BS 1363

BS 1363 (British Standard) is the more popular of the two standards to which the British electrical plugs and sockets are manufactured.

See also the entry in the mains power plug article on the British three-pin plug.

A BS 1363 plug has two horizontal, rectangular pins for live and neutral, and above these pins, a larger, vertical pin for an earth connection. Unlike many other plugs, the earth pin is mandatory as it is needed to open the shutters. It also polarises the plug. Moulded plugs for unearthed, double-insulated appliances can substitute this contact 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 amperes. The maximum load that can be placed on a socket, including double and triple sockets, is 13 amps. The double sockets are unfused, so it is possible to draw up to 26 amps before hitting the rated current of any overcurrent protection. However when drawing up the standard it was decided to only require double sockets to be able to take 13A total!. Most sockets can stand more than this at least in the short term but continuous running at 26A WILL result in a damaged socket. Surprisingly however this has not posed a problem in practice probably because of the fact that very few domestic appliances draw the full 13A for any significant time. Triple and larger sockets are fitted with a 13 amp fuse of the same type used in the plugs.

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 volts than 230, as the old standard before European harmonisation was 240V +-6%, and most supplies installed to the old standard meet the new standard.

This plug is often referred to as the safest in the world and to many outsiders it often seems excessively safety conscious and somewhat clunky to those not familiar with it. The high extraction force can be inconvenient, particularly to people with weak hands, such as the elderly. To counter this plugs with handles and traps to fit existing plugs and provide a handle have been produced but never really caught on. The large size can make the plugs inconvenient when there are many plugs in a small space, as on extension strips.

Safety measures

Fusing

All plugs with the exception of a few wall warts are fused. This is in addition to fuse boxes or circuit breakers in houses. This is done for two reasons: First, to better protect different types of appliance, and second, to allow high current 32A socket circuits to be used safely. These circuits are usually but not always in the form of ring mains. Fuses for fittings to BS 1363 must conform to BS 1362. This specification describes a sand-filled ceramic bodied fuse, 1" in length and 1/4" in diameter.

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 heavy load (3250 W max.) appliances such as irons, electrical heaters and refrigerators.
Ratings of 1, 2, 7 and 10 amps are available and are all coloured black, but are rare (1A is extremely rare). The fuses are mechanically compatible, but inserting a fuse too weak for the appliance will likely cause the fuse to blow prematurely while using too strong a fuse will degrade safety as the fuse will blow less quickly or not at all in the event of a fault. See Fuse (electrical) for further information.

Shuttering

British power outlets incorporate shutters on the live and neutral contacts to prevent someone from pushing a foreign object into the socket. On most sockets these are opened by the earth pin which is longer than the others and must always be present (though on class 2 equipment it may be plastic).A notable exception to this method of opening shutters are sockets made by MK. These use a proprietary system which seems to depend on the shape of the live and neutral pins and does not depend on the earth pin. Some older sockets simply require equal pressure to be placed upon the live and neutral shutters (towards the outer edges so as to stop insertion of 4mm plugs). On sockets which use the earth pin to open the shutters, said shutters can be opened by inserting an object into the Earth hole (a screwdriver works well for this). Electricians do this frequently to allow them to insert test probes into sockets. 4mm pin European plug types (CEE 7/16, Gost 7396) will fit in after doing this and 4.8mm ones (CEE 7/4, 7/7 or 7/17) will go in if forced, however the lack of earth connection (if the plug has it) and the fact that BS 1363 sockets will often only be protected by a 30A or 32A fuse or breaker (which is much higher than the wiring regs permit for other non industrial socket types) means this is not recommended.

Pin Insulation

The live and neutral pins have insulated bases to prevent finger contact with 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.

others

The plug is polarised, so it should always be clear which lead or prong is live.
Wall sockets usually incorporate switches to turn off the power. The regs require an adjacent switch where this is not incorporated into the socket.
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 tugging on the cable. (This practice — possible with many other plug designs — can be hazardous as it can cause shorts.)
the plug is firmly fitting and therefore difficult to dislodge by accidental knocks or strains on the cord

Euro converter plugs

Some manufacturers/distributers use a special type of plug for conversion of Class 2 appliances from the continent which are fitted with moulded europlugs. Unlike a travel adaptor theese plugs when closed look fairly similar to normal plugs. Inside are two metal clips into which the metal ends of the europlugs pins are clipped. The body of the converter plug is shaped to grip the europlug. The hinged lid is then shut to cover the connections to the europlug and is screwed shut. Theese plugs have a plastic earth pin and a fuse accessible from the outside and in some cases are fitted with screws that are made to be difficult to unscrew.

Socket location

In Britain and Ireland, conventional sockets must not be installed in bath or shower rooms. Light switches cannot be near wet zones in bathrooms, shower rooms or swimming pools and must either be a set distance away, outside the room or fitted on the ceiling and operated by an insulated cord. No such strict rules exist for kitchens or other rooms containing water although the regulations do specify that equipment should be suitable for its environment which would preclude putting normal sockets very close to sinks as they could easily be splashed. Special 'shaver sockets' compliant with BS 4573 are permitted because of their isolated design, and are now common in hotels and modern homes.

Some manufacturers produce sockets which incorporate covers and seals making them suitable for use outdoors or in other wet locations, notwithstanding the above rules. These usually incorporate or are connected through an RCBO to provide additional safety. Some older designs require a specially modified plug to maintain the seal while newer designs can maintain a waterproof seal even when used with a normal plug.

Countries of use

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 and probably other countries where the british have had influence in the past.

The UK, and some of these other countries, also use the older BS 546 round-pin socket standard.