Troubleshooting: Frozen Evaporator Coil in Fruit Ripening Room

1. Common Symptoms

Coil fully frosted / iced over; poor air flow

Uneven room temperature & humidity

Weak cooling effect; ripening speed abnormal

Excessive condensate or blocked drain pan/drain line

2. Root Causes & Solutions

① Low evaporating temperature / Low suction pressure (Main cause)

Reason: Refrigerant charge insufficient; expansion valve fault; system pressure set too low.

Solution:

Check & adjust suction pressure to match ripening room design.

Recharge refrigerant to rated volume.

Inspect, clean or replace faulty expansion valve.

② Excessive air moisture + oversized temperature difference

Reason: Ripening room runs at high RH; large ΔT between air and coil causes heavy condensation & frost.

Solution:

Keep room RH within standard range (85%–90% for banana/avocado).

Operate unit under small temperature difference mode to reduce dehumidification & frost.

Ensure room door is closed tightly to prevent hot humid outdoor air ingress.

③ Insufficient air volume / Blocked air path

Reason: Dirty fins, blocked coil, fan malfunction, blocked air circulation.

Solution:

Clean coil fins, remove dust, debris and residual frost.

Check fan motor, blade and wiring; repair or replace damaged fans.

Clear obstacles inside the room to guarantee smooth air circulation.

④ Defrost system failure

Reason: Defrost timer, heater, sensor or hot gas defrost control broken; defrost cycle too short.

Solution:

Test defrost timer, temperature sensor and electric heaters.

Reset defrost interval & duration properly.

Manually run forced defrost to melt existing ice completely.

⑤ Poor drainage system

Reason: Drain pipe blocked, drain pan clogged, slope not enough. Standing water re-freezes on coil.

Solution:

Clean drain pan and drain line thoroughly.

Check drain pipe slope; ensure smooth water outflow.

Add drain line heat trace if working in low ambient.

⑥ Overloading & improper product stacking

Reason: Too many fruits stacked; goods block air inlet/outlet.

Solution:

Control loading capacity as per room specification.

Leave gaps between fruit stacks for air flow.

3. Step-by-Step Emergency Operation

Turn off cooling system first, run manual defrost until all ice melts.

Clean coil, fins and drainage system.

Check fan running status and air circulation.

Verify refrigerant pressure and charge.

Reset temperature, humidity and defrost parameters.

Restart unit and monitor coil status continuously for 2–4 hours.

4. Preventive Maintenance Tips

Clean evaporator coil and drain system regularly.

Inspect defrost components monthly.

Avoid frequent opening of ripening room doors.

Keep temperature & RH always within rated working range.

Schedule routine inspection for refrigerant and valves.