Alarm logic for coolers with installed SCS Controllers

dor / ALr 1*

(* FW version prior to 1574 used fault code 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

 -

The controller has detected either continuous door-open status
exceeding the configured door alarm delay, or an abnormally high
frequency of opening and closing cycles.

1. Check physical door closure: ensure the door is fully closed and unobstructed by internal shelves, product racks or external items.

2. Inspect door alignment and sag: verify that the door hangs square in the frame, seals tightly against the perimeter gasket, and self-closes smoothly. Adjust the hinges or replace worn pivot bushings if door sag is observed.

3. Inspect switch and magnet alignment: check that the door switch and magnetic trigger are securely fastened and aligned within operational tolerance when closed.

4. Test switch operation by connecting to the controller with the AoFrio Field app and verifying that opening and closing the door toggles the digital input state in real time.

5. Replace the switch or wiring harness if the signal is intermittent or non-responsive.

6. Clear the alarm: once the door switch confirms a continuous closed state, the alarm clears automatically.

Read more: 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.  Inspect and clean any dust, lint or debris from the condenser coil fins using a soft brush, vacuum or compressed air.
2. Verify that the condenser fan spins freely, is correctly wired, and runs whenever cooling is called.
3. Ensure the cooler has adequate ventilation clearance from walls and other equipment, and is not positioned near direct sunlight or heat sources.
4. Check that the condenser temperature sensor is securely positioned in its designated mounting clip.
5. Allow the refrigeration system to cool down. The controller automatically resets and resumes compressor operation once the condenser temperature falls below the reset threshold (Cht − htF) for the duration of the reset delay (htr). 

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

ALr 15

(FW 1580 onwards)

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

ALr 21

(FW 1580 onwards)

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 S2 draws too much current. A high current component, such as the compressor, has incorrectly been connected to the S3 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.

ALr 27

(FW 1580 onwards) 

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.

ALr 28

(FW 1580 onwards)

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.

ALr 29

(FW version 1700 onwards)

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.

ALr 30

(FW version 1700 onwards)

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.

ALr 38

(Not available on SCS 800) 

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.

Read more about the Run - Lockout Time alarm

ALr 39

(Not available on SCS 800)

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.

Read more about the Grace Time - Lockout Time alarm

This alarm is normally triggered when the controller power has been shut down manually. This means:

• All outputs connected to the SCS (i.e., compressor, fans, lights) are turned off
• The controller displays OFF and the alarm LED icon on the display
• ALr 48 will appear in the cooler event logs (viewable via AoFrio’s software applications)

To switch power back on, follow the instructions for your controller model. Also see ALr 48 - Manual shutdown (long touch disable).

* For SCS 600 this is available for FW 4028.2 onwards. For SCS 800 this is available for all FW versions. 

When the voltage of a cooler is greater than the maximum run or
start voltage for more than 10 seconds, the SCS controller can
switch off the compressor to protect the asset and trigger an alarm to alert the site manager or staff.

Read how the 'Over voltage' alarm works

When the voltage of a cooler is below the Minimum Start
Compressor Voltage, the SCS controller can switch off the
compressor to protect the asset and trigger an alarm to alert the site manager or staff.

Read how the 'Under voltage' alarm works