| Written by Mark Buzinkay

If you manage reefers, you're probably always looking for ways to optimise your reefer fleet's energy usage. One way to do this is by monitoring the reefers' power consumption. Keep reading to learn about reefer containers, how they work, and their power specifications.
Reefer plugs

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Reefer containers are specially designed to transport perishable items that require refrigeration. In order to keep the cargo cool, reefer containers are powered by either an electric motor or a diesel engine. They also have a built-in generator to provide the necessary power. By monitoring the reefers' power consumption, you can get insights into how your reefers are performing and make changes accordingly.

What are some of the benefits of using a reefer management solution?

- Get real-time data on your reefers' power consumption

- Optimise your reefer fleet's energy usage

- Reduce operating costs


If you're interested in reducing your reefer fleet's operating costs, then a reefer management solution is worth considering.


What are reefers used for?

A refrigerated container (reefer) is a shipping container used in intermodal freight transport. Reefer cargo is temperature-sensitive, perishable cargo such as fruits, vegetables, meat, and other items.

Standard reefer containers must be plugged into a power source in order to function. They are usually powered by a generator (reefer genset) attached to the container and provide electricity to the Cooling Unit. These generators can be either fuel-powered or electric-powered, or both. In addition, some reefer containers have a secondary generator set to act as a backup in case the primary fails.

If you're in charge of reefer containers, you must know about the gensets that power them. A genset, short for a generator set, is a power unit that provides electricity to reefer containers. Without a genset, a reefer container cannot cool itself, which is why they are necessary for standard reefer containers worldwide.

Genset controllers are used to monitor and control a genset system's function. A suitable genset controller will provide various monitoring functions of the reefer container, including voltage, current, frequency, and power. It should also be able to measure temperature and oil levels or pressure.

Therefore, it's vital that reefer container insulation can maintain internal cargo temperatures within 1-2 degrees Celsius of the cargo protocol temperature, even with power disconnection periods of 1 to 6 hours during transport. Learn here more about a reefer container temperature monitoring system.


What is a reefer plug?

Reefer container power supply is crucial to keep a certain temperature range. Learn in this section about requirements, specifications, voltage and sockets!

When a reefer is kept at a terminal, it must be plugged into a specialised electrical power outlet of 32 amperes and 380/440 volts. To provide power, terminals install what is known as reefer plugs (sockets) within their yards, which are combined into outlets supplying several reefers.

The reefer container power requirements consist of a three-phase electrical system with a supply voltage of 440/460 volt. Some units are available with three-phase 208/230-volt transformers. Units are available to run on 50 or 60 Hz.

Therefore, all refrigerated containers have a standardised plug attached to a several meters long cable to the genset. The plug is designed for 32amp 440V 60Hz with 4 pins: 3 poles + earth. The earth contact is in the 3-hour earth clocking position. Dockers will take the power cable out of a small box in the front of the reefer and connect the plug with the socket.

Container plugs and connectors need a heavy-duty design for harsh marine environments, a watertight seal, a universal grommet and high resistance to chemicals & impact. Therefore, plugs may have a different look and external features for extra safety, protection and quality, but they have the exact specifications.


Reefer Outlets in Ports

Container Port Terminals are dynamic, harsh and dangerous environments. Reefers need to be connected to power during their stay. Reefer Outlet Assemblies (ROA) are designed to focus on operator safety and are fabricated to withstand marine environments while providing equipment protection. Such ROAs are equipped with safety-interlocked power modules for safe and reliable connections to refrigerated containers. These modules should allow for easy maintenance and minimal downtime.

Safety-interlocked power modules must protect the operator with a "de-energised" circuit during the insertion and retraction of the male plug, preventing making or breaking under load. Terminal installations may also supply moulded-case circuit breakers with various trip ratings to allow for branch, overload and short-circuit protection.

Your standard reefer container will use approximately 18 amps on start-up and continue to use 8 amps while running. Therefore, it's essential to hose down or air-clean the condenser every month to ensure its fins are clean.

Learn more about the development of sustainable ports.


How are reefer containers powered during transport?

When shipping, reefer container operation is typically run on a vessel or shore power. A generator provides portable power to reefers during rail or truck shipping. Containers may have a built-in generator, or they may have one externally located.

Reefer outlets for trains should handle the transportation hazards associated with railroad cargo transport. Therefore, power modules require protection from corrosion and abuse because of the constant vibrations and extreme climatic conditions.

When on a vessel, reefer container sockets are made to withstand harsh marine environments. In addition to standard features of reefer outlets, shipboard reefer sockets require a water protection (IP67) screw cover to ensure a watertight seal. In addition, stainless steel frames, impact-resistant non-metallic sockets, nickel-plated brass contacts, and other stainless steel hardware is beneficial to mitigate corrosion damage. 

Special care must be taken when handling high voltage current in order not to endanger the health of people in the vicinity. In addition, the correct position of the earth contact, the so-called o' clock position, must ensure that machines are not connected to a power supply with too high a voltage and thus overloaded. 



Reefer plugs are an integral part of reefer container technology. By understanding the specifications of reefer plugs and sockets and how they are used, you can ensure that your reefer containers are adequately powered and able to maintain the correct temperature for your products. However, it is not only important to secure the power supply for your reefer genset but also to monitor energy consumption. High energy consumption may indicate a faulty system, bad isolation, improper stowage or outdated genset technology (further reading: Reefer container). 

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