Danfoss AL

What does Danfoss AL mean?

On the Danfoss AK-RC 204B/205C walk-in controller, AL is the minimum-temperature alarm: the temperature value programmed in parameter A2 has been reached on the control probe. It warns that the room has cooled to the configured low limit, indicating over-cooling or a control fault. The acoustic alarm and alarm relay activate according to the controller's message settings.

Symptoms

• Display shows the AL alarm.
• Control-probe temperature has reached the A2 low limit.
• Acoustic alarm and/or alarm relay activate.
• Product may risk freezing if the low temperature is unintended.

Common causes

• Compressor running continuously due to a stuck contactor or control fault.
• Set point or A2 low-alarm limit configured too high.
• Control probe misplaced or reading lower than the true room temperature.
• Very light load or cold ambient reducing the heat to remove.

Diagnostic steps

1. 01

   Read the alarm

   Confirm AL and compare the control-probe temperature with the A2 limit.

2. 02

   Check set point and limits

   Verify the set point and the A2 low-alarm value are appropriate for the application.

3. 03

   Confirm the compressor stops

   Check that the compressor cycles off at set point; continuous running indicates a stuck relay or control fault.

4. 04

   Verify the probe

   Confirm the control probe is correctly placed so the reading reflects the true room temperature.

When to call a professional

If the compressor will not stop or the room stays too cold after checking settings, a refrigeration technician should diagnose the cause. They can confirm whether a contactor is stuck or a control output has failed. Continuous over-cooling can freeze and damage product in a walk-in, so persistent AL alarms warrant trained inspection of the control and electrical components before losses occur.