Common cold storage errors and effective solutions

An industrial cold store runs 24/7, and any fault lasting more than 4 hours can spoil goods worth billions of dong. Across more than 20 years designing and installing refrigeration systems directly for large seafood, food and pharmaceutical businesses such as NECS and AJ Total, Tân Long's engineering team has assembled this set of remedies for common errors of cold storage to help businesses reduce operational risk.

This article classifies 17 fault groups across 5 main systems, from the compressor package through to PLC automation equipment. We give specific measurable thresholds for pressure, temperature and current, together with a diagnostic priority sequence based on the standards of major manufacturers such as Mycom and Bitzer. You will also find an urgency classification table showing which faults require an immediate shutdown, and the preventive maintenance steps that keep them from recurring.

In day-to-day operation, quickly identifying common errors of cold storage is critical to protecting product quality. At Tân Long we classify 17 technical fault groups into 3 priority levels based on the damage risk to the compressor package and the safety of the system.

To stop common errors of cold storage turning into expensive damage, Tân Long recommends servicing a cold store at least once every 3 months so the system always performs at its best.

Group 1: Refrigerant and pressure system faults

Within the list of common errors of cold storage, refrigerant and pressure faults account for around 40% of all emergency maintenance call-outs at Tân Long. Left unresolved, they lead to serious compressor damage and large-scale product loss.

Refrigerant undercharge (leak)

Cold storage undercharge usually shows up as suction pressure below the safe operating threshold (typically 65 to 75 psi for R404A at an evaporating temperature of -30°C). When this happens, the room temperature climbs steadily even though the system keeps running.

• Common leak points: Pipe welds, connections on the throttle valve, solenoid valves and gate valve seals are the weakest points in the system.
• Standard technical procedure:
  • Use a manifold gauge set to establish suction and discharge pressure precisely.
  • Use an electronic leak detector to find the leak before topping up the refrigerant charge.
  • Evacuate the whole system for at least 30 minutes to reach a pressure of -1 bar before returning it to service.
• NH3 system safety warning: In ammonia systems, concentrations above 300 ppm cause severe respiratory irritation. Technicians must wear respiratory protection when dealing with a leak.

Abnormally high discharge (head) pressure

This is one of common errors of cold storage causes the high pressure switch to trip and stop the compressor. The safe design threshold is typically below 24 bar for R404A.

• Reason: 55% of cases come from a evaporative condenser that is too dirty to reject heat effectively. An overcharge of refrigerant, or an ambient temperature above 40°C , are the other main causes.
• Consequences: Running at high pressure over a long period raises power costs by 15% to 25% and cuts equipment life by 40%. Tân Long strongly advises against bypassing this protection device.

Compressor liquid flooding

Liquid flooding is the fastest way to destroy a compressor. When liquid refrigerant reaches the compressor cylinder through the suction line, the sudden hydraulic force breaks the connecting rod, cracks the cylinder or wrecks the valves instantly. Replacing an industrial screw compressor costs between 50 and 200 million dong (roughly USD 2,000-8,000) depending on capacity.

Liquid flooding is recognised by a sudden metallic knocking from the compressor, together with a sharp rise in suction pressure and an abnormally low discharge temperature. Shut down as soon as you hear metallic knocking — do not wait for the protection system to trip.

Group 2: Compressor and power system faults

Refrigeration compressor is the heart of any industrial refrigeration system. In the list of common errors of cold storage, compressor faults always rank as the most serious, because they directly affect the ability to hold temperature and carry the highest replacement and repair cost.

Compressor will not start

When the compressor will not start, the system stops producing cooling altogether, putting the stored goods directly at risk. This is one of the common errors of cold storage relating to the control system and the electrical supply.

• Technical diagnostic procedure:
  • Check the supply: Confirm the indicator lights on the control cabinet are lit, and check that no breaker has tripped and no fuse has blown.
  • Measure the voltage: Check the incoming voltage at the compressor contactor; it must read 380V ±10% for a three-phase supply.
  • Check the signal: Establish whether the start command from the thermostat or the PLC control + SCADA has actually been sent.
• Common causes: If the signal is present but the contactor does not pull in, the fault usually lies in an open contactor coil or a voltage drop. If the contactor has closed but the compressor stays silent, measure the motor winding resistances to determine whether a winding has burnt out.

Compressor short-cycling (running and stopping repeatedly)

A compressor that starts and then stops after a few minutes (under 5 minutes) indicates that thermal protection devices such as the overload relay are operating to prevent worse damage. This is a priority fault in the list of common errors of cold storage at industrial sites.

