2.2.5 - Supplies for safety services
Safety services
are special installations which come into use in an emergency,
to protect from, or to warn of, danger and to allow people
to escape. Thus, such installations would include fire alarms
and emergency lighting, supplies for sprinkler system pumps,
as well as specially protected circuits to allow lifts to
function in the event of fire.
The special needs
of safety circuits will often be required by authorities
other than the IEE Regulations, especially where people
gather in large numbers. For example, safety circuits in
cinemas are covered by the Cinematograph Regulations 1955,
administered by the Rome Office in England, Wales and Northern
Ireland and in Scotland by the Secretary of State.
Safety circuits
cannot be supplied by the normal installation, because it
may fail in the dangerous circumstances the systems are
there to guard against. The permitted sources of supply
include cells and batteries, standby generators (see
{2.5}) and separate feeders from the mains supply. The
latter must only be used if it is certain that they will
not fail at the same time as the main supply source.
[Chapter 56] contains
six sections and a total of twenty-one Regulations, detailing
the requirements for safety services. In effect, the circuits
concerned must comply with all of the rest of the Regulations,
and with some additional needs.
The safety source
must have adequate duration. This means, for example, that
battery operated emergency lighting must stay on for the
time specified in the applicable British Standard (BS 5266).
Since such installations may be called on to operate during
a fire, they must not be installed so that they pass through
fire risk areas and must have fire protection of adequate
duration.
Safety circuits
must be installed so that they are not affected by faults
in normal systems and overload protection can be omitted
to make the circuits less liable to failure. Safety sources
must be in positions which are only open to skilled or instructed
persons, and switchgear, control gear and alarms must be
suitably labelled to make them clearly identifiable.