integrated Control Module
ComfortNet Compatible AC/HP
Integrated Control Module
12
R
C
System Wiring using Four-Wires
Figure 54
FOUR-WIRE INDOOR AND OUTDOOR WIRING
Typical ComfortNet wiring will consist of four wires between the
indoor unit and outdoor unit and between the indoor unit and
thermostat. The required wires are: (a) data lines, 1 and 2; (b)
thermostat “R” (24 VAC hot) and “C” (24 VAC common).
TWO-WIRE OUTDOOR, FOUR-WIRE INDOOR WIRING
Two wires can be utilized between the indoor and outdoor units.
For this wiring scheme, only the data lines, 1 and 2, are needed
between the indoor and outdoor units. A 40VA, 208/230 VAC to