Ako E20 Error Code

What does Ako E20 mean?

E20 is the second-evaporator equivalent of E10 on AKO advanced cold room controllers (AKO-16526 series). It signals a defrost error on the second evaporator — the defrost cycle did not complete correctly or the evaporator did not reach the defrost end temperature within the maximum allowed defrost time. The controller logs this as an Adt (defrost time-out) condition for the second evaporator.

Symptoms

• E20 appears on the display after a second-evaporator defrost cycle.
• Adt indicator may also appear, confirming defrost ended by maximum time rather than by temperature.
• Second evaporator may still have residual ice after defrost completes.
• Alarm relay activates.
• Defrost end temperature (d4) was not reached within the maximum defrost time (d2) on the second evaporator.

Common causes

• Defrost heaters on the second evaporator are faulty or have insufficient output (most common for electric defrost).
• Defrost end-temperature probe (S2 or S3 on the second evaporator) is positioned away from the coil, causing the end temperature to never be detected.
• Second evaporator has accumulated excessive ice that cannot be cleared within the maximum defrost time.
• Maximum defrost time (d2) parameter is too short for the ice load on the second evaporator.
• Defrost end temperature (d4) is set too low relative to actual heater output capability.

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Diagnostic steps

1. Inspect the second evaporator after defrost

   Immediately after an E20 alarm, inspect the second evaporator for residual ice. Ice remaining after defrost confirms insufficient defrost energy or time.

2. Check defrost heater continuity (electric defrost)

   Measure continuity of the defrost heaters on the second evaporator circuit. A failed heater element will prevent the coil from reaching d4 within d2.

3. Verify defrost end-probe position on second evaporator

   Confirm the defrost termination probe is correctly positioned on the second evaporator coil, not in free air. If it reads air temperature, defrost will time out before the coil-mounted temperature reaches d4.

4. Review d2 and d4 parameter settings for the second evaporator

   Check whether d2 (maximum defrost time) provides enough time for the installed heater capacity to clear the ice load. Increase d2 if the heaters are working but need more time.

5. Manually initiate a defrost and observe completion

   Trigger a manual defrost on the second evaporator and observe whether it completes by temperature (d4 reached) or by time-out (E20). Document which probe reaches the set temperature first to guide further diagnosis.

When to call a professional

Call a licensed refrigeration technician to test and replace defrost heater elements on the second evaporator, as this involves working inside the refrigerated cabinet with electrical components at mains voltage. A technician is also required if the second evaporator's refrigerant circuit is producing excessive ice due to overfeeding or a failed expansion valve.