Industrial plugs and socket-outlets: reading the colour code, IP rating, number of poles and earth contact position

2. Colour code by voltage

Where the manufacturer uses colour to indicate the operating voltage (in addition to the text marking), the colours are specified in the table below. The colour only indicates the voltage range; the earth contact position in section 3 must also be read to pin down the correct system. A detailed table explaining each colour is in the article IEC 60309 socket-outlet voltage colour codes.

3. Number of poles and earth contact position by clock hour

The number of poles is given by the number of contacts, including the earth contact E (protective conductor PE): 3 poles is 2P+E (two live poles and earth), 4 poles is 3P+E (three phases, no neutral), 5 poles is 3P+N+E (three phases, neutral N and earth); on site these are often called 3-pin, 4-pin and 5-pin. Phase terminals are marked L1, L2, L3 or 1, 2, 3; the neutral is marked N (Bals catalogue 2016).

The earth contact position is read like a clock face: looking straight at the front of the socket-outlet with the keyway at the bottom, the earth contact-tube lies at one of twelve hour positions. The system voltage is identified by the housing colour together with the hour position of the earth contact (Mennekes catalogue 2016). The notation “6h” means the earth is at the 6 o'clock position. The position diagrams in the standard show the front face of the socket-outlet; plugs and appliance inlets are mirror images (Bals catalogue 2016, according to DIN EN 60309-2).

The table below combines the voltage columns in the Bals product selection table. At the same 230 V, 2P+E is at 6h while 3P+E is at 9h; at 400 V it is the other way round. A plug and a socket-outlet of the same colour and the same number of poles must therefore still match in hour position to mate with each other. For selecting the number of poles and the current for three-phase circuits with neutral, see 3P+N+E industrial socket-outlets: selecting 16, 32, 63, 125 A.

• Voltages up to 50 V: the position of the auxiliary key relative to the major key determines the system, for example 40–50 V, 50 and 60 Hz has the auxiliary key at 12h, white; 20–25 V has no auxiliary key, violet (Bals catalogue 2016).
• In addition to the common positions, the Bals catalogue also lists special types: earth at 1h and 5h for 600–690 V, and 3h for 32 A 4-pole refrigerated container socket-outlets.

4. IP44 and IP67 ratings

The IP code to IEC 60529 consists of two numerals. The first numeral indicates protection against solid objects and access to hazardous parts, ranging from 0 to 6; the second indicates protection against water, ranging from 0 to 8 (IEC 60529, Tables 1 and 2). For industrial plugs and socket-outlets, manufacturers' catalogues divide products into two ratings, IP44 and IP67: Bals states that its plugs and socket-outlets achieve IP44 and IP67, tested to DIN EN 60529, for example at a water depth of 1 m (Bals catalogue 2016); the socket-outlet selection table in the Mennekes Vietnam documentation is also divided into two columns, IP44 and IP67.

Select the IP rating according to the installation environment: workshops with wash-down water, dust, outdoors. For matching each type of workshop to an IP rating, see selecting the IP rating of socket-outlets for damp, dusty workshops.

5. Rated currents 16, 32, 63, 125 A

The Bals catalogue covers four current sizes, 16, 32, 63 and 125 A; the Mennekes Vietnam documentation lists 16, 32 and 63 A sizes. For its four sizes, Bals states full breaking capacity to DIN EN 60309 and permits plugging and unplugging under load up to 690 V a.c. (Bals catalogue 2016, Standards section).

The 63 A and 125 A sizes have an additional pilot contact used for electrical interlocking or monitoring. This contact closes last on insertion and opens first on withdrawal (Bals catalogue 2016). Bals designates part numbers with this contact by the suffix P.

The current size also determines the conductor size that can be connected to the socket-outlet terminals. The rated current of the socket-outlet is the limit of the accessory itself; the supply cable and the protective device of the circuit are still selected by the condition IB ≤ In ≤ Iz, where IB is the design load current, In is the rated current of the protective device and Iz is the current-carrying capacity of the conductor (QCVN 12:2014/BXD, clause 2.6.3.1). See selecting an MCB by load current and coordinating cables and circuit-breakers.

6. Surface-mounted and panel-mounted socket-outlets, plugs and connectors, interlocked socket-outlets

In EN 60309 terminology, a plug-and-socket connection consists of a plug on the end of a flexible cable inserted into a socket-outlet on the supply side; the part fixed to the current-using equipment is called an inlet; a socket on the end of a flexible cable used for extension is called a connector (Bals catalogue 2016, Glossary of terms). The catalogue divides the mounting types as follows.

• Surface mounting socket-outlets: fixed onto the mounting surface, with their own housing; Bals offers IP44 and IP67 versions.
• Panel mounting socket-outlets (flush-mounted): installed on an enclosure panel or housing; available in straight and angled versions, each in IP44 or IP67 (Bals catalogue 2016). For choosing the enclosure that houses the socket-outlets, see switchboards in building projects: board types and how to choose the enclosure.
• Plugs: Bals offers IP44, IP67, angled and padlockable versions. Appliance inlets come in surface-mounted and panel-mounted versions; connectors are used to extend flexible cables.
• Switched and interlocked socket-outlets: IEC 60309-4 applies to products combining, in one enclosure, a socket-outlet to IEC 60309-1 or 60309-2 with a switching device (IEC webstore). With Mennekes interlocked socket-outlets, the switch cannot be turned on until the plug is fully inserted, and the plug cannot be withdrawn until the switch is turned off (Mennekes catalogue 2016). Bals offers surface-mounted switched socket-outlets with double mechanical interlock, lockable in the 0 position.
• Combination socket-outlet units: several CEE 16–63 A socket-outlets, interlocked socket-outlets, with RCDs, fuses and MCBs in one enclosure, available in IP44 and IP67 versions (Mennekes Vietnam documentation, undated). Circuits supplying hand-held equipment must have an RCD with a rated residual operating current not exceeding 30 mA as additional protection (QCVN 12:2014/BXD, clause 2.3.3.4); see how RCCB, RCBO and ELCB differ.

7. Selection steps

Work through the five parameters in this order: number of poles, colour and hour position, current size, IP rating, mounting type. Load, voltage and environment data are taken from the design documents or the machine nameplate.

• Determine the voltage and number of conductors of the load: single-phase, three-phase without neutral or three-phase with neutral. This gives the number of poles: 2P+E, 3P+E or 3P+N+E.
• Look up the colour and hour position in the tables in sections 2 and 3; socket-outlets, plugs and connectors in the same system must match in colour, number of poles, hour position and current size.
• Select a current size of 16, 32, 63 or 125 A not less than the load current, and check the conductor size that can be connected to the socket-outlet; the cable and circuit-breaker of the circuit are selected according to selecting low-voltage cables for building projects.
• Select IP44 or IP67 according to the environment; select the surface-mounted, panel-mounted, plug and connector type, or a switched socket-outlet with interlock where plugging and unplugging under load must be prevented.
• Enter all the parameters above in the bill of materials when requesting a quotation; see preparing a BOQ to receive a quotation quickly.
• Where the board supplying a group of socket-outlets needs current and energy metering: see selecting current transformers by ratio and accuracy class, multifunction meters: reading the specifications and 3-phase meters, direct and via current transformers.