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REFRIGERATION

Troubleshooting

High-temperature alarm going off

A high-temperature alarm means the cabinet sensor has been above the alarm limit for longer than the programmed delay. That delay exists so that a door opening or a normal defrost does not set it off. When it does sound, something has kept the cabinet warm for a meaningful time. The causes range from a door left ajar overnight to a failed compressor. Your first job is the food, the second is the cause. Do not just silence the buzzer and walk away: the alarm will often stop on its own while the underlying fault is still there, and the next time it may be too late for the stock.

First, check these

  1. Read product temperature with a probe thermometer, not just the display. Chilled food should be at or below 5 °C and frozen food at or below −18 °C.
  2. Check that the door or lid is fully closed and nothing is wedging it open. Look for a door left ajar during cleaning or restocking.
  3. Check whether the unit has just come back from a power cut, a long defrost or a large delivery.
  4. Look and listen: is the compressor running, is the condenser fan turning, is air coming from the evaporator fan inside?
  5. If product is already above safe limits or rising, move high-risk items to another cold unit now.

Likely causes

  1. 1. Door left open or not sealing

    You can check this

    Signs: Door found ajar, gasket torn or folded, frost along the door edge, alarm during cleaning or restocking.

    Fix: Close the door and check the seal. The cabinet should recover within an hour or two if nothing else is wrong. Replace or reseat a damaged gasket.

  2. 2. Warm product loaded

    You can check this

    Signs: Alarm shortly after loading cooked food, a delivery from an un-chilled vehicle, or many bottles at room temperature.

    Fix: Give the unit time to recover with the door shut, and in future cool food first and load in smaller batches.

  3. 3. Recovery after a power cut

    You can check this

    Signs: Alarm appears when power returns; the controller may show a power-failure code.

    Fix: Check that the compressor restarts after any built-in delay and record how long the outage lasted. Then judge the food as described in our power-cut guide.

  4. 4. Blocked condenser or failed condenser fan

    You can check this

    Signs: Hot air around the machine compartment, compressor tripping on and off, alarm on hot afternoons.

    Fix: Isolate power and clean the condenser. If the condenser fan is not turning, keep the unit off and call a technician.

  5. 5. Iced evaporator or failed evaporator fan

    Technician job

    Signs: Solid ice on the coil inside, little or no air from the fan outlet.

    Fix: Move stock and do a manual defrost as a stopgap; a technician needs to repair the defrost system or fan.

  6. 6. Refrigeration fault such as leak or compressor failure

    Technician job

    Signs: Compressor not running, or running constantly without cooling; temperature still rising with the door closed and condenser clean.

    Fix: Call a technician and move stock. This needs diagnosis and sealed-system work.

  7. 7. Alarm settings or sensor fault

    Technician job

    Signs: Alarm sounds while your checked thermometer shows correct temperatures, or the display reads erratically.

    Fix: A technician should check the probe and the alarm limit and delay settings.

When to call a technician

Call a technician if the cabinet does not start recovering within an hour with the door shut and a clean condenser, if the compressor or a fan is not running, if the alarm repeats day after day, or if the sensor seems wrong. Record the alarm time, the product temperatures you measured and what you did with the stock; your food-safety records need this too.

Isolate power before cleaning condensers or defrosting. Do not open electrical enclosures. Sealed-system repairs, particularly on hydrocarbon (R290 or R600a) units, must be done by trained technicians.

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