19
19.3 Fault Recall
The integrated control module is equipped with a momentary push-button switch that can be used to display the last six
faults on the 7 segment LED display. The control must be in Standby Mode (no thermostat inputs) to use the feature.
Depress the push-button for approximately two seconds and less than five seconds. The LED display will then display the
six most recent faults beginning with the most recent fault and decrementing to the least recent fault. The faults may be
cleared by depressing the button for greater than five seconds.
NOTE:
Consecutively repeated faults are displayed a maximum of three times. Example: A clogged return air filter causes
the air handler’s motor to repeatedly enter a limiting condition. The control will only store this fault the first three
consecutive
times the fault occurs.
20 ComfortNet™ System
20.1 Overview
The ComfortNet system is a system that includes a ComfortNet compatible air handler and air conditioner or heat pump with
a CTK0* thermostat. Any other system configurations are considered invalid ComfortNet systems and must be connected
as a traditional (or non-communicating) system (see the 24 V
OLT
T
HERMOSTAT
W
IRING
- N
ON
-C
OMMUNICATING
T
HERMOSTAT
C
ON
-
NECTIONS
section for details).
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 another. In a traditional system, the thermostat sends com-
mands 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.
On the other hand, the indoor unit, outdoor unit, and thermostat comprising a ComfortNet system “communicate” digitally
with one another. It is now 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 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 pow-
ered with 24 VAC Thus, a maximum of 4 wires between the equipment and thermostat is all that is required to operate the
system.
20.1 Airflow Consideration
Airflow demands are managed differently in a fully communicating 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
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 table below lists the various ComfortNet systems, the
operating mode, and airflow demand source.
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 airflow 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. See the
applicable ComfortNet air conditioner or heat pump installation
manual for the airflow delivered during cooling or heat pump heat-
ing.
In continuous fan mode, the CTK0* thermostat provides the airflow
demand. Depending on which CTK0* thermostat has been installed
three or four continuous fan speeds may be available. If the
thermostat provides three speeds (low, medium, high) they
correspond to 25%, 50% and 75%, respectively, of the air handlers’
System
System
Operating Mode
Airflow Dem and
Source
Cooling
Air Conditioner
Heating
Air Handler
Continuous Fan
Thermostat
Cooling
Heat Pump
Heat Pump Heating
Only
Heat Pump
HP + Electric Heat
Strips
> of Heat Pump or Air
Handler Demand
Electric Heat Strips
Only
Air Handler
Continuous Fan
Thermostat
Air Condi
Air Handler
Heat Pump + Air
Handler
Figure 32
Содержание AVPTC24B14 series
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