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4. TXV-based systems should have a Subcooling value
of 6°F +/- 1°F.
5. Add refrigerant to increase Subcooling and remove
refrigerant to decrease Subcooling.
NOTE: Units matched with indoor coils equipped
with a TXV should be charged by Subcooling only.
Superheat can also be utilized to best verify
charge levels with an adjustable TXV and make
adjustments when needed in unique applications
due to refrigerant line length, differences in
height between the indoor and outdoor unit and
refrigerant tubing sizes. These adjustments
should only be performed by qualified service
personnel.
ADVANCE ADJUSTMENT
RECOMMENDATIONS
1. Clamp a pipe clamp thermometer near the suction line
service valve at the outdoor unit.
a. Ensure the thermometer makes adequate contact
for the best possible readings.
b. The temperature read with the thermometer
should be higher than the saturated suction
temperature.
2. The difference between the measured saturated
suction temperature and the suction line temperature
is the Superheat value.
3. TXV-based systems should have a Superheat value of
8°F +/- 1°F.
4. Adjust Superheat by turning the TXV valve stem
clockwise to increase and counterclockwise to
decrease.
a. If Subcooling and Superheat are low, adjust the
TXV to 8°F +/- 1°F, and then check Subcooling.
b. If Subcooling is low and Superheat is high,
addcharge to raise Subcooling to 6°F +/- 1°F then
check Superheat.
c. If Subcooling and Superheat are high, adjust the
TXV valve to 8°F +/- 1°F Superheat, then check
the Subcooling value.
d. If Subcooling is high and Superheat is low, adjust
the TXV valve to 8°F +/- 1°F Superheat and
remove charge to lower the Subcooling to 6°F +/-
1°F.
NOTE: DO NOT adjust the charge based exclusively
on suction pressure unless for general charging
in the case of a gross undercharge.
NOTE: Check the Schrader ports for leaks and
tighten valve cores if necessary. Install caps
finger-tight.
HEAT PUMP - HEATING CYCLE
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. To
achieve maximum performance, adjust the OD TXV to 8°F
+/- 1°F superheat and subcool below 40° F at 4-6" from the
compressor. Make final charge adjustments in the cooling
cycle.
Low Speed Lock-Out: The outdoor system has a low
speed lock-out feature. In communicating mode, below
37°F outdoor ambient, the system locks out low stage and
operates only in high stage to provide maximum heating
capacity.
Additional Notes
1. There are (3) 7-segment LED displays 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 to reset the
communications between the equipment. Used only
for troubleshooting purposes.
4. Press "TEST" push button, during system "Standby"
mode to turn on both the compressor and outdoor fan
for five seconds.
5. The "RECALL" push button is used 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 7-segment
LED displays 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. 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.
COMFORTBRIDGE™ SYSTEM
Overview
The ComfortBridge based two stage heating and air
conditioning system uses an indoor unit and outdoor unit
digitally communicating with one another via a two-way
communications path.
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