British three-pin .28round.29 plugs and sockets AC power plugs and sockets: British and related types

1 british three-pin (round) plugs , sockets

1.1 bs 546

1.1.1 2 ampere
1.1.2 5 ampere
1.1.3 15 ampere
1.1.4 30 ampere


1.2 characteristics of bs 546 three-pin plugs

british three-pin (round) plugs , sockets

illustration of tripin 3-pin earthed plug dated 1911. note plug has basic characteristics of modern bs 546 plug, 3 round pins, earth pin being longer , thicker other two, , side cable entry.

in 20th century, a. p. lundberg & sons of london manufactured tripin earthed plug available in 2.5 a , 5 a models. tripin described in 1911 book dealing electrical products of a. p. lundberg & sons , pin configuration appears virtually identical modern bs 546 plugs.

the first british standard domestic three-pin plugs bs 317 hand-shield , side entry pattern three-pin wall plugs , sockets (two pin , earth type) published in 1928. superseded in 1930 bs 372 side-entry wall plugs , sockets domestic purposes part ii states there minor alterations bs 317. in 1934, bs 372 part ii in turn superseded first edition of bs 546 two-pole , earthing-pin plugs , socket outlets. bs 546:1934 clause 2 specifies interchangeability bs 372 part ii includes same 4 plug , socket sizes. (bs 372 part standard two-pin non-earthed plugs never included in bs 546 , incompatible due different pin spacings.)

also in 1934 10th edition of iee’s “regulations electrical equipment of buildings” introduced requirement sockets have earth contact.

prior bs 546, british standards domestic plugs , sockets included dimensional specifications socket contact tubes. in bs 546 there no dimensions socket contacts, instead required make contact specified plug pins.

before introduction of bs 317, gh scholes ltd (wylex) introduced (in 1926) alternative three-pin plug. in 3 sizes, 5 a, 10 a , 15 a round earth pin , rectangular live pins, fused 13 a version of continued available after introduction of bs 1363, illustrating bs 546 not used exclusively @ time.

although still permitted uk wiring regulations, bs 546 sockets no longer used general purposes. of varieties remain in use in other countries , in specialist applications such stage lighting.

when bs 546 in common use domestically in uk standard did not require sockets shuttered, although many were. current revision of standard allows optional shutters similar of bs 1363. current uk wiring regulations require socket outlets installed in homes shuttered.

bs 546

bs 546 3-pin plugs. left right: 15 a, 5 a , 2 a.

there 4 ratings of plug , socket in bs 546, (2 a, 5 a, 15 a , 30 a). each has same general appearance different physical sizes prevent interchangeability, use pin spacing different 2 pin plugs specified in bs 372, earthed plugs not fit unearthed sockets, , vice versa. plugs fitted bs 646 fuses have been optional since original bs 546:1934 maximum fuse ratings of 2 a in 2 a plug, , 5 a in 5 a, 15 a , 30 a plugs. in practice bs 546 plugs unfused fused versions being unusual , expensive.

the 15 ampere (a) sockets given dedicated 15 a circuit. multiple 5 a sockets might on 15 a circuit, or each on dedicated 5 a circuit. lighting circuits fused @ 5 a used feed 2 a sockets. adaptors available 15 a down 5 a , 5 a down 2 a in practice possible appliance smallest size of flex protected 15 a fuse. similar level of protection seen portable appliances in other countries, less protection offered bs 1363 fused plug.

the larger top pin earth connection, left hand pin neutral , right hand pin line when looking @ socket or @ rear of plug.

2 ampere

this plug used connect low power appliances (and adaptors larger socket types). still used connect lamps lighting circuit.

5 ampere

5 a switched socket-outlet bs 546

this plug corresponds type d in iec table. in uk used moderate sized appliances, either on own 5 a circuit or on multi socket 15 a circuit, , on many adaptors (both multi socket 5 a adaptors , adaptors had 15 a pins). 5 a plug, along 2 a cousin, used in uk centrally switched domestic lighting circuits, in order distinguish them normal power circuits, quite common in hotel rooms. plug once used in theatrical installations same reasons 15 a model below.

15 ampere

15 a switched socket-outlet bs 546

this plug corresponds type m in iec table. largest in domestic use , commonly used in uk indoor dimmable theatre , architectural lighting installations.

30 ampere

the 30 a plug largest of family. used high power industrial equipment 7.2 kw, such industrial kitchen appliances, or dimmer racks stage lighting. plugs , sockets of industrial waterproof design screw locking ring on plug hold in socket against waterproof seals, , sockets had screw cap chained them used when no plug inserted keep them waterproof. use of bs 546 30 a plugs , sockets diminished through 1970s replaced bs 4343 (which later became iec 60309) industrial combo plugs , sockets.

characteristics of bs 546 three-pin plugs

bs 546:1950 (current version confirmed october 2012) specifies pin dimensions in decimal fractions of inch, shown below. metric values conversions provided here convenience. note, original lengths of line , neutral pins on 15 , 5 amp versions longer @ 0.812 inches (20.6 mm) , 0.625 inches (15.9 mm) respectively.