Carrier WeatherExpert 48N2 Controls, Start-Up, Operation, Service, And Troubleshooting page 127

Recovery from this alert is automatic. Reason for error is either a
faulty thermistor in the T55, T56, or T58 device, wiring error, or
damaged input on the MBB control board.
T075 (Return Air Thermistor Failure)
Failure of this thermistor (Temperatures  AIR.T  RAT) will
disable any elements of the control which require its use. Ele-
ments of failure include:
• the calculation of mixed air temperature for SumZ control
• the selection of a mode for VAV units
• economizer differential enthalpy or dry bulb control
• RAT offset control for dehumidification
• return air temperature supply air reset
• fan tracking for building pressure control.
Recovery from this alert is automatic. Reason for error is either
a faulty thermistor, wiring error, or damaged input on the MBB
control board.
T076 (Outside Air Relative Humidity Sensor Fail)
Failure of this sensor (Inputs  REL.H  OA.RH) will disable
any elements of the control which require its use. Elements of
failure include economizer outdoor and differential enthalpy
control. Recovery from this alert shall be automatic. Reason
for error is either a faulty sensor, wiring error, or damaged in-
put on the CEM control board.
T077 (Space Relative Humidity Sensor Failure)
Failure of this sensor (Inputs  REL.H  SP.RH) will disable
any elements of the control which require its use. Elements of
failure include humidification and dehumidification. Recovery
from this alert is automatic. Reason for error is either a faulty
sensor, wiring error, or damaged input on the CEM control
board.
T078 (Return Air Relative Humidity Sensor Fail)
Failure of this sensor (Inputs  REL.H  RA.RH) will disable
any elements of the control which require its use. Elements of
failure include economizer differential enthalpy control, hu-
midification, and dehumidification. Recovery from this alert is
automatic. Reason for error is either a faulty sensor, wiring er-
ror, or damaged input on the CEM control board.
T079 (Mixed Air Relative Humidity Sensor Fail)
Failure of this sensor (Inputs  REL.H  MA.RH) will disable
any elements of the control which require its use. Elements of
failure include humidification and dehumidification prognos-
tics. Recovery from this alert is automatic. Reason for error is
either a faulty sensor, wiring error, or damaged input on the
CEM control board.
T082 (Space Temperature Offset Sensor Failure)
When this failure occurs, there is no offset available that may
be applied to space temperature. Recovery from this alert is au-
tomatic. Reason for error is either a faulty slider potentiometer,
wiring error, or damaged input on the MBB control board.
T090 (Circ A Discharge Press Transducer Failure)
T091 (Circ B Discharge Press Transducer Failure)
The associated circuit becomes disabled whenever this trans-
ducer (Pressures  REF.P  DP.A, DP.B) fails. Recovery from
this alert is automatic. Reason for error is either a faulty sensor,
wiring error, or damaged input on the MBB control board.
T092 (Circ A Suction Press Transducer Failure)
T093 (Circ B Suction Press Transducer Failure)
The associated circuit becomes disabled whenever this trans-
ducer (Pressures  REF.P  SP.A, SP.B) fails. Recovery from
this alert is automatic. Reason for error is either a faulty sensor,
wiring error, or damaged input on the MBB control board.
T094 (Circ A EXV 1 Thermistor Failure)
T095 (Circ A EXV 2 Thermistor Failure)
The associated circuit becomes disabled whenever this therm-
istor (Temperatures  REF.T  ASX1, ASX2) fails. Recovery
from this alert is automatic. Reason for error is either a faulty
sensor, wiring error, or damaged input on one of the EXV con-
trol boards.
T096 (Circ B EXV1 Thermistor Failure)
T097 (Circ B EXV2 Thermistor Failure)
The associated circuit becomes disabled whenever this therm-
istor (Temperatures  REF.T  BSX1, BSX2) fails. Recovery
from this alert is automatic. Reason for error is either a faulty
sensor, wiring error, or damaged input on one of the EXV con-
trol boards.
T098 (Circuit A Liquid Temperature Thermistor Failure)
T099 (Circuit B Liquid Temperature Thermistor Failure)
Failure of this sensor (Temperatures  REF.T  LT.A, LT.B)
will disable any elements of the control which require its use.
Elements of failure include charge determination and prognos-
tics. Recovery from this alert is automatic. Reason for error is
either a faulty sensor, wiring error, or damaged input on one of
the EXV control boards.
T100 (Circ A Liquid Press Transducer Failure)
T101 (Circ B Liquid Press Transducer Failure)
Failure of this sensor (Pressures  REF.P  LP.A, LP.B) will
disable any elements of the control which require its use. Ele-
ments of failure include charge determination and prognostics.
Recovery from this alert is automatic. Reason for error is either
a faulty sensor, wiring error, or damaged input on the SCB con-
trol board.
T110 (Circuit A Loss of Charge)
T111 (Circuit B Loss of Charge)
Alert codes 110 and 111 are for Circuits A and B respectively.
These alerts occur when all the compressors on a circuit are
OFF and the suction pressure is less than 18 psig, if the OAT is
above –5°F for 1 continuous minute. The alert will automati-
cally clear when the suction pressure transducer reading is val-
id and greater than 54 psig. The cause of the alert is usually
low refrigerant pressure or a faulty suction pressure transducer.
T112 (Low Circuit A Charge Detected)
T113 (Low Circuit B Charge Detected)
Alert codes 112 and 113 are for Circuits A and B respectively.
These alerts occur when a charge determination using liquid
sensors test has been run and the charge has been calculated to
be less than Configuration  IAQ  PROG  AC.CL. This re-
sult typically indicates charge should be added to the system.
The alert will automatically clear when the test is re-run and
the charge is calculated to be greater than AC.CL. The cause of
the alert is usually low refrigerant charge.
T114 (High Circuit A Charge Detected)
T115 (High Circuit B Charge Detected)
Alert codes 114 and 115 are for Circuits A and B respectively.
These alerts occur when a charge determination using liquid
sensors test has been run and the charge has been calculated to
be greater than Configuration  IAQ  PROG  AC.CH. This
result typically indicates charge should be removed to the sys-
tem. The alert will automatically clear when the test is re-run
and the charge is calculated to be less than AC.CH. The cause
of the alert is usually high refrigerant charge.
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