Carrier 48PG24 - Page 55

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and there is no current, verify CS wiring and replace if
necessary.
4. Return to Normal mode and observe compressor opera-
tion to verify that compressor current sensor is working
and condenser fans are energized after compressor starts.
Alert Codes T051, T052, T055 and T059 (Current Detected
After Turnoff) — Alert codes T051, T052, T055, and T059
are for compressors A1, A2, B1, and C1, respectively. These
alerts occur when the Current Sensor (CS) detects current
when the compressor should be off. When this occurs, the con-
trol turns off all of the compressors. Use the Scrolling Marquee
to reset the alert.
The possible causes are
1. Welded contactor.
2. Frozen compressor relay on MBB.
To check out alerts T051, T052, T055, and T059:
1. Place the unit in Service Test mode. All compressors
should be Off.
2. Verify that there is not 24 v at the contactor coil. If there is
24 v at the contactor, check relay on MBB and wiring.
3. Check for welded contactor.
4. Verify CS wiring.
5. Return to Normal mode and observe compressor opera-
tion to verify that compressor current sensor is working
and condenser fans are energized after compressor starts.
Alert Codes T064, T065 and T080 (Condensing Temp. Fail-
ure) — Alert codes T064, T065, and T080 are for circuits A, B
and C, respectively. These alerts occur when the temperature is
outside the range –40 to 240 F (–40 to 116 C). When this
occurs, the control will use only the outdoor temperature to
control the outdoor fans. If both the SCT and OAT fail, then
circuit shutdown alarm will occur also. The cause of the alert is
usually a faulty thermistor, a shorted or open thermistor caused
by a wiring error, or a loose connection.
Alert Code T073 (Outdoor Air Temp. Failure)
— This alert oc-
curs when the temperature is outside the range –40 to 240 F
(–40 to 116 C). For all units, all ambient temperature lockout
limits for cooling and heating are ignored. For all units, if both
SCT and OAT fail, then circuit shutdown alarm will also occur.
For economizer equipped units, the economizer will not
operate to provide cooling. The economizer will still operate
for ventilation. For units without Humidi-MiZer™ system, the
control will use condenser temperatures for outdoor fan con-
trol. For Humidi-MiZer system equipped units, the Reheat2
mode will operate at fan level 1. For units with CCH crankcase
heat relay control, the crankcase heat relay will be turned on if
any compressor is off. This alert resets automatically. The
cause of the alert is usually a faulty thermistor, a shorted or
open thermistor caused by a wiring error, or a loose connection.
Alert Code T074 (Space Temp. Failure)
— This alert occurs
when the temperature is outside the range –40 to 240 F (–40 to
116 C). This alert will only occur if the unit control type is con-
figured for Space Sensor (versus Thermostat). Cooling and
heating will not operate. For economizer equipped units, the
economizer will still operate for ventilation. This alert resets
automatically. The cause of the alert is usually a faulty
thermistor in the T-55, T-56, or T-58 device, a shorted or open
thermistor caused by a wiring error, or a loose connection.
Alert Code T075 (Supply Air Temp. Failure)
— This alert oc-
curs when the temperature is outside the range –40 to 240 F
(–40 to 116 C). Economizer cooling and adaptive compressor
staging cannot occur while this alarm is active. This alert resets
automatically. The cause of the alert is usually a faulty ther-
mistor, a shorted or open thermistor caused by a wiring error, or
a loose connection.
Alert Code T076 (Return Air Thermistor Failure)
— This
alert occurs when the temperature is outside the range –40 to
240 F (–40 to 116 C). This alert will only occur if the unit is
configured for a return air sensor. There is no control action as
a result of this alert. This alert resets automatically. The cause
of the alert is usually a faulty thermistor, a shorted or open
thermistor caused by a wiring error, or a loose connection.
Alert Code T077 (Space Relative Humidity Sensor Failure)
— This alert occurs when the input is less than 3.5 mA and the
sensor is configured as installed. Check sensor and wiring. This
alert clears automatically.
Alert Code T080 (Condensing Temp. Failure)
— See Alert
T064.
Alert Codes T092, T093, T101 (Suction Pressure Transducer
Failure) — Alert codes T092, T093, and T101 are for circuits
A, B and C, respectively. These alerts occur when the pressure
is outside the range 0.5 to 134.5 psig. A circuit cannot run
when this alert is active. Use the Scrolling Marquee to reset the
alarm. The cause of the alert is usually a faulty transducer,
faulty 5-v power supply, or a loose connection.
Alert Codes T102, T103, and T104 (Current Sensor Failure)
— Alert codes T102, T103, and T104 are for compressors A1
and A2, B1, and C1, respectively. These alerts occur when the
output of the current sensor (CS) is a constant high value.
These alerts reset automatically. The cause of the alert is a
wiring error or a loose connection. If the problem cannot be
resolved and the CS board must be replaced, the CS board can
be temporarily disabled while securing a replaced board. A CS
board is disabled by setting the corresponding configuration to
DISABLE (Configuration
→ COOL → CIR.A → CS.A1, CS.B1
or CS.C1).
Alert Codes T110, T111, T140 (Loss of Charge)
— Alert
codes T110, T111, and T140 are for circuits A, B and C, re-
spectively. These alerts occur when the compressor is OFF and
the suction pressure is less than 5 psig and OAT is greater than
–5 F for 1 continuous minute. Use the Scrolling Marquee to
reset the alert. The cause of the alert is usually low refrigerant
pressure or a faulty suction pressure. These alerts only occur
when the compressor is OFF because the low refrigerant pres-
sure alarms (alerts T133, T134 and T141) handle this situation
when the compressor is operating.
Alert Codes T126, T127, T142 (High Refrigerant Pressure)
—
Alert codes T126, T127, and T142 are for circuits A, B, and C,
respectively. These alerts occur when alerts T051, T055, or
T059 are active while the appropriate condensing temperature
is greater than 150 F. These alerts reset automatically. The
cause of the alert is usually an overcharged system, high out-
door ambient temperature coupled with dirty outdoor coil,
plugged filter drier, or a faulty high-pressure switch. See Alerts
T051, T055 and T059 for diagnostic procedure.
Alert Codes T133, T134, T141 (Low Refrigerant Pressure)
—
Alert codes T133, T134, and T141 are for circuits A, B and C,
respectively. These alerts occur when the compressor is operat-
ing and the evaporating temperature (converted from the suc-
tion pressure) is less than configured low suction control levels,
Configuration
→ COOL → SST → SST.1 (Low Suction —
Level 1) or SST.2 (Low Suction — Level 2) or SST.3 (Low
Suction Level 3). The circuit SST value must be less than
SST.1 for 5 minutes, SST.2 for 3 minutes, or SST.3 for 1.5 min-
utes for the alert to occur. When the outdoor temperature is less
than 40 F, the above values are reduced by an offset that scales
between 0 and 20 as the outdoor temperature goes from 40 to
0° F. An alert will also occur if the circuit SST value is less than
SST.3 –5 F for 20 seconds. These alerts cause a strike for the
respective circuit. These alerts will activate when the coil
becomes frosted. However, during the 15-minute reset period,
the coils will thaw and strike should clear at restart if there is
nothing else wrong with the circuit. The alert resets automatical-
ly. The cause of the alert is usually low refrigerant charge, dirty
filters, evaporator fan operating backwards, loose or broken
belt, plugged filter drier, faulty transducer, excessively cold