Safe energy delivery

Consumables

You would not think that a power cable is a particularly interesting topic. However, every reefer unit requires one to operate and it is an item that is under constant abuse through its everyday handling and is therefore replaced frequently in service.

The power cable of a reefer is there to serve one main purpose: to connect the reefer machine to an electrical power source delivering 3 phase, AC power according to ISO specifications. This can be provided by mains power on shore, vessel generated power supply, multi-unit or individual genset.

The cable is constructed with multi-stranded copper conductors for flexibility, each electrically insulated from each other. The 3 conductors and ground wire are then wrapped in a second layer of protective sheaths to provide the abrasion, oil, chemical, water and UV light resistance.

MCI sells the 4×4 mm² cable for use in service as it can be used on all types of reefer machines and is equivalent to 11 AWG.

Safety in focus

A very important quality of the cable insulation and outer sheath is to be flame retardant, so that any break, short or improper splice that results in overheating will not continue to burn once the power outlet circuit breaker has tripped.

Power cable can be sized in either metric or imperial units, however the way these are named and calculated are quite different. The metric system is based on the total cross-sectional area of the copper conductor, stated in mm² while the imperial system generally uses American Wire Gauge, or AWG.

AWG is based on a method of drawing wire through various dies to reduce the diameter, so the greater number of dies, the smaller the wire. Hence AWG numbers increase as the wire size decreases. The AWG cables can be cross referenced to the cross-sectional area using formula and commonly available tables.

The required size of the cable for a reefer container is based on the length of cable (generally 18 m) and the maximum current drawn by the reefer machine. As all reefers are using the 32 amp power outlet, the maximum current draw is 32 amps, so 4×4 mm² cable is most suitable. The closest AWG number to 4 mm² is 11 AWG which is actually 4.17 mm².

Bigger is not always better

The Star Cool unit is designed with the best energy efficiency and lowest power consumption, so that with its maximum 16 amp power draw, it only requires a smaller 2.5 mm² cable which is the original cable used in production. The 2.5 mm² cable cannot be used on other reefer machines which have higher maximum current. Therefore, MCI is only selling the 4×4 mm² cable for use in service as it can be used on all types of reefer machines and is equivalent to 11 AWG.

MCI sells the 4×4 mm² cable for use in service as it can be used on all types of reefer machines and is equivalent to 11 AWG.