• Reason: It is usually caused by a dirty condenser reducing heat-transfer efficiency, an ambient temperature above the design threshold, or an unstable mains supply.
• Note: Never reset the protection repeatedly before the root cause is found — doing so can burn out the compressor motor completely.

Abnormal noise from the compressor

Listening to and classifying unusual noises lets store operators quickly diagnose common errors of cold storage without dismantling any equipment.

Group 3: Temperature and evaporator operating faults

Temperature faults rarely cause a sudden shutdown, but they do cause significant cumulative damage. They are among the common errors of cold storage that slowly degrade stored goods, drive power consumption up sharply and seriously shorten the life of the system.

The cold store not reaching setpoint

When the store runs continuously but temperature will not come down to design, technicians should work through the common causes in the list of common errors of cold storage hereafter:

• Refrigerant undercharge: Suction pressure falls below the safe threshold (under 65 psi / 4.5 bar).
• Poor heat transfer: Industrial Air Cooler heavy frost reduces the contact area, cutting actual capacity by 30% to 60% against the original design.
• Heat loss: Warm air entering through damaged door seals or gaps in the cold store panel envelope.
• Product overload: More goods received than the system was sized for.
• Inspection procedure: Measure the air temperature difference across the evaporator (the standard range is 8°C to 12°C), and inspect how well the doors seal.

Heavy frost build-up on the evaporator

Frost packing the evaporator solid is the result of a defrost cycle that is not working correctly or not running long enough. This fault can wipe out as much as 80% of the store's cooling capacity.

• Technical causes: A faulty defrost timer or defrost heater element.
• Standard operating parameters: For the cold storage sub-zero temperature (from -18°C to -25°C), the standard defrost cycle is typically 2 to 4 times a day, each lasting 20 to 30 minutes.
• Solution: Check the automation control system regularly to make sure defrosting clears the ice completely.

Store temperature too low (overcooling)

A store colder than its setpoint is usually caused by a failed thermostat or a sensor sending an incorrect signal. This is the single biggest source of wasted power among common errors of cold storage.

• Symptoms: The thermostat does not send the stop command to the compressor when the target temperature is reached, so the machine runs without a break.
• Remedy: Check continuity of the sensor and its signal wiring. Reset the parameters on the control panel according to the standard temperature table for the specific product being stored.

To keep the system performing at its best, schedule regular maintenance and warranty inspections so latent failure risks are caught early.

Group 4: Cold store structural faults

Structural faults usually develop quietly over time. By the time the signs are obvious, though, they are very expensive to fix — sometimes requiring the whole system to be taken out of service for an overhaul. This is a particularly serious group among common errors of cold storage that owners need to watch.

Floor heave from ground freezing

Floor heave occurs when cold passes through the floor insulation into the ground, freezing the water in the soil. Over the years the accumulated ice exerts enormous upward force, deforming and breaking up the floor structure. Among common errors of cold storage, this is one of the hardest to fix quickly: the store must be taken out of service completely to thaw the ground (3-7 days), the floor panels lifted, the underfloor ventilation system repaired, and everything rebuilt.

Repair costs run from 15-40 million dong (roughly USD 600-1,600) depending on floor area. Prevent it by designing an underfloor ventilation system of 100 mm (4 inch) PVC ducts laid in a zigzag at 60-80 cm spacing, vented to open air at both ends — applied from the construction stage onwards.

Air infiltration into the cold room

In high-humidity regions such as Ho Chi Minh City, warm outside air constantly infiltrates the cold room through gaps. This is one of the common errors of cold storage that causes frost build-up on the evaporator and raises power consumption.

• Reason: It usually results from damaged door seals or insulated panels that have not been fitted tightly.
• How to fix:
  • Inspect door seals every 3 months.
  • Use dedicated T-Light insulated doors with magnetic seals for a completely airtight closure.
  • On larger systems, add PVC strip curtains or design an air lock at the loading door area to minimise heat loss.

Moisture vapour migration through the insulated panel

The vapour pressure difference between the inside of the cold store (low, because the temperature is low) and the outside (high) drives a continuous migration of moisture through the panel. The polyurethane core gradually becomes damp, degrading its insulating value (thermal conductivity rising from an initial 0.022 W/mK to 0.035-0.05 W/mK after 5-10 years). Badly affected panels have to be replaced, because their insulating performance cannot be recovered.

Choosing a contractor with a proven project record, such as Tân Long, minimises common errors of cold storage related to the building fabric right from the outset.

