Handbook of Electrical Installation Practice - BeKnowledge

Special Installations or Locations 263
in caravan installations in that due to the modern thin wall caravan construction the
wiring cannot readily meet the installation requirements of Regulation 522-06 of
BS 7671: 2001 without further mechanical protection on the other side of the wall
to the cable route. The industry is currently considering the use of other cable types
with integral earthed metal protection.
Extra low voltage circuit arrangements are required to conform to the BS 7671
requirements for SELV. This places restrictions on the type and nominal voltage of
the ELV source, and the selection and erection of ELV conductors. SELV nominal
voltages are restricted to the preferred values of 12V d.c., 24V d.c. or 48V d.c. with
a dispensation to allow a.c. sources of the same (r.m.s) voltages in ‘exceptional
cases’. In order to secure the satisfactory electrical separation of low voltage and
extra low voltage systems, cables of these two systems should be run physically
segregated. Extra low voltage and low voltage sockets must not be compatible.
Furthermore, extra low voltage sockets are required, as added security, to have
their nominal voltage clearly and indelibly marked.
In respect of some accessories, such as dual voltage luminaires, special requirements
are prescribed in BS 7671 to ensure the separation is maintained. In addition,
specifiers should consider carefully the functional needs of the caravan user
when planning the installation. Many caravan users are practical people who would
encounter little difficulty in altering an existing installation by the addition of nonstandard
luminaires, without realising the potential hazard that may be introduced.
In recognition of the fact that continual movement could damage pendant flexible
cords, BS 7671 actually recommends luminaires to be fixed direct to the body
of the caravan. Where it is necessary to fit pendant luminaires, the practitioner is
required to ensure that the means of suspension of the luminaire is sufficiently
robust for the mass to be supported and to provide adequate anchoring of the
luminaire, to prevent damage while in motion.
As is to be expected, the means of connection of caravans is standardised, and
plugs, sockets and connectors are all to be to BS 4343 standard (now renumbered
as BS EN 60309-2), with the inlet socket not more than 1.8m above ground level
but in a readily accessible position and mounted in an enclosure with a suitable
cover to the outside of the caravan. The flexible cord or cable must not be longer
than 25m and BS 7671 requires it to be in accordance with BS 6007 or BS 6500.
Recent convention has expected a cable rated capacity of 16A; however, modern
caravans and motor caravans are fitted with substantial electrical appliances and in
recognition of this, BS 7671 provides for cables of up to 100A capacity.
Vital to the safety of caravan users is the condition of the electrical installation,
bearing in mind the arduous conditions and the potential for do-it-yourself
additions. BS 7671 recognises this and prescribes a standard format notice to users
advising that the installation should be inspected and tested at least once every
three years.
CARAVAN SITE SUPPLY ARRANGEMENTS
The following notes will apply equally to caravans, motor caravans and tents where
temporary connections are made to moveable leisure accommodation.