Carrier GEMINI SELECT 38APD025 Operating And Service Manual Download Page 61

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Advanced scroll temperature protection is a form of internal

discharge temperature protection that unloads the scroll com-

pressor when the internal temperature reaches approximately

300 F. At this temperature, an internal bi-metal disk valve

opens and causes the scroll elements to separate, which stops

compression. Suction and discharge pressures balance while

the motor continues to run. The longer the compressor runs un-

loaded, the longer it must cool before the bi-metal disk resets.

See Fig. 66 for approximate reset times.

To manually reset ASTP, the compressor should be stopped

and allowed to cool. If the compressor is not stopped, the motor

will run until the motor protector trips, which occurs up to

90 minutes later. Advanced scroll temperature protection will

reset automatically before the motor protector resets, which

may take up to 2 hours.
Compressor Time Guards — For compressors, the control

will use a Compressor Minimum OFF Time of 2 minutes or a

Compressor Minimum ON Time of 3 minutes.
High Discharge Gas Temperature Protection — Units

equipped with digital compressors have an additional thermis-

tor located on the discharge line, If discharge temperature ex-

ceeds 265 F (129.4 C), the digital compressor will be shut off.

Alarms will also occur if the current sensor board malfunc-

tions or is not properly connected to its assigned digital input. If

the compressor is commanded OFF and the current sensor

reads ON, an alert is generated. This will indicate that a com-

pressor contactor has failed closed. In this case, a special mode,

Compressor Stuck on Control, will be enabled and all other

compressors will be turned off. An alarm will then be enabled

to indicate that service is required. Outdoor fans will continue

to operate. The first outdoor fan stage is turned on immediately.

The other stages of fan will be turned on as required by SCT.

Low Saturated Suction — Several conditions can lead to low

saturated suction alarms. The controls have several override

modes built in which will attempt to keep the unit from

shutting down. Low airflow, low refrigerant charge and

plugged filter driers are the main causes for this condition. To

avoid permanent damage, do NOT repeatedly reset these alert

and/or alarm conditions without identifying and correcting the

cause(s).

Alarms and Alerts —

These are warnings of abnormal

or fault conditions, and may cause either one circuit or the

whole unit to shut down. They are assigned code numbers as

described in Table 26.

Automatic alarms will reset without operator intervention if

the condition corrects itself. The following method must be

used to reset manual alarms (refer to Table 27):

Before resetting any alarm, first determine the cause of the

alarm and correct it. After determining and correcting the cause
of the alarm, enter the Alarm mode indicated by the LED on
the side of the scrolling marquee display. Press

and

until the sub-menu item RCRN “RESET ALL CURRENT

ALARMS” is displayed. Press

. The control will

prompt the user for a password, by displaying PASS and
WORD. Press

to display the default password, 1111.

Press

for each character. If the password has been

changed, use the arrow keys to change each individual charac-
ter. Toggle the display to “YES” and press

. The

alarms will be reset.
DIAGNOSTIC ALERT CODES AND POSSIBLE

CAUSES
T048 (Circuit A Compressor Availability Alert)
T049 (Circuit B Compressor Availability Alert) — Alert

codes 048 and 049 are for circuits A and B respectively. These

alerts occur when two compressors are unavailable to run on a

3 compressor circuit. This alert can only occur on single circuit

unit sizes 040-060 and three compressor circuit unit sizes 70-

100. The control ensures proper oil return by insuring a circuit

does not operate with one compressor for longer than one hour

of cumulative run time.
COMPRESSOR FAILURE ALERTS
T051, T052, T053 (Circuit A Compresser Failures)
T055, T056, T057 (Circuit B Compressor Failures) — Alert

codes 051, 052, 053, 55, 56 and 057 are for compressors A1,

A2, A3, B1, B2, and B3 respectively. These alerts occur when

the current sensor (CS) does not detect compressor current dur-

ing compressor operation. When this occurs, the control turns

off the compressor.

If the current sensor board reads OFF while the compressor

relay has been commanded ON, an alert is generated.
POSSIBLE CAUSES
Compressor Overload — Either the compressor internal over-

load protector is open or the external overload protector (Kri-

wan module) has activated. The external overload protector

modules are mounted in the compressor wiring junction box.

Temperature sensors embedded in the compressor motor wind-

ings are the inputs to the module. The module is powered with