6.5.1 - Lighting circuits

Lampholders and ceiling roses must not be used in installations where the supply voltage exceeds 250 V. Where bayonet cap (BC) or edison screw (ES) lampholders are used, the protective device rating is limited to the values shown in {Table 6.3}, unless the lampholders and the associated wiring are enclosed within a fireproof enclosure, such as a luminaire (lighting fitting), or unless they have separate over-current protection in the form of a local fuse or circuit breaker.

Lampholders are often mounted within enclosed spaces such as lighting fittings, where the internal temperature may become very high, particularly where filament lamps are used. Care must be taken to ensure that the lampholders, and their associated wiring, are able to withstand the temperature concerned. Where ES lampholders are connected to a system with the neutral at earth potential (TT or TN systems) care must be taken to ensure that the centre contact is connected to the phase conductor and the outer screw to the neutral to reduce the shock danger in the event of touching the outer screw during lamp changing (see {Fig 6.10}).

Table 6.3 - Overcurrent protection of lampholders
Type of lampholder	-	Maximum rating of protective device (A)
Bayonet cap	SBC	6
	BC	16
Edison screw	SES	6
	ES	16
	GES	16

Fig 6.10 - Correct connection of ES lampholder

Ceiling roses must not have more than one flexible cord connected to them, and, like the flexible cords themselves, must not be subjected to greater suspended weight than their design permits (see {Table 4.2}). Lampholders in bath or shower rooms must be fitted with a protective shield to prevent contact with the cap whilst changing the lamp (see {Fig 6.11}).

In large lighting installations, particularly where fluorescent fittings are involved, consideration should be given to the use of luminaire support couplers (LSCs) or plugs and sockets. Such arrangements facilitate the disconnection of luminaires for electrical maintenance and for cleaning, and may also allow the complete testing of an installation before erection of the luminaires. Many lighting installations are now controlled by sophisticated software (which may switch off the lighting when daylight levels increase or when a room has been unoccupied for a predetermined time). Such devices must be installed to comply with the Regulations.

Fig 6.11 - Protective shield for a BC lampholder