6.4.2 - BS 196 socket outlet circuits

BS 196 sockets are two-pin, non-reversible, with a scraping earth connection. The fusing in the plug can apply to either pole, or the plug may be unfused altogether. Interchangeability is prevented by means of a keyway which may have any of eighteen different positions, identified by capital letters of the alphabet (see {Fig 6.7}). They are available with current ratings of 5 A, 15 A or 30 A.

Fig 6.7 Arrangement of socket outlet to BS 196.
Two of the eighteen possible keyway positions are shown

Circuit details for wiring ES 196 outlets can be summarised as:

1. - the maximum protective device rating is 32 A

2. - all spurs must be protected by a fuse or circuit breaker of rating no larger than 16 A - this means that 30 A outlets cannot be fed from spurs

3. - the number of sockets connected to each circuit is unspecified, but proper judgement must be applied to prevent failure of the protective device due to overload

4. - cable rating must be no less than that of the protective device for radial circuits, or two thirds of the protective device rating for a ring circuit

5. - on normal supplies with an earthed neutral, the phase pole must be fused and the keyway must be positioned at point B (see {Fig 6.7})

6. - when the socket is fed at reduced voltage from a transformer with the centre tap on its secondary winding earthed {Fig 6.8}, both poles of the plug must be fused and the keyway must be positioned at P.

Fig 6.8 - Circuit fed from a transformer with a centre-tapped secondary winding