Alarm logic for coolers with installed SCS Controllers

dor /

ALr 1* 

The door has been left open. The door may not be closed properly due to sagging and may require adjustment.

1. Close the door to clear this fault. 

For more detail, see:

• Fault logic for cooler doors
• How the 'Door Open' alarm works
• How the 'Excessive Door Open' alarm works

ALr 8

The return air temperature has fallen below the low temperature threshold for longer than the Temperature Out-of-spec Alarm Delay period.

1. Check that the Low Temperature Alarm Input Value is set correctly and is at least 1°C below the Operational Cut-off Temperature Input Value.

ALr 9

The return air temperature has risen above the high temperature threshold.

1. Check that the High Temperature Alarm Input Value is set correctly and is at least 1°C above the Operational Cut-off Temperature Input Value.
2. Check that the Temperature Out-of-spec Alarm Delay is at least 30 minutes longer than the Maximum Defrost Cycle Time.
3. Ensure there are no refrigeration issues.

The temperature of a cooler condenser is higher than the high temperature limit. As a result, the SCS Controller switches off the compressor to protect the asset.

1. Check that nothing is blocking the condenser e.g. boxes
2. Then reset by power cycling. 

If this fault continues to happen, check that the condenser fan is functioning correctly.

For more detail, see how the 'Condenser over temp' alarm works

The condenser has seen multiple overtemperature conditions in a short space of time.

1. Check that nothing is blocking the condenser e.g. boxes
2. Then reset by power cycling. 

If this fault continues to happen, check that the condenser fan is functioning correctly.

For more detail, see how the 'Excessive Condenser Overtemp' alarm works

Either the main temperature sensor probe or the condenser temperature probe (if fitted) has failed. The temperature probe needs replacing. The system will not run while this fault is present. 

1. Replace the temperature probe.

For more detail, see how the 'NTC Failure' alarm works

The compressor has run continuously for the configured time without reaching the setpoint temperature. There are multiple possibilities preventing the system from achieving temperature.

1. There are two actions:

• (For all FW Versions prior to 1574) Write to the “Clear Terminal Alarm” parameter.
• (In all FW versions from 1574 onwards) Reset the system by power cycling off and on.

For more details, see How the 'Terminal Alarm' works

The temperature has dropped below the normal mode setpoint by a specified amount. The product temperature keeps getting colder, even when the compressor is turned off.

1. Check the compressor is correctly wired, and that the “Compressor State” parameter is set correctly.

If this doesn't resolve the issue it may be due to an external secondary compressor relay failure. 

For more details, see how the 'Return Air Under Temperature' Alarm works

The compressor has had repeated over temperature trips equaling the high temperature lockout count, within the specified period (This alarm is disabled by default. Parameter access is available upon request). The condenser sensor keeps seeing a high temperature.

1. Check the condenser is not blocked, and the condenser fan is running.

For more details, see how the 'Max Compressor Starts' alarm works

The loading on S1 draws too much current. A high current component, such as the compressor, has incorrectly been connected to the S1 output.

1. Check the wiring.

The loading on S1 draws too much current. A high current component, such as the compressor, has incorrectly been connected to the S1 output.

1. Check the wiring.

ALr 24

(DUAL firmware only) 

There has been no communication from the HS (High-Side) microcontroller.

1. Contact AoFrio.

ALr 25

(DUAL firmware only)

The HS microcontroller could not be updated after a firmware update using the DUAL code. Statistics cannot be recorded until the HS is updated.

1. Check that the controller has mains power. If so, there is a hardware error, or the HS microcontroller firmware is damaged.
2. Contact AoFrio.

A sensor other than the return-air-sensor has failed. The sensor needs replacing. The system however will continue to run by ignoring this sensor.

1. Replace the sensor.

The NDT defrost has been blocked the maximum number of times. There could be multiple possibilities that are preventing the system to reach its desired temperature. Most likely causes are frozen evaporator coils, low refrigerant charge or slow fan speed.

1. Check the evaporator coils, refrigerant and fan speed.

The compressor has had repeated over pressure trips equaling the Over pressure lockout count within the specified period. (This alarm is disabled by default. Parameter access is available upon request). The compressor is faulty or requires servicing. The condenser coil may be blocked and may require cleaning. 

1 Check the compressor and condenser coil.

The defrost initiation probe has repeatedly triggered defrosts within the min allowable time between defrosts, equaling the Excessive Defrosts Lockout Count. (This alarm is disabled by default. Parameter access is available upon request). The defrost initiation probe is reading a low value within a short time of the compressor turning on.

1. Check that the probe is not touching the evaporator coils, and that the evaporator fan is running.

The controller has not been connected by an application during the Lockout Time. Therefore, the controller has turned off all outputs.

1. Connect to the controller with any SCS application to reset the timer and restart operation.
2. Restart the controller for a "grace" period by entering a PIN code via the keypad.

The controller was not connected by an application during the Run – Lockout Time. Then, the controller was reactivated via a keypad password (additional grace time) but has not been connected by an application during the "grace time – lockout time." Therefore, the controller has turned off all outputs.

1. Connect to the controller with any SCS application to reset the timer and restart operation.