Reefer containers power requirement, venting heat & recording of information



Container ship at anchor
Fig:Container ship at anchor

Power requirement

Each reefer container is estimated to consume power of 5 KW and the ship's main power supply should be designed to cope with the extra load of running its maximum capacity of reefer containers, although if necessary an additional generator can be installed onboard the ship.

Power shutdowns should be kept to a minimum. All power shutdowns and breakdowns should be diligently logged in order to correspond with the records of the electronic datacorder. It is important that the chilled cargo containers are reconnected as soon as possible after any power loss.

If cargo damage is suspected, inform the company and attempt to salvage the maximum amount of cargo possible by transferring it into an empty but functioning reefer.

At the end of the voyage, disconnect the power from the loaded reefers just before their discharge from the ship. Keep the power supply on as long as practicable. Keep copies of the Partlow charts if they were changed during the voyage. Ensure that documentation is properly completed.

Venting heat

Reefer containers inside the cargo hold expel heat from the air cooled condensers when they are running. This hot air must be vented outside the hold or it will accumulate and the refrigeration machinery will not work efficiently. The blower capacity should provide sufficient air exchange to remove the heat extracted.

If water cooled condensers are used there is a water circulation system of pipes installed in the cargo hold that can be connected to individual reefer containers. These containers are often marked `In Hatch Stowage Allowed'. To determine whether a particular reefer container is suitable for stowage inside the cargo hatch, simply check the water cooled condenser inlet and outlet water pipe connection couplings.

Safety guidelines

1. Monitor personal safety when working:
  • On high tier reefers
  • during rough weather and rain
  • with controlled atmosphere (CA) reefers.

2. While operating valves on refrigerated machinery (or any pressurised machinery) it is important not work directly in front of certain parts and to be aware that the valve spindle or other parts can fly off at high speed. Many serious accidents have been reported from the valve spindle accidentally flying off from the valve housing.

3. Refrigerants may cause frostbite and asphyxiation. It is important to keep away from any leaks. Refrigerants at high temperature can release phosgene which is a highly noxious gas. When they come into contact with moisture they can also form hydrofluoric acid, which is highly toxic, corrosive and attacks metals. Death can result from exposure to hydrofluoric acid rather than just damage to skin and eyes.

Recording of Information and Discrepancies

If there are any differences between the container settings received and the bill of lading instructions, these should be reported immediately. Reefer units should be inspected at intervals not exceeding six hours when at sea. The times of the inspections and details of any problems should be recorded in an appropriate logbook.

There are many situations where the temperature tracking pattern may be misleading and not be a precise representation of the temperature or condition of the cargo. Conclusions should not automatically be made from this temperature information alone. For example:

1. Cargo should be loaded at the carriage temperature stipulated by the shippers. However, if a container is loaded with a cargo where the pulp temperature exceeds this temperature, the (warm) cargo will cause the temperature of the delivery air to rise rapidly when passing around the cargo.

Eventually, the return air may reach a temperature where the refrigeration machinery cannot cool it down sufficiently prior to re-circulating it as delivery air. The tracking pattern on the chart or logger will show a temperature higher than the set-point.

In most cases the difference in temperature between the delivery and return air will narrow as the continuous circulation of air cooler than the cargo brings the cargo temperature down towards the set-point level.

2. If a refrigeration unit ceases to operate, the chart or logger will register a gradual but steady rise in temperature to the point where the ambient temperature is recorded. The sensor will record the air temperature and the record will not then accurately reflect the true position regarding the cargo itself. The cargo will be reasonably well protected from the influences of the external air temperature by the surrounding insulation.

3. The return air temperature sensor is positioned close to to the refrigeration machinery and the temperature record will register some increase during defrosting. These increases, which are noticeable on paper chart recorders, do not have an immediate effect on the actual temperature of the cargo and do not indicate an unstable refrigeration unit. Electronic loggers usually indicate the timing and lengths of defrost periods in addition to temperatures.

If erratically functioning reefer machinery cannot be fixed during the sea transit, the vessel should advise its owners and agents at the next port prior to their arrival so that arrangements can be made to correct the problem ashore. In these circumstances a Surveyor should be appointed to attend the vessel on arrival in order to inspect and report on the condition of the cargo and container.

If a container sustains any physical damage the agent and/or the surveyor must ensure that action is taken to rectify the problem as quickly as possible so as to minimise potential cargo loss.

Where there is a discrepancy in the temperature on the reefer and in the manifest, the matter must be referred to the company for clarification. Do not make assumptions as either could be incorrect.

Confusion between the temperature units of degrees Celsius or Fahrenheit has lead to much cargo damage. Do not make assumptions, obtain clarification.

Display panel
  1. The `in range' light on the display panel should be illuminated. This shows that the air temperature at the controlling probe (irrespective of whether it is chilled cargo or frozen cargo) is satisfactory and within limits. In certain circumstances such as defrosting, this `in range' light may not be lit continuously. However, when the unit returns to its normal cooling mode of operation, and settles down to a stable operation, the `in range' light should be illuminated


  2. if the red light indicating a critical alarm is lit, it requires immediate investigation and the necessary corrective action


  3. earlier models used LED temperature displays that could be seen from a distance. Unfortunately, most units now have LCD displays that are difficult to read from a distance.
Most units have a critical alarm signal (LED) which when lit, needs immediate attention and investigation.

If damage or a loss of quality in the cargo is detected at the end of a trip, the record of the temperature maintained inside the container and the performance record of the reefer machinery will be examined to establish the cause and the extent of the damage and to identify the responsible party. The record of temperature maintenance is called for by the courts in order to determine the integrity of a cargo damage claim.





Our detail pages contain many topics related with refrigeration process of various commodities and prepare for shipment , maintaining temperature in reefer containers ,troubleshooting etc.

  1. Precautions when working in refrigerated spaces


  2. How to change-over of refrigerants of a reefer container ?


  3. How to maintain compressor oil level of a reefer container ?


  4. Function of refrigerant receiver & where it is located?


  5. Maintenance requirement of condenser of a reefer container


  6. Reson of compressor failure and troubleshooting


  7. Maintenance of evaporator coil - how to replace the evaporator fan ?


  8. Maintenance of expansion valve


  9. Inspection of reefer components







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All information contained in this website is for preliminary information only and is not legally binding. The publisher of this website cannot take responsibility for any damage to your reefer cargo due inadequate data or errors. For any remarks please Contact us
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Reefer cargo
Why refrigerate?
We choose to refrigerate commodities such as fruits and vegetables because we want to prolong their “practical shelf life” – the time from harvest until the product loses its commercial value.



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