Blast Freezer Food Core Temp Not Reaching -18°C

Question

Accepted Answer

Air blast fan airflow below 3 m/s — belt stretched or fan blade damaged. Check: Measure airflow at 3+ discharge points with anemometer — if below 3 m/s, check belt sag (over 10mm) and blade damage What to do: 1. Replace belt and readjust tension (max 10mm sag)
2. Replace entire fan blade set if damaged (prevent imbalance)
3. After replacement, verify airflow above 6 m/s with anemometer Evaporator coil frost thickness over 5 mm — insufficient defrost cycles (less than 2/day). Check: Check coil frost thickness before blast operation + measure electric defrost heater current (suspect heater break if 20%+ below rated current) What to do: 1. Perform forced defrost: 3kW heat gun or hot water spray for 30~60 min; fan-only natural defrost is prohibited (product loss risk)
2. Increase defrost cycle to 3 times/day
3. If heater element broken, replace and verify rated current restored Trolley loading gaps too narrow — blocking air circulation between products. Check: Directly measure product gaps with ruler → if below 50mm, rearrange. Non-uniform air temperature in chamber (8°C+ deviation between inlet and outlet) is also evidence of insufficient spacing What to do: 1. Rearrange products on trolley to minimum 50mm spacing
2. Mark floor guide lines inside trolley or provide spacing spacers
3. Train operators: explain that insufficient spacing causes core temperature failure Low refrigerant causing low evaporation pressure — suction pressure 20%+ below normal. Check: Check suction pressure gauge → if 20%+ below design, low refrigerant. Review annual charge records What to do: 1. Locate leak with electronic leak detector
2. Repair leak, then recover, evacuate and recharge to design charge amount (±5%)
3. Recheck suction pressure and superheat Blast chamber door seal worn — cold air leakage causing 15~25% capacity loss. Check: With door closed, slip A4 paper at 8 points and pull — if it slips out without resistance, seal replacement needed What to do: 1. Replace worn door seal — ensure at least 5mm seal compression
2. Adjust door hinges and closers to confirm full closure
3. After replacement, repeat 8-point paper test

Blast Freezer Food Core Temp Not Reaching -18°C

Likely causes

Air blast fan airflow below 3 m/s — belt stretched or fan blade damaged

Evaporator coil frost thickness over 5 mm — insufficient defrost cycles (less than 2/day)

Trolley loading gaps too narrow — blocking air circulation between products

Low refrigerant causing low evaporation pressure — suction pressure 20%+ below normal

Blast chamber door seal worn — cold air leakage causing 15~25% capacity loss

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