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Air Curtain Insufficient Airflow → 30%+ Cold Air Loss on Door Opening

Likely causes

Partial fan motor failure — one open phase drops RPM, cutting airflow 30–50% from design (1,500–3,000 m³/h)

Check: Measure discharge velocity with anemometer — below 50% of design (4–6 m/s) requires investigation. 3-phase current imbalance >±10% indicates motor replacement

What to do: Replace fan motor. After replacement, verify 3-phase current balance and airflow restored to 4–6 m/s

Air filter blockage — no cleaning for 6+ months reduces airflow 20–40%

Check: Visually inspect filter for dust and fouling. If airflow recovers after cleaning filter, filter was the cause

What to do: Remove and wash filter (aluminum mesh is water-washable) or replace. Set cleaning interval to every 3 months

Belt-drive slip or slack — effective air velocity drops from 4–6 m/s to below 2 m/s

Check: Belt tension check: press center of belt with finger — 10–15 mm deflection is normal; adjust if exceeded

What to do: Readjust belt tension or replace belt. Readjust discharge louver angle to point directly at center of door opening

Field tip

Air curtain velocity below 4 m/s is almost the same as having none. Below 3 m/s — diagnose and repair immediately. Verify effectiveness: measure temperature change at door bottom 30 s after opening — rise >2°C means insufficient barrier.

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