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BS 1363 British plugs and sockets |
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BS 1363 British plugs and sockets |
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| British standard plugs and sockets according to BS 1363 are introduced in the late 1940s. Used in the UK, Ireland, Cyprus, Malta and several countries in Africa and Asia. |  |
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| 1 | BS 1363 socket. The neutral and live slots are protected by shutters, which are opened by insertion of the longer earth pin. The BS 1363 plug and socket combination is considered a very safe system. Most wall sockets have built-in switches, reducing the need for plug removal when power is not required. The switch is just for convenience, and is not a regulatory requirement. |
| 2 | BS 1363 plug. From 1994 live and neutral pins must have insulting sleeves (black sheathes) to minimize the risk of a shock when pushing the plug in. Insulating sleeves are not allowed for earth pins. These plugs always have a side entry cable, rather than top entry. This feature makes it difficult to unplug it by tugging on the cable, which is an unsafe practice. |
| 3 | Inside view of a
typical BS 1363 plug. Because British circuits (see page on ring circuits)
can deliver more current than many appliance power cords can safely
handle, BS 1363 plugs are required to carry a BS 1362
cartridge fuse. Existing BS 1362 fuse ratings are: 13, 10, 7, 5, 3 or 2
ampere. 13A and 3A fuses are most commonly used (see also comments to
image no.8). Another safety feature is the cord grip that didn't use screws. When wiring the plug, the three internal wires can be cut to the same length because the distance from entry to respectively N, L and E terminal is the same. This makes wiring more easy. |
| 4 | Usually you have to unscrew a BS 1363 plug for replacing the fuse. For moulded plugs and devices that cannot be unscrewed - such as adapter and (some) multi plugs - the fuse is accessible from the outside of the plug. The example shown is a 'shavers only' adapter (see no. 15) |
| 5 | Duplex BS 1363 socket with Residual Current Device (RCD), a safety feature that evaluates the current difference between live and neutral and interrupts the flow of electricity when a sudden difference is measured. The RCD socket complies with BS 7288 (1990). The rated trip current is 30mA; break time is less than 40 msec. Brand name: Smiths (England). |
| 6 | Switched BS 1363 plug. This older example also has an inspection hole in the plug housing, a feature to facilitate verification whether the earth pin is wired, see inset. Modern BS 1363 plugs do not have inspection holes anymore, in contrast to BS 546 plugs. Find more details at the BS 546 page. Note that switched plugs are still available, though most sockets are switched. |
| 7 | Inside
view of a classic, pre-1970s, BS 1363 plug. Wire colours are indicates as
black (Neutral), red (Live) and green (Earth). Early 1970s the colour code for flexible (appliance) cords was changed to: N = blue, L = brown and E = yellow/green (see also N and L pole of plug no. 3). An important reason was avoiding the use of both red and green wires, a serious problem for red-green colourblind people (ca. 6% of men and 0.5% of women). |
| 8 | Late 1950s or early 1960s type of BS 1363 plug equipped with a fuse rating indicator (red arrow). When another type of fuse is installed, the position if the indicator has to be adapted manually. Note the choice between 3A, 7A (!) and 13A plugs. Nowadays 3A and 13A are the preferred BS 1362 fuse ratings. Quite soon after introduction 7A and 10A fuses were deleted from the official list of recommended ratings, but they are still available (as well as 2A and 5A fuses). |
| note | Item nos. 5, 7 and 8 have been donated to the museum; see Acknowledgments. |
| About BS 1363 Starting in the late 1940s, in the UK and Ireland BS 546* round pin plugs and sockets were replaced by BS 1363 devices. This was related to the change of the domestic electrical wiring technique: from radial to ring circuits. Ring wiring necessitated the use fused plugs; see radial and ring circuit page for details. For safety reasons the use of non-fused BS 546 plugs in ring circuits had to be impossible, hence the need to develop a new type of plug. MK Electric and at least two other companies, Wylex and Dorman & Smith, have designed fused plugs. In 1947 the MK type of plug, with rectangular pins, became the new British Standard plug, no. 1363. Wylex and Dorman & Smith plugs and sockets have been used up to the late 1980s. * Note that BS 546 plugs and sockets are occasionally used in the UK for centrally switched lighting circuits, in order to distinguish them from normal power circuits. Some countries of the Commonwealth of Nations still use BS 546, others have adopted BS 1363, and occasionally a mix of "old" and "new" can be found. |
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Non-standard
Besides the standard BS 1363 plugs and sockets, shown on this page, there are
also - both modern and obsolete - variants meant for special purposes. |
Wylex
In the late 1940s, when ring main circuits were introduced several types of plugs were produced as competitors to the BS 1363 standard. |
Dorman & Smith
Another, now obsolete, competitors of the BS 1363 standard, characterized by a combined live pin and fuse. |
| Connectors, multi-plugs and adapters |
