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Excessive Evaporator Icing

Likely causes

Defrost heater failure or defrost not activating

Check: Measure defrost heater resistance — normal 20~80Ω; open circuit = break; measure heater surface temperature during defrost cycle

What to do: Replace broken heater; replace thermal fuse simultaneously (30% failure rate when heater fails); confirm defrost cycle after replacement

Insufficient defrost cycles — ice accumulation

Check: Check current daily defrost count — showcase recommended 4~6 per day; high ambient humidity requires more; assess adequacy from coil icing condition

What to do: Increase daily defrost to 6 times (when summer humidity is high); immediately manually defrost with high-pressure steam or hot water

Excessive outside air infiltration — high-humidity air accelerates icing

Check: Inspect gasket condition (0.76mm paper test); monitor door open duration — frequent long opening accelerates humid air infiltration

What to do: Replace faulty gasket areas; install automatic door closer; staff training to minimize door open time

Coil temperature not verified after defrost termination

Check: Measure coil temperature immediately after defrost termination — must reach +5~+8°C for complete defrost; below 0°C = incomplete defrost

What to do: Verify heater capacity; readjust defrost termination sensor position; add additional heater if placement is uneven

Field tip

After defrost termination, verify coil reaches +5~+8°C — if below this, icing will recur in the next cycle; heater and termination sensor should always be inspected as a set

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