Troubleshooting - Carrier Infinity 50XT-A Installation Instructions Manual

cylinder in upright position and a commercial metering device in
manifold hose. Charge refrigerant into suction line.

TROUBLESHOOTING

LED DESCRIPTION
LEDs built into Infinity control boards provide installer or service
person information concerning operation and/or fault condition of
the unit controls and ECM motor. This information is also
available at the system UI in text with basic troubleshooting
instructions. Careful use of information displayed will reduce the
need for extensive manual troubleshooting. See section B and
Table 2, as well as the UI instructions, for additional information.
Additional Troubleshooting information can be found in Table 7.
MAJOR COMPONENTS
2- -STAGE HP/AC BOARD
The two- -stage HP/AC control board controls the following
functions:
- - Low- - and high- -stage compressor operation
- - Outdoor fan motor operation
- - Reversing valve operation
- - Defrost operation
- - Low ambient cooling
- - Crankcase heater operation
- - Compressor external protection
- - Pressure switch monitoring
- - Time delay
FAN COIL BOARD
The fan coil board controls the following functions:
- - Indoor fan operation
- - Electric heat (if applicable)
SYSTEMS COMMUNICATION FAILURE
If communication with the Infinity Control is lost with the UI, the
controls will flash the appropriate fault codes. Check the wiring to
the UI, indoor and outdoor units.
MODEL PLUG
The HP/AC control board must have a valid model plug to operate.
If a valid model plug is not detected, it will not operate and the
control will flash the appropriate fault code, shown in Table 2.
PRESSURE SWITCH PROTECTION
The unit is equipped with high- - and low- -pressure switches. If the
control senses the opening of a high or low pressure switch, it will
respond as follows:
1. De- -energize the compressor contactor (HPS1 & LPS) or the
compressor solenoid contactor (HPS2).
2. Keep the outdoor fan operating for 15 minutes.
3. Display the appropriate fault codes.
4. After a 15 minute delay, if there is still a call for cooling and
the LPS or HPS is reset, the compressor contactor is
energized.
5. If LPS or HPS has not closed after a 15 minute delay, the
outdoor fan is turned off. If the open switch closes anytime
after the 15- -minute delay, then resume operation with a call
for cooling.
6. If LPS or HPS trips 3 consecutive cycles, the unit operation
is locked out for 4 hours.
7. In the event of a high- -pressure switch trip or high pressure
lockout, check the refrigerant charge, outdoor fan operation
and outdoor coil for airflow restrictions.
8. In the event of a low- -pressure switch trip or low pressure
lockout, check the refrigerant charge and indoor airflow.
CONTROL FAULT
If the HP/AC control board has failed, the control will flash the
appropriate fault code (See Table 2). The control board should be
replaced.
BROWN OUT PROTECTION
If the line voltage is less than 187v for at least 4 seconds, the
appropriate compressor contactor and fan relay are de- -energized.
Compressor and fan operation are not allowed until voltage is a
minimum of 190v. The control will flash the appropriate fault
code (See Table 2).
230V LINE (POWER DISCONNECT) DETECTION
If there is no 230v at the compressor contactor when the unit is
powered and cooling demand exists, the appropriate error code is
displayed. Verify that the disconnect is closed and 230v wiring is
connected to the unit.
COMPRESSOR VOLTAGE SENSING
The control board input terminals VS and L2 (See Fig. 16) are
used to detect compressor voltage status, and alert the user of
potential problems. The control continuously monitors the high
voltage on the run capacitor of the compressor motor. Voltage
should be present any time the compressor contactor is energized,
and voltage should not be present when the contactor is
de- -energized.
CONTACTOR SHORTED DETECTION
If there is compressor voltage sensed when there is no demand for
compressor operation, the contactor may be stuck closed or there is
a wiring error. The control will flash the appropriate fault code.
COMPRESSOR THERMAL CUTOUT
If the control senses the compressor voltage after start- -up, and is
then absent for 10 consecutive seconds while cooling demand
exists, the thermal protector is open. The control de- -energizes the
compressor contactor for 15 minutes, but continues to operate the
outdoor fan. The control Status LED will flash the appropriate
code shown in Table 2. After 15 minutes, with a call for low or
high stage cooling, the compressor contactor is energized. If the
thermal protector has not re- -set, the outdoor fan is turned off. If
the call for cooling continues, the control will energize the
compressor contactor every 15 minutes. If the thermal protector
closes (at the next 15 minute interval), check the unit will resume
operation.
If the thermal cutout trips for three consecutive cycles, then unit
operation is locked out for 4 hours and the appropriate fault code is
displayed.
NO 230V AT COMPRESSOR
If the compressor voltage is not sensed when the compressor
should be starting, the contactor may be stuck open or there is a
wiring error. The control will flash the appropriate fault code.
Check the contactor and control box wiring.
TROUBLESHOOTING UNIT FOR PROPER SWITCHING
BETWEEN LOW & HIGH STAGES
Check the suction pressures at the service valves. Suction pressure
should be reduced by 3- -10% when switching from low to high
capacity.
NOTE: The liquid pressures are very similar between low and
high stage operation, so liquid pressure should not be used for
troubleshooting.
Compressor current should increase 20- -45% when switching from
low to high stage. The compressor solenoid, when energized in
high stage, should measure 24vac.
25