Reefer Plugs: IEC 60309 32 A 3h Explained

The IEC 60309 plug family in brief

IEC 60309 is the international standard for industrial plugs, socket-outlets and couplers, often called "CEE" or "pin and sleeve" connectors. Three things identify a device in the family:

Current rating, such as 16 A, 32 A, 63 A and 125 A, which sets the body and pin size.
Pole configuration, such as 2P+E (single phase) or 3P+E (three phase, four pins).
Voltage and frequency, shown by the housing color and by the clock position of the earth contact relative to a keyway. Red housings cover the 380 to 480 V range.

The clock position is the mechanical key. Two plugs with the same color and rating but a different earth position will not mate, which prevents a device rated for one supply being plugged into another.

Why reefer plugs are "3h"

Most red 3P+E devices you meet on land are 6h, the position IEC 60309-2 assigns to 380–415 V, 50/60 Hz supplies. Reefer plugs use the 3h position. In the clock-position table reproduced by plug maker Mennekes from IEC 60309-2:2023, the 3h position for 3P+E devices is marked as being only for refrigerated containers (ISO standard), for supplies in the 220/380 to 250/440 V range at 50/60 Hz.

3P+E device (red, 32 A)	Earth position	Typical use
Standard 400 V industrial	6h	Workshops, site supplies, most land-side three-phase equipment
Reefer container	3h	Refrigerated container power leads, and the matching receptacles on ships, terminal racks, gensets and depot supplies

Reefer plugs and sockets are widely sold as 32 A, 3P+E (four pins), 380–440 V, 3h, red, and in watertight IP67 versions for exposed use. The practical rule: a reefer lead needs a 3h plug, and a reefer supply needs 3h receptacles. A 6h device from a general electrical wholesaler will not mate, and forcing an adapter into the chain removes the protection the keying gives you.

As always, confirm the details against the refrigeration unit maker's documentation and the receptacles at the terminals and on the vessels you use.

Where reefer plugs connect

Ships, through reefer sockets in the holds and on deck.
Terminal reefer racks and plug-in areas.
Generator sets for road and rail movements. Clip-on gensets hang on the front of the container; undermount gensets are fitted under the chassis. Either way, the reefer's lead plugs into the genset's receptacle.
Depot and cold-store supplies, which are fixed electrical installations and belong with a qualified electrician working to local regulations.

Gensets commonly deliver 460 V at 60 Hz for the reefer, according to chassis builder CIE Manufacturing's description of how gensets connect. Genset makers' own documentation governs the receptacle and wiring on the genset side.

Choosing a replacement plug

Check	Why
32 A, 3P+E, red, 3h	Must mate with the reefer receptacles you use
Ingress protection (for example IP67)	Leads lie on wet quays and decks, and plugs are left unplugged
Cable entry range	The gland must seal on the actual outside diameter of your lead
Conductor terminal range	Terminals must suit the conductor cross-section
Housing material	Impact resistance and cold performance for dropped plugs
Strain relief	Leads are pulled by the cable more often than they should be

Plugs, connectors and receptacles: the terms

IEC 60309 uses precise names for each part, and suppliers' catalogs follow them:

Plug: the male part on the end of the reefer lead.
Socket-outlet (often called a receptacle in North America): the fixed female part on a rack, ship bulkhead or genset.
Connector: a female part on the end of a cable, used to build an extension lead.
Appliance inlet: a male part fixed to equipment.
Interlocked socket-outlet: a socket with a switch that cannot be turned on until a plug is inserted, and prevents the plug being withdrawn while live.

When you order, name the part type as well as the rating and clock position.

Fitting a plug correctly

Prepare the cable to the plug maker's strip lengths, so the gland clamps the sheath, not the cores.
Terminate phases and earth to the marked terminals, with ferrules if the maker calls for them.
Where the maker's instructions call for it, leave the earth conductor slightly longer than the phases, so it is the last to pull free.
Tighten terminals and gland to the specified torque.
Test earth continuity, insulation resistance and phase order before the lead returns to service. Phase order matters, because a reversed rotation affects the refrigeration unit.

Plug fitting on reefer leads is electrical work. Follow your local rules on who may do it and how it is tested.

Common questions

Is a reefer plug the same as a standard red 32 A plug?

No. Both are red, 32 A, 3P+E, but a standard land-side plug normally has its earth at 6h and a reefer plug at 3h, so they do not mate.

What voltage do reefer containers use?

Reefer units run on three-phase AC. Supplies of 380–460 V are common, and gensets commonly supply 460 V at 60 Hz. The unit maker's documentation states what a particular unit accepts.

Can I use a 6h-to-3h adapter?

An adapter defeats the keying that stops a device being plugged into the wrong supply. Use 3h receptacles where reefers are powered, and have any installation designed by a qualified electrician.

Why do reefer plugs fail?

They are dropped, dragged, run over and left open to the weather. Cracked housings, bent pins and water in the plug are the common faults. See reefer container power cables for the lead itself.

What to send a supplier

Plug: IEC 60309, 32 A, 3P+E, red, 3h, IP rating, housing material.
Cable: type, conductor cross-section, outside diameter and length.
Unit-end termination as the refrigeration unit maker specifies.
Tests: earth continuity, insulation resistance and phase order on every lead.

Material choices for leads that live outdoors are covered in cable jacket materials.