BS 1363
BS 1363 (British Standard) is the more popular of the two standards to which the British electrical plugs and sockets are manufactured.
Main article: Mains_power_plug#Type_G_.28British_3-pin.29.
A BS 1363 plug consists of two horizontal, rectangular pins, polarised as Live and Neutral, and above these pins, a larger, vertical pin for an Earth connection.
Unlike many sockets, the Earth pin is mandatory, although moulded plugs for unearthed, double-insulated appliances can substitute this connector with a plastic pin.
These plugs are required to carry a cartridge fuse manufactured to BS 1362, which can be rated at 3, 5, 10 or 13 amps. The maximum load that can be placed on a socket is 13 amps, including double and triple sockets. The double sockets are unfused, so it is theoretically possible to draw up to 26 amps, although this would not be safe. Triple and larger sockets are fitted with a 13 amp BS 1362 fuse.
The plugs and sockets are designed to carry up to 250 volts AC, 50 hertz. The UK power system is officially 230V +10% -6%. However in reality voltages are generally closer to 240 than 230 as the old standard before Harmonisation was 240V +-6% and most supplies installed to the old standard come within the bounds of the new standard.
Safety measures:
- The plug is polarised, so it should always be clear which lead/prong is live.
- All plugs are earthed and fused. This is in addition to fuseboxes/circuit-breakers in houses. This is done for two reasons firstly to better protect different types of appliance and secondly to allow high current 32A socket circuits to be used safely these circuits are usually but not always in the form of ring mains.
- 3 amp fuses (colour-coded red) are intended mainly for small load (750 W max.) appliances such as radios and desk lamps.
- 5 amp fuses (black but so are other less common ratings) are for medium load (1250 W max.) appliances such as desktop computers and TV sets.
- 13 amp fuses (colour-coded brown) are for big load (3250 W max.) appliances such as irons, electrical heaters and refrigerators.
- other ratings are available and are all coloured black but are fairly rare. The fuses are mechanically compatible, however inserting a fuse too weak for the appliance will likely cause the fuse to blow prematurely while using a too strong fuse will degrade security as the fuse will blow less quickly. See Fuse (electrical) for further information.
- British power outlets incorporate shutters on live and neutral contacts to prevent someone from pushing a foreign object into the socket. The longer earth pin opens these shutters on plug insertion (as it goes in first). This also prevents European plugs from being inserted (which would have no earth connection). However, this safety feature can (dangerously) be foiled by jamming a long object into the earth hole to open the shutters, and then inserting a 4 mm CEE 7/16 plug; even 4.8 mm plugs such as CEE 7/4, 7/7 or 7/17 can be forced in, at risk of damaging the socket.
- The live and neutral pins have insulated bases to prevent clumsy fingers touching the pins and also to stop metal sheets (e.g. fallen blind slats) from becoming live if lodged between the wall and a partly pulled out plug. (A downside to this prong insulation is that it may contribute to damaged sockets not making good contact with the prongs, which may even melt the latter. No such problems exist with healthy sockets.)
- The cable always leads off to the side of the plug, thus making it difficult for people to unplug the (quite firmly fitting) plug by yanking the cable. (This practice — possible with many other plug designs — can be hazardous as it might cause shorts.)
- Wall sockets usually incorporate switches to turn off the power.
- Most extension strips have small lights to indicate when they are live.
- By law in Britain and Ireland, conventional sockets must not be installed near wet zones (basins, baths, showers). Even light switches cannot be near wet zones and must either be outside the room or on an insulated cord that pulls a ceiling switch. Special 'shaver sockets' compliant with BS 4573 are permitted because of their isolated design, and are now common in hotels and modern homes.
The earth pin (the longer one) is slightly longer than the current-carrying pins to ensure that it makes contact with the socket first. Note the insulation around the top of the live and neutral pins. It's there to stop people from touching the pin should the plug only be partially inserted in the socket.
This is probably the safest plug and socket system in the world, although it often seems excessively safety conscious and somewhat clunky to those not familiar with it. It is almost impossible to dislodge by accident partly because the cord enters the plug at right angles to the pins, so force on the cord is not in the direction of extraction. The large size also permits a high extraction force. Electrical cords often come under some tension e.g. when a mobile appliance such as a vacuum cleaner is being used, or when a cable is kicked under a desk. Conversely, people familiar with this plug and not others are often surprised at ease with which other plugs become dislodged or disconnected by accident.
The high extraction force can be inconvenient, particularly to people with weak hands such as the elderly. The large size can make them inconvenient when there are many plugs in a small space, such as on extension strips.
This design is in use not only in the United Kingdom, but also in Ireland, Cyprus, Botswana, Ghana, Malta, Hong Kong, Malaysia, Oman, Singapore, Kenya, Iraq and Qatar to name a few countries.
The UK, and some of these other countries, also use the BS 546 socket standard.