Group 5: Electrical and control system faults

Electrical and control faults usually result in a sudden shutdown, putting stored goods at high risk. This is the most complex group among common errors of cold storage because the technician must separate power-side faults clearly from digital control faults.

Compressor and fans stop together

When the compressor, evaporator fans and condenser fans all stop at the same time, the system has gone into emergency shutdown. Among common errors of cold storage, this usually has two main causes:

• Loss of the main supply: Check the main breaker and the branch breakers in the power panel immediately to establish whether anything has tripped on overload or short circuit.
• Emergency stop signal from the controller: The central controller issues a stop command to protect the system when it detects an abnormal parameter. The advantage of a system installed by Tân Long is the use of PLC and SCADA control, which logs fault codes and the exact time of the event, so technicians can diagnose quickly without a manual search.

Failed control board and thermostat

The control board and thermostat are the brain that coordinates the whole refrigeration cycle. A failure here is among the common errors of cold storage that appear after long service or environmental exposure.

• Control board faults: Usually caused by unstable mains voltage, conducted lightning surges, or moisture penetrating the panel after 8 to 10 years in service.
• Thermostat faults: Traditional mechanical thermostats are prone to a broken capillary or loss of internal pressure, producing a temperature error of 2°C to 3°C. Tân Long recommends replacing them with modern electronic thermostats for high accuracy (an error of only ±0.5°C).

To limit the damage from common errors of cold storage, standard cold stores today all integrate remote monitoring technology. The system logs operation automatically and sends an immediate alert by SMS or email when temperature exceeds the setpoint. That lets the maintenance team respond within the golden window, resolving the fault before the goods begin to deteriorate.

You can also read our company profile page for more on the electrical safety standards Tân Long applies to major projects.

Preventive maintenance schedule for common cold storage faults

Most technical faults can be prevented if a business puts a methodical maintenance programme in place. Tân Long's experience installing and operating more than 200 industrial cold storage facilities shows that sites keeping to a regular maintenance schedule cut unplanned common cold storage faults by 60% to 70%.

Below is the standard technical inspection schedule that keeps performance optimal and extends equipment life:

Letting these intervals slip is the direct cause of common cold storage faults such as a burnt-out compressor, moisture ingress or wholesale product loss.

Tân Long offers scheduled maintenance and warranty packages to HACCP standards, including detailed technical reporting and a commitment to respond within 2 hours in an emergency.

Technical advice: for a maintenance quotation matched to the scale of your system, please call the hotline (+84) 933357058 – Mr. Thinh, or the project engineering team at tanlongvn.com, for a direct site survey.

When should you shut down immediately and call a technician?

In day-to-day operation, spotting common errors of cold storage early is critical to equipment life. Isolate the whole system from the electrical supply immediately and call a technician if you encounter any of the following three critical situations:

• Situation 1: Abnormal metallic knocking from the compressor: Regular metallic knocking from inside the compressor is a warning sign of liquid flooding or mechanical valve damage. Among common errors of cold storage, this is extremely serious. Keep running and the compressor may crack a cylinder, at an estimated cost of 50 to 200 million dong (roughly USD 2,000 to 8,000) depending on machine capacity.
• Situation 2: Refrigerant leak: If you detect a strong pungent smell (in NH3 cold storage systems) or receive a gas concentration alarm from the control panel, evacuate the area immediately. Set up forced ventilation and call a technical team with proper protective equipment to deal with the leak, avoiding any risk of fire, explosion or food contamination.
• Situation 3: Repeated high-pressure trips: If discharge pressure exceeds the high pressure cutout twice or more within an hour, the system is in serious thermal overload. This is one of the common errors of cold storage caused by a dirty evaporative condenser or a failed condenser fan. Trying to restart without dealing with the root cause will burn out the motor windings or rupture the receiver.

Tan Long is committed to helping customers inspect and resolve technical faults quickly. Our core team, with more than 20 years of experience, will give you the most accurate assessment of the condition of your refrigeration equipment.

How does Tân Long handle cold storage faults?

Tân Long Refrigeration Electromechanical Joint Stock Company has operated since 2005 in industrial refrigeration system construction in Vietnam, with an equipment manufacturing plant in Duc Hoa Industrial Park, Tay Ninh. Our technical team is made up of refrigeration and electromechanical engineers with 10 to 25 years of hands-on site experience.

