Carrier 48/50AJ specifications T122 Circuit a High Saturated Suction Temperature

any elements of the control which requires its use including economizer differential enthalpy control.

The RA.RH sensor is located in the return air section near the auxiliary control box. The sensor is a loop powered 4 to 20 mA sensor. This alert resets automatically. The cause of the alert is usually a faulty sensor, a shorted or open sensor caused by a wiring error, or a loose connection. The unit must be con- figured to use the sensor through the Outside Air RH Sensor (Configuration→UNIT→SENS→RRH.S) setting.

T082 (Space Temperature Offset Sensor Failure) — If the unit is configured to use a space temperature sensor and is using a T56 sensor with an offset potentiometer, then the alert will occur if the potentiometer is outside the allowable range. The control will default to the software applicable set point because there is no offset available that may be applied to space temper- ature. The alert will automatically clear. The unit must be con- figured for one of the SPT control options through the Unit Control Type (Configuration→UNIT→C.TYP) configuration.

T090 (Circuit A Discharge Pressure Transducer Failure)

T091 (Circuit B Discharge Pressure Transducer Failure) — Alert codes 090, and 091 are for circuits A and B respectively. These alerts occur when the unit is configured for pressure transducers (Configuration→UNIT→DP.XR) and the pres- sure is outside the range 0.0 to 667.0 psig. A circuit cannot run when this alert is active. Use the scrolling marquee to reset the alert. The cause of the alert is usually a faulty transducer, faulty 5v power supply, or a loose connection. Although the software supports this option, it is not possible at the time of the writing of this specification to order the optional discharge pressure transducers.

T092 (Circuit A Suction Pressure Transducer Failure)

T093 (Circuit B Suction Pressure Transducer Failure) — Alert codes 092, and 093 are for circuits A and B respectively. These alerts occur when the pressure is outside the following ranges:

0.5to 134.5 psig when SP.XR=0, 0.0 to 200.0 psig when SP.XR=1, and 0.0 to 420.0 psig on all 48/50A2,A3,A4,A5 units. A circuit cannot run when this alert is active. Use the scrolling marquee to reset the alert. The cause of the alert is usually a faulty transducer, faulty 5 v power supply, or a loose connection.

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 the compressor is OFF and the suction pressure is less than 5 psig for 48/50AJ,AK,AW,AY units or 18 psig for 48/50A2, A3,A4,A5 units and the OAT is above –5 F for 1 continuous minute. The alert will automatically clear when the suction pressure transducer reading is valid and greater than 15 psig for 48/50AJ,AK,AW,AY units or 54 psig for 48/50A2,A3,A4,A5 units. The cause of the alert is usually low refrigerant pressure or a faulty suction pressure transducer.

P120 (Circuit A Low Saturated Suction Temperature — Compressor A2 Shutdown)

T120 (Circuit A Low Saturated Suction Temperature Alert)

A120 (Circuit A Low Saturated Suction Temperature Alarm)

P121 (Circuit B Low Saturated Suction Temperature — Compressor B2 Shutdown)

T121 (Circuit B Low Saturated Suction Temperature Alert)

A121 (Circuit B Low Saturated Suction Temperature Alarm)

—This alert/alarm is used to keep the evaporator coils from freezing and the saturated suction temperature above the low limit for the compressors.

There will be a start-up delay if the outside-air temperature is too low. When the outdoor ambient is below 60 F, during ini- tial start-up, saturated suction temperature will be ignored for a period of 5 minutes. When Temperatures→REF.T→SSTA or Temperatures→REF.T→SSTB is less than 20 F for 4 minutes, less than 10 F for 2 minutes, less than 0° F for 1 minute or less than –20 F for 20 seconds continuously, the second compressor

of the affected circuit, if it exists, will be shut down with a local alert (P120, P121) and a 10-minute timeguard will be added to the compressor. If saturated suction temperature continues to be less than 20 F for 4 minutes, less than 10 F for 2 minutes, less than 0° F for 1 minute or less than –20 F for 20 seconds continuously then compressor no. 1 will be shut down and then an alert or alarm will be issued.

This failure follows a 3 strike methodology whereby the first two times a circuit goes down entirely, an alert will be gen- erated which keeps the circuit off for 15 minutes before allow- ing the circuit to try again. The third time this happens, an alarm will be generated which will necessitate a manual reset to get the circuit back running. It is important to note that a “strike” is called out only if all compressors in the circuit are off at the time of alert/alarm.

To prevent nuisance alerts, P120 and P121 show up in the alarm history and locally at the display but are not broadcast to the network. To recover from these alerts, a 10-minute holdoff timer must elapse and the saturated suction temperature must rise above 29.32 F. If recovery occurs, staging will be allowed on the circuit again. Again, a “strike” is tied to the circuit going off entirely, not reducing capacity and recovering. Therefore it is possible that multiple P120 or P121 alerts may be stored in alarm history but not broadcast.

If there are 1 or 2 strikes on the circuit and the circuit recov- ers for a period of time, it is possible to clear out the strikes thereby resetting the strike counter automatically. The control must have saturated suction temperature greater than or equal to 34 F for 60 minutes in order to reset the strike counters.

T122 (Circuit A High Saturated Suction Temperature)

T123 (Circuit B High Saturated Suction Temperature) — Alert codes 122 and 123 occur when compressors in a circuit have been running for at least 5 to 30 minutes (Configuration →COOL→H.SST). On 48/50AJ,AK,AW,AY units, this alert code occurs if the circuit saturated suction temperature is great- er than 60 F. On 48/50A2,A3,A4,A5 units, this alert code oc- curs if the circuit saturated suction temperature is greater than 65 F when one compressor is running or 60 F when two com- pressors are running. For all units, the high saturated suction alert is generated and the circuit is shut down. Alert code 122 is for circuit A and 123 for circuit B.

T126 (Circuit A High Head Pressure)

T127 (Circuit B High Head Pressure) — Alert codes 126, and 127 are for circuits A and B respectively. On 48/ 50AJ,AK,AW,AY units, these alerts occur when the appropri- ate saturated condensing temperature is greater 145 F. Prior to the alert, the control will shut down one compressor on a circuit if that circuit's saturated condensing temperature is greater than 140 F. If SCT continues to rise to greater than 145 F, the alert will occur and the circuit's remaining compressor will shut down.

On 48/50A2,A3,A4,A5 units, these alerts occur when the appropriate saturated condensing temperature is greater than 150 F. Prior to the alert, the control will shut down one com- pressor on a circuit if that circuit's saturated condensing tem- perature is greater than 145 F. If SCT continues to rise to great- er than 150 F, the alert will occur and the circuit's remaining compressor will shut down.

The cause of the alarm is usually an overcharged system, high outdoor ambient temperature coupled with dirty outdoor coil, plugged filter drier, or a faulty high-pressure switch.

The alert will clear automatically or when the OAT drops 5° F from the time of the alert.

A140 (Reverse Rotation Detected) — A test is made once, on power up, for suction pressure change on the first activated cir- cuit. The unit control determines failure is as follows:

The suction pressure of both circuits is sampled 5 seconds before the compressor is brought on, right when the

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