9
3. Check subcooling and superheat. Systems with TXV
application should have a subcooling of 5 to 7°F and
superheat of 7 to 9 °F.
a.
If subcooling and superheat are low,
adjust
TXV to 7
to 9 ºF superheat, then check subcooling.
NOTE:
To adjust superheat, turn the valve stem clock-
wise to increase and counter clockwise to decrease.
b.
If subcooling is low and superheat is high,
add
charge
to raise subcooling to 5 to 7 °F then check super-
heat.
c.
If subcooling and superheat are high,
adjust
TXV
valve to 7 to 9 ºF superheat, then check subcooling.
d.
If subcooling is high and superheat is low,
adjust
TXV valve to 7 to 9 ºF superheat and
remove
charge
to lower the subcooling to 5 to 7 ºF
NOTE:
Do
NOT
adjust the charge based on suction
pressure unless there is a gross undercharge.
4. Disconnect manifold set, installation is complete.
SUBCOOLING FORMULA = SAT. LIQUID TEMP. - LIQUID
LINE TEMP.
NOTE:
Check the Schrader ports for leaks and tighten valve
cores if necessary. Install caps finger-tight.
H
EAT
P
UMP
- H
EATING
C
YCLE
The proper method of charging a heat pump in the heat mode
is by weight with the additional charge adjustments for line
size, line length, and other system components. For best
results on outdoor units with TXVs, superheat should be 2-5°
at 4-6" from the compressor. Make final charge adjustments
in the cooling cycle.
A
DDITIONAL
N
OTES
1. There are (4) LEDs on the PCB. Refer to the
Troubleshooting chart at the end of this manual for
definitions of the LED status.
2. “TERM” dip switch is used for communications bus
configuration. Leave the settings to the factory default
position.
3. “LEARN” push button is used in communication mode
to support device recognition on start-up. As the
communication system supports automatic identification
of both indoor unit and outdoor unit, this button is not
used for a normal start-up.
4. Press “TEST” push button, during system “Standby”
mode to turn on both the compressor and outdoor fan
for five seconds.
5. Press “RECALL” push button to retrieve the six most
recent faults. 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 LEDs will then display the six most recent
faults beginning with the 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. Consecutively
repeated faults are displayed a maximum of three times.
Refer to the fault code definitions at the end of this manual
for more details.
6. A forced defrost can be initiated by pressing “TEST” and
“RECALL” push buttons simultaneously for more than 1
second with a valid call for heat. The forced defrost can
be terminated by
•
A 10 minute lapse in time,
•
A coil temperature rise above 75°F or
•
By pressing the two buttons again for more than 1
second.
C
OMFORT
N
ET
™ S
YSTEM
O
VERVIEW
The ComfortNet system (or CT system) is a system that in-
cludes a ComfortNet compatible air handler/furnace/modu-
lar blower and air conditioner or heat pump with a CTK0*AA
thermostat. Any other system configurations are considered
invalid ComfortNet systems and must be connected as a tra-
ditional (or legacy) system. The following table compares
the valid CT systems.
CT compatible
Air Handler/Furnace/Modular
Blower
CT compatible
Air Conditioner
Full CT system
benefits & features
CT compatible
Air Handler/Furnace/Modular
Blower
CT compatible
Heat Pump
Full CT system
benefits & features
A ComfortNet heating/air conditioning system differs from a
legacy/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 commands to
the indoor and outdoor units via analog 24 VAC signals. It is
a one-way communication path in that the indoor and out-
door units typically do not return information to the thermo-
stat.
On the other hand, the indoor unit, outdoor unit, and thermo-
stat 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 out-
door units. However, the thermostat may also request and
receive information from both the indoor and outdoor units.
This information may be displayed on the CT 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.