Carrier 50HCQA Installation Manual download pdf (Page 33)

alert. The possible causes are a welded contactor, frozen

compressor relay on MBB, or adverse conditions.

Alert Codes T064 and T065 – Circuit Saturated Condensing

Temp Thermistor Failure

Alert codes T064 and T065 are for circuits A and B respectively.

These alerts occur when the temperature is outside the range –40_

to 240_F (–40_ to 116_C). 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 T066 and T067 -- Circuit Saturated Suction

Temperature Thermistor Failure

Alert codes T066 and T067 are for circuits A and B respectively.

These alerts occur when the unit’s suction transducers are turned

off internally. Cooling will not operate. This is usually due to a

network force on a non exposed CCN point. Reload factory

defaults or reinstall software on the MBB. Consult the network

manager if alert continues.

Alert Code T073 -- Outdoor Air Temperature Thermistor

Failure

This alert occurs 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 economizer

equipped units, the economizer will not operate to provide cooling.

The economizer will still operate for ventilation. 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 Temperature 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

control type is configured 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 Temperature Thermistor

Failure

This alert occurs 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

thermistor, 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. Economizer differential dry bulb

control will not be allowed during 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. If a humidistat is not installed, then

dehumidification will not be functional. Check sensor and wiring.

This alert clears automatically.

NOTE: An ECB must be installed to use the space relative

humidity sensor.

Alert Codes T092 and T093 – Circuit Suction Pressure

Transducer Failure

Alert codes T092 and T093 are for circuits A and B respectively.

These alerts occur when the board does not properly read the

transducer voltage. 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 and T103 - Compressor Current Sensor

Failure

Alert codes T102 and T103 are for compressors A1 and B1,

respectively. These alerts can only occur if the unit is configured to

have compressor current sensors (ConfigurationCOOL

CIR.ACS.A1 or CS.B1). These are not factory installed so would

have to be installed in the field and configured accordingly. 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, a loose connection, or when configured to have the

sensors when they are not actually installed. If the problem cannot be

resolved and the CS board must be replaced, the CS board can be

disabled while securing a replaced board. A CS board is disabled by

setting the corresponding configuration to DISABLE.

Alert Codes T110 and T111 – Circuit Loss of Charge

Alert codes T110 and T111 are for circuits A and B respectively.

These alerts have “Service Test” text that will be displayed if the

alert occurred during service test. 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 pressure alarms (alerts T133 and T134) handle this

situation when the compressor is operating.

Alert Codes T126 and T127 -- Circuit High Discharge Pressure

Alert codes T126 and T127 are for circuits A and B respectively.

These alerts have “Service Test” text that will be displayed if the

alert occurred during service test. These alerts occur when alerts

T051 and T055 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

outdoor ambient temperature coupled with dirty outdoor coil,

plugged filter drier, or a faulty high--pressure switch. See Alerts

T051 and T055 for diagnostic procedure.

Alert Codes T133 and T134 -- Circuit Low Refrigerant

Pressure

Alert codes T133 and T134 are for circuits A and B respectively.

These alerts have “Service Test” text that will be displayed if the

alert occurred during service test. These alerts occur when the

compressor is operating and the evaporating temperature

(converted from the suction 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 4 minutes), or SST.3 (for 3

minutes when using the economizer and 1.5 minutes when not

using the economizer) for the alert to occur. When the outdoor

temperature is less than 40_F, the above values are reduced 1_Ffor

every 2_F the OAT is below 40_F. An alert will also occur if the

circuit SST value is less than SST.3 –5_F for 20 seconds and the

outdoor temperature is above 40_F. All the above timers will reset

if the suction temperature rises above SST.O for 1 minute. These

alerts cause a strike for the respective circuit. If the OAT is less than

10_F, the circuit will shut down without a strike. 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 automatically. 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 return air, or stuck open economizer

when the ambient temperature is low.

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Carrier 50HCQA Installation Manual Page 33

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