They should fixed at
a height 1. They should located exit routes and, particular, the
floor landings staircases and exits the street.
In normally closed circuit, the alarm call points are connected series
to normally closed contacts shown Fig. 14. When the alarm initi-
ated, break occurs the wiring, the alarm activated. They should able discriminate between fire and the
normal environment which they are installed.48.
Automatic detection fire possible with heat and smoke detectors. 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.
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.49
Breakglass manual call point.
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. 14.Electrical installations and wiring systems
333
operating even when attacked fire.
These are usually installed the ceilings and the top stair wells of
buildings because heat and smoke rise. For this reason the master control
and sounders should wired FP200 cable.48
A simple normally closed fire alarm circuit.
Definition
In normally closed circuit, the alarm
call points are connected series to
normally closed contacts shown in
Fig. The alarm call points
of normally open system must also wired FP200 cable, unless
a monitored system used.48. 14.49. With monitored system, PVC insulated cables may be
used wire the alarm call points. When the alarm initiated,
or break occurs the wiring, the
alarm activated. 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’.
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.
.
FIGURE 14. breakglass manual call point shown in
Fig.4m above the floor easily accessible, well illuminated and
conspicuous positions