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| 9 | Fully approved BS 1363 plug without earth connection. The replacement plastic pin (see arrow; officially known as ISOD = Insulated Shutter Opening Device) is necessary to open the safety shutters of a BS 1363 socket. It also ensures that the plug remains polarized, i.e live and neutral keep their unique positions. The example shows the supply end of a power cord. The other end has a 2-pole C7 type IEC 60320 connector. |
| 10, 11 | 2-pin (neutral and live) and 3-pin (N, L and earth) flex connectors. The male connectors do not have a fuse because extension cables are connected to the main electrical circuit by a fused BS 1363 plug. Both 2 and 3-pin flex connectors are non reversible, because of the ridge and indentation in the housing of respectively the male and female plug (green arrows). Moreover, the pins are positioned off-center in their housing. A 2-pin male plug does not fit in 3-pin female plug, because of a difference in off-center positioning. The 2-pin version (BS 5733) is rated at 10A; the 3-pin version (BS 5733/A) at 5A. |
| 12 | 3-way multi-plug. Also multi plugs are fused to ensure that the maximum load does not exceeds 13A. |
| 13 | Multiway mains plug that allows four appliances to be plugged into one socket outlet. According to the documentation provided: the device is ideal when multiples of electrical appliances are used together without the need to switch them individually on or off. The fused (13A) plug conforms to BS 5733. Brand name: Incept. |
| 14 | Multi-connector, equipped with four mini-plugs (BS 5733). The load of each mini-plug should not exceed 6A. The total load of the multi-connector is restricted to 13A, because of the BS 1363 mains plug. The block includes two mounting holes for wall fitting and is provided with an on/off indicator light. Brand name: Micromark. |
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| 15 | Adapter for shavers,
equipped with a 1A BS 646* fuse. Shavers only adapters can be used
for Europlugs, US 15A flat blade plugs
and British shaver plugs (BS 4573). Note that the adapter plug does not have a transformer (no 120V for US shavers!). * BS 646 fuses are smaller than standard BS 1362 fuses (19.1 mm versus 25.4 mm). |
Remark. Due to EU regulations all manufacturers must ensure that electric shavers are only supplied with a shaver cord which has a 2 pin plug. This is a safety feature. It has been implemented to prevent that shavers are directly plugged into the 240V UK mains socket while shaving, causing possible risk of electrocution when water is involved. Most bathrooms are fitted with a 2 pin shaver socket as this is the only socket which is legally safe in a bathroom. Most hotels in the UK and continental Europe will only have a shaver socket installed in the bathrooms (see item 1 of the museum section on multi-standard sockets). |
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| 16 | Europlug converter, making Europlugs accessible to the UK BS 1363 system. Fully approved by BSI to all relevant standards. |
| 17 | Converter with hinged lid in open position showing the connectors and externally accessible fuse. Since Europlugs are rated for 2.5A a BS 1362 3A fuse has to be fitted. |
| 18 | Converter with Europlug inserted. With closed lid the plug cannot be removed. The lid can be secured with a standard or a tamper resistant screw. Only genuine CEE 7/16 plugs (see Europlug page, image no. 1) fit in this converter |
Note. Also comparable converters exist for NEMA 1-15P flat blade plugs, CEE 7/4 (Schuko) 16A plugs and Italian CEI 23-50, 3-pin 10A plugs. The converter plugs for earthed Schuko and Italian plugs have a fully functional earth pin, rather than a plastic replacement pin (ISOD). |
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| 19 - 21 | Plug key, made in Malaysia. A cheap alternative to the Europlug converter. The large - plastic - earth pin is necessary to clear the access to live and neutral pins. The two smaller pins keeps the key in position. Available in various colours. |
| Serious warning |
The
use of plug keys can be dangerous and is not allowed in the UK. When
used in combination with a plug that has thick round
pins, for example Schuko plugs with 4.8 mm pins, the pins may damage
the contact strips inside the socket. Moreover, British ring circuits
requires the use of fused plugs (see BS 1363 note above). Read more about possible hazards at http://www.fatallyflawed.org.uk/ and the PlugSafe website. |
| 22 | Rubber connector plug for an extension cord (BS 1363/A), made by Dencon Accessories Ltd, UK. See image nos. 23a-d for details about safety features of BS 1363 sockets and connectors. |
| 23a-b | BS
1363 sockets and connectors have to be provided with shutters that
cover at least live and neutral contacts. Shutters prevent the
insertion of any object other than a BS 1363 standard plug. Image no. 23a shows connector no. 22 after removing its housing. The white plastic shutter covers the L and N contacts. The earth pin - on purpose the longest pin of a BS 1363 plug - pushes the shutter aside and the L and N contacts become accessible for the power pins. Image no. 23b illustrates the principle by using a detached earth pin taken from an older BS 1363 plug (pins are secured in modern MK plugs). |
| 23c-d | Image no. 23c shows a BS 1363 plug inserted into connector no. 22. Note the position of the earth slot, about 3 cm (1.2") away from the
edge of the connector housing. This is a relevant detail, because it
prevents insertion of an inverted plug (see the red plug in no. 23d). If it would have been possible to insert an inverted plug, the shutters
are opened and current carrying contacts can the touched by a foreign
object. A potentially dangerous situation. |
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