Eclipse Installation, Commissioning & Operating Manual
Approved Document Ref: UI-ECL-01 Issue 8.0
8
DESIGN CONSIDERATIONS
SYSTEM DESIGN & PLANNING - A few handy tips
What is a detection zone?
In order to direct those responding to a fire alarm signal, particularly the fire service, to the area of a fire, all
buildings, other than very small buildings, need to be divided into detection zones. Detection zones need
to be small enough for a fire to be located quickly.
•
If the total floor area of the building is greater than 300m
2
, each zone should be restricted to a single
storey
•
If the total floor area of the building is less than 300m
2
a zone may cover more than a single storey
•
For voids above or below the floor area of a room, these may be included within the same zone of the
room, provided that the void and the room constitute a single fire compartment
•
The floor area of a single zone should not exceed 2000m
2
.
Detectors
•
A person searching a zone for a fire in a non- addressable fire system should not have to travel more
than 60m to identify the source of a fire
•
The sensing element of a smoke detection device should not be less than 25mm and not more than
600mm below ceiling
•
The sensing element of a heat detector should not be less than 25mm and not more than 150mm
below ceiling
•
When mounted on a flat ceiling, smoke detection devices have an individual coverage of 7.5m radius.
However these radii must overlap to ensure there are no ‘blind spots’. Therefore individual coverage
can be represented by a square measuring 10.6m x 10.6m giving an actual coverage of 112m
2
per
device
•
When mounted on a flat ceiling, heat detection devices have an individual coverage of 5.3m radius.
However these radii must overlap to ensure there are no ‘blind spots’. Therefore individual coverage
can be represented by a square measuring 7.5m x 7.5m giving an actual coverage of 56.3m
2
per
device.
Call Points
•
A person should not have to travel more than 45m along an escape route to reach a Manual Call Point
(25m if disabled person to operate, or rapid fire development is likely). Manual Call Points should be
sited at all stair wells and exits from the building.
•
The frangible element of the manual call point should be positioned 1.4m (+/- 200mm) from the floor
level. (Unless a wheelchair user is likely to be the first person to raise the alarm).
Sounders
•
Sounder device cabling should be arranged so that in the event of a fault, at least one sounder will
remain operational during a fire condition.
•
The minimum sound level should be 65dB(A) or 5dB(A) above a background noise which is louder
than 60dB(A) (if lasting more than 30 seconds) and at a frequency of between 500Hz and 1000Hz.
The maximum sound level should not be greater than 120dB(A) at any normally accessible point. This
may be reduced to 60dB(A) in stairways, enclosures up to 60m
2
and specific points of limited extent.
•
For areas where people are sleeping, sounder devices should produce a minimum 75dB(A) at the
bed-head with all doors shut. In buildings providing sleeping accomodation for a significant number
of people, all bedrooms should have both audible and visual alarms.
This guide is intended as an aid
to designers and installers of fire
detection systems. It is NOT to be
used as a substitute to BS5839 which
should be read in full.