Among our flagship projects, Tân Long designed and built the NH3 refrigeration system for LOTTE F&G Vietnam Co., Ltd (Long Hau Industrial Park, Tay Ninh — formerly Long An), a 12,000 MT cold store for Frescol Tuna Vietnam Co., Ltd (Nghe An), and an NH3 refrigeration system with 8 high-speed IQF lines for Kyokuyo Vina Foods Co., Ltd. Practical experience on large-scale projects across a range of climates is the foundation of the diagnostic approach Tân Long's technical team brings to every maintenance call.

Tân Long holds HACCP certification for its food cold storage design and construction process, and provides consulting, cold storage installation and industrial compressor package services to the Vietnamese and Southeast Asian markets.

Is your cold store in trouble? Tân Long's technical team offers free remote diagnosis within 30 minutes. Call (+84) 933 357 058 (Mr. Thinh) or (+84) 982 330 357 (Mr. Sang) during business hours, Monday to Saturday, 8:00-17:30.

Frequently asked questions about cold storage faults

Why is my cold store not reaching temperature?

A cold store failing to reach its setpoint usually comes down to 5 main causes, in order of frequency: refrigerant undercharge (suction pressure below 65 psi / 4.5 bar), heavy frost on the evaporator blocking heat transfer, warm air entering through a door or damaged panel, a product load beyond design capacity, and a worn compressor running below efficiency. Check system pressures and inspect the evaporator first.

What should you check first when a compressor will not start?

Check the supply to the control panel first (has the main breaker tripped, is the voltage within 380V ±10%?). Then check the control signal from the thermostat or PLC. If the signal is present but the contactor does not pull in, the usual cause is an open contactor coil. Do not keep switching it off and on before the cause has been identified.

Is noise from a cold store compressor dangerous?

Regular metallic knocking in time with compressor speed is the most dangerous sign, indicating liquid flooding or mechanical valve damage. Shut down immediately. Low-frequency noise from a fan or pipework resonance is less dangerous but should be scheduled for early inspection, before bearing wear leads to worse damage.

What are the dangers of an NH3 refrigerant leak in a cold store?

NH3 (ammonia) at concentrations above 300 ppm (0.03%) irritates the respiratory tract and eyes. Above 2,500 ppm it can be fatal. If you detect the characteristic pungent ammonia smell, evacuate the area at once, start forced ventilation, and call a technical team with protective equipment. Never enter the leak area without suitable respiratory protection.

How long does floor heave take to repair, and what does it cost?

Repairing floor heave requires the store to be taken out of service completely. The process involves thawing the floor (3-7 days depending on area), lifting the floor panels, drying out the ground, rebuilding the PVC underfloor ventilation system, and refitting the panels. Total time is typically 10-21 days. Cost runs from 15-40 million dong (USD 600-1,600) for a small to medium store.

How often should a cold store be serviced?

Weekly, check operating pressures and temperatures. Monthly, clean the condenser and evaporator. Quarterly, change the oil filter, measure insulation resistance and check refrigerant moisture content. Annually, overhaul the whole system including a tightness test and a compressor oil change. Customers who keep to this schedule see 60-70% fewer unplanned faults.

What should you do with a cold store during a sudden power cut?

Close all store doors immediately to hold the cold in. A sealed freezer store (-18°C / 0°F) can hold a safe temperature for 4-6 hours depending on panel thickness. When power returns, start equipment one item at a time, 5-10 minutes apart, to avoid overloading the supply with simultaneous starting currents. Watch pressures and temperatures for the first 30 minutes after restart.

Can you keep running with high discharge pressure?

You should not. Discharge pressure above the design threshold raises power consumption by 15-25% and shortens compressor life considerably. If the high pressure switch trips twice or more within an hour, shut the system down and deal with the cause (usually cleaning the condenser or correcting the refrigerant charge) before returning it to service.

What is compressor liquid flooding and how should it be handled?

Liquid flooding is when liquid refrigerant reaches the compressor cylinder. Liquid cannot be compressed, so it creates a sudden hydraulic force that breaks the connecting rod or cracks the cylinder. It is recognised by sudden metallic knocking from the compressor. Shut down immediately. Do not restart until a technician has checked and confirmed that the expansion valve is working correctly and there is no liquid left in the suction line.

What does industrial cold storage repair usually cost?

Costs by item: topping up refrigerant 2-5 million dong (USD 80-200), replacing a contactor or thermostat 1-3 million dong, cleaning the condenser and evaporator 2-6 million dong, replacing an industrial compressor 30-200 million dong depending on capacity. A scheduled maintenance contract with a professional contractor typically saves 50-70% against the cost of emergency repairs plus product losses.