14.
These are usually installed the ceilings and the top stair wells of
buildings because heat and smoke rise.
In normally closed circuit, the alarm call points are connected series
to normally closed contacts shown Fig.Electrical installations and wiring systems
333
operating even when attacked fire. They should located exit routes and, particular, the
floor landings staircases and exits the street. With monitored system, PVC insulated cables may be
used wire the alarm call points. The alarm call points
of normally open system must also wired FP200 cable, unless
a monitored system used.
Definition
In normally closed circuit, the alarm
call points are connected series to
normally closed contacts shown in
Fig.
FIGURE 14.
Automatic detection fire possible with heat and smoke detectors.4m above the floor easily accessible, well illuminated and
conspicuous positions.48. 14. The sounders
and master control unit must wired FP200 cable, but the call
points may wired PVC insulated cable since this circuit will always
‘fail safe’. breakglass manual call point shown in
Fig.
.48
A simple normally closed fire alarm circuit.
Definition
Manually operated alarm call points
should provided all parts of
a building where people may be
present, and should located that
no one need walk for more than 30m
from any position within the premises
in order give alarm. When the alarm initiated,
or break occurs the wiring, the
alarm activated. They should fixed at
a height 1.
Alarm call points
Manually operated alarm call points should provided all parts a
building where people may present, and should located that no
one need walk for more than 30m from any position within the prem-
ises order give alarm.49. For this reason the master control
and sounders should wired FP200 cable.48. 14. When the alarm initi-
ated, break occurs the wiring, the alarm activated. its simplest form this system requires a
high-value resistor connected across the call-point contacts, which
permits small current circulate and operate indicator, declaring
the circuit healthy.49
Breakglass manual call point. They should able discriminate between fire and the
normal environment which they are installed.
Alarm
sounders
Alarm call points
Master
control
unit
Secure
supply
FIGURE 14. Smoke detectors tend give a
faster response than heat detectors, but whether manual automatic call
points are used, should determined their suitability for the particu-
lar installation
