Eliwell AL1

What does Eliwell AL1 mean?

AL1 is the low temperature alarm for probe 1 (Pb1) on Eliwell RTX-600 series controllers. It activates when the Pb1-measured temperature falls below the configured minimum alarm threshold. The alarm is recorded in the ALr alarm folder and has no effect on refrigeration regulation — the controller continues to operate normally.

Symptoms

• Display alternates between 'AL1' and the current Pb1 temperature reading.
• Alarm is logged in the ALr alarm folder.
• Alarm relay activates if configured.
• Buzzer sounds if fitted and enabled.
• Normal refrigeration regulation continues without interruption.

Common causes

• Cabinet or measured zone temperature has dropped below the AL1 low-limit threshold.
• Low alarm limit (AH2 or related parameter) set too close to the operating setpoint.
• Refrigeration system is over-cooling due to a stuck-open expansion valve.
• Pb1 probe is positioned in a cold spot close to the evaporator, reading abnormally low.
• Unusual operating conditions such as very low ambient temperatures.

Diagnostic steps

1. 01

   Read and verify the actual Pb1 temperature

   Navigate to the live data display and compare the Pb1 value with an independent thermometer placed in the same zone to confirm accuracy.

2. 02

   Review the AL1 low-limit alarm parameter

   Enter the programming menu and confirm the AL1 threshold is set appropriately for the application. Adjust if it is set too close to the operating setpoint.

3. 03

   Check Pb1 probe placement

   Verify the probe is positioned in the correct air return location and is not influenced by cold spots near the evaporator coil.

4. 04

   Inspect the refrigeration system for over-cooling

   Check compressor run time and expansion valve operation. A continuously running compressor or wide-open valve may indicate a refrigerant or control issue causing excess cooling.

5. 05

   Acknowledge the alarm

   Press any button to silence the buzzer and clear the alarm LED indicator once the root cause is addressed.

When to call a professional

If temperatures are genuinely below the safe storage limit and adjusting alarm parameters or probe placement does not resolve the cause, a certified refrigeration technician should inspect the expansion valve, refrigerant charge, and controller thermostat parameters to identify the source of excess cooling.