Reefer Container Monitoring

What sets reefer monitoring apart

Each reefer container carries its own self-contained refrigeration unit with its own compressor, controller and setpoint; the ship does not refrigerate the cargo, it only supplies power and, where fitted, monitors what the container's own controller is reporting. Reefer monitoring systems read data such as supply current, return air temperature, setpoint and active alarms from every plugged socket and present it on a central display, so a fault in one box among hundreds is flagged instead of relying on a physical round of the stacks. Some systems only report an alarm; more capable ones log temperature history for the whole voyage, which becomes evidence if a claim is made on the cargo.

Main components

Reefer sockets and plugs

Standard 3-phase power outlets at each reefer stow position, typically 440 V or 460 V depending on trade, wired back to distribution panels dedicated to reefer load.

Monitoring interface unit

A reader at or near each socket, or a data connection through the container's own PLC where the reefer supports remote monitoring, converting the container's status data into a signal the ship's system can use.

Data bus and central controller

A shipwide network, often a dedicated bus separate from the main automation system, aggregating every monitored position into one central unit.

Bridge or cargo office display

Software presenting stow position, setpoint, actual temperature and alarm status per container, usually with the ability to log and export data for the whole voyage.

Selection and sizing

• Number of reefer plugs the system must cover against total reefer stow capacity, including any future increase
• Compatibility with the range of reefer container makes expected in service, since older units may lack a data interface and only support current monitoring, not full data readout
• Data logging depth and export format required by the operator's cargo claims process
• Integration with the ship's power management system, since reefer load is a major and variable part of total electrical demand and step loads on start-up matter for generator loading

Regulations and class

There is no SOLAS chapter dedicated to reefer monitoring itself, but class societies offer optional notations for reefer container capability that require a working monitoring and alarm system as part of the class scope, and cargo insurers and major reefer cargo shippers increasingly expect temperature logging as standard practice for claims purposes. Electrical distribution to reefer sockets falls under the same class rules as any other power distribution circuit, including protection coordination and cable sizing for the connected load.

Typical faults

What to look for in a supplier

• Confirmed interface compatibility with the reefer container brands the operator's trade actually uses, not a generic claim of universal compatibility
• Data export in a format accepted by the operator's cargo claims and P&I correspondents
• Alarm escalation logic that distinguishes a real temperature excursion from a brief data dropout
• Spares holding for interface units, since a failed unit at one socket takes that stow position out of monitored service until replaced

Treat a gap in the logged data the same as a temperature alarm until proven otherwise — an unmonitored reefer for part of the voyage is exactly the stretch a cargo claim will focus on.