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REFRIGERATION

Troubleshooting

Display case glass fogging up

A refrigerated display case is a balance between keeping food cold and keeping the glass clear. Cold air circulates over the product, and the glass sits between that cold air and a warm, often humid shop. If the glass drops below the dew point of the room, it fogs. Cases manage this with double glazing, airflow along the glass and, in many models, heated or coated glass. Fogging starts when room conditions exceed what the case was designed for or when those features are disturbed. Fans, AC outlets and open shopfronts, all common in Indian bakeries and sweet shops, are the usual triggers. Clear glass also matters for food safety: staff who cannot see the product open the case more often, which warms it further.

First, check these

  1. Check which side of the glass is fogged: customer side (outside) or product side (inside).
  2. Look for a ceiling fan, pedestal fan or AC outlet blowing onto the case. Moving air disrupts the case's air pattern.
  3. Check rear doors or sliding panels are closed and staff are not leaving them open during service.
  4. Check product is not stacked above the load line or pressed against the glass, blocking the air circulation.
  5. Check that any glass heater or anti-mist switch is on.
  6. Check the case setpoint has not been lowered. Colder glass fogs more easily without making the food any safer.

Likely causes

  1. 1. Room humidity beyond design

    You can check this

    Signs: Outside fogging on humid days or near the entrance; clears in drier weather or when the AC runs.

    Fix: Keep the shop door closed where AC is used, move the case away from the entrance, and control room humidity. Wipe with a dry, lint-free cloth.

  2. 2. Fan or AC draught on the case

    You can check this

    Signs: Fog in a patch facing a fan or AC outlet; cold air spilling from the case.

    Fix: Redirect fans and AC louvres away from the case, or relocate the case.

  3. 3. Rear doors left open

    You can check this

    Signs: Inside fogging during service; warm air from the back counter entering the case.

    Fix: Train staff to close rear doors after each serve and use night covers or blinds after hours.

  4. 4. Overloading or warm product

    You can check this

    Signs: Trays above the load line, fresh-baked or still-warm items placed in the case, steam visible on loading.

    Fix: Load below the marked line and allow baked or cooked items to cool before display.

  5. 5. Glass heater or anti-mist feature failed

    Technician job

    Signs: Glass much colder than usual; fog appeared suddenly though conditions have not changed.

    Fix: A technician should test the heater circuit and controls.

  6. 6. Iced evaporator or fan fault

    Technician job

    Signs: Weak airflow inside, rising product temperature as well as fogging.

    Fix: A technician should check the defrost system and evaporator fans.

When to call a technician

Call a technician if fogging continues after you have dealt with draughts, rear doors and loading, if the glass heater seems dead, or if product temperatures are also rising. Fog between double-glazing panes means a failed glass seal and needs a glass replacement.

Isolate power before cleaning glass heaters, light rails or the inside of the case. Use cleaners suitable for coated glass and avoid spraying liquid onto electrical parts. Hydrocarbon refrigerant (R290 or R600a) units need trained technicians for any refrigeration work.

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