Ako E24

What does Ako E24 mean?

E24 is the second-evaporator equivalent of E14 on AKO advanced cold room controllers. It indicates that a lack of stability has been detected in the second evaporator circuit, preventing SELFDRIVE from completing its self-calibration. The controller has detected excessive oscillations or door-opening events during the calibration window for the second evaporator.

Symptoms

• E24 appears on the display.
• SELFDRIVE calibration for the second evaporator cannot complete.
• Controller operates the second evaporator in standard (non-SELFDRIVE) mode.
• Alarm relay activates.
• The first evaporator may continue operating in SELFDRIVE mode unaffected.

Common causes

• Excessive door openings during the SELFDRIVE calibration window disrupting the thermal measurements (most common).
• Oscillations in low-side pressure (excessive cycling or unstable expansion valve) on the second evaporator circuit.
• Heavy product loading during calibration causing rapid temperature swings.
• Second evaporator circuit refrigerant charge or expansion valve setting causing pressure instability.
• Probe S3 or S2 positioned where air movement causes rapid temperature fluctuations.

Diagnostic steps

1. 01

   Minimize door openings during calibration

   Allow calibration to run during a low-traffic period (e.g., overnight). Avoid opening the cold room door while E24 is being triggered, as door events reset the calibration stability window.

2. 02

   Inspect the second evaporator expansion valve

   Check for hunting on the expansion valve feeding the second evaporator. Suction pressure oscillations prevent the stable thermal measurements SELFDRIVE requires.

3. 03

   Verify probe positions for S2/S3

   Confirm probes for the second evaporator are not positioned in high-airflow zones where rapid temperature fluctuations occur. Reposition if necessary to a stable measurement point on the coil.

4. 04

   Check aspiration and refrigerant distribution

   Inspect the suction line and expansion valve for the second evaporator circuit. Stable suction superheat and pressures are prerequisites for SELFDRIVE calibration success.

5. 05

   Restart calibration after stabilizing the system

   Follow the AKO manual procedure to restart SELFDRIVE calibration for the second evaporator. Monitor that E24 does not recur after the restart.

When to call a professional

Call a licensed refrigeration technician if E24 recurs after addressing door openings and probe placement, as persistent instability in the second evaporator circuit requires refrigerant system diagnostics — measuring suction superheat, expansion valve response, and refrigerant charge balance across the two evaporator circuits.