5
Spacing
The maximum spacing between the axes of ad-
jacent beam detectors is typically 15m for satis-
factory detection under fl at ceilings, providing
a maximum total area coverage of 1500 square
metres (15m x 100m).
The minimum spacing between the axes of ad-
jacent detectors is expressed by the following
equation:
S
≥
L x 0.0875
where S is the spacing and L is the distance
between the detector and the refl ector.
The following table is based on this equation.
SYSTEM DESIGN
Positioning refl ective beam detectors
The intelligent refl ective beam detector must be
positioned correctly to minimise the detection
time. The detection time depends on
—the location of the beam detector within the
protected area
—the volume of smoke produced
—the con struc tion of the roof
—the ventilation arrangements
When deciding where to install the beam detec-
tor and the refl ector, you need to think of the
construction of the surface you are fi tting it to and
to possible changes as a result, for example, of
changing seasons. These surfaces must be solid
and should not be subject to movement.
Particular areas where beam detectors should
not be fi tted include:
• spaces where the detector is subject to
very high levels of ambient light in normal
conditions
• areas where excessive amounts of dust,
smoke or water vapour are present as part
of the normal environment
• areas where temperature changes rap-
idly
• surfaces subject to vibration or movement,
such as cladding or purlins
• buildings in which it is not possible to mount
the beam detector rigidly or align it cor-
rectly
Ensure that spacing complies with the locally
applicable code or standard.
Distance (m)
Minimum spacing
between devices (m)
5
0.44
10
0.87
15
1.31
20
1.75
25
2.19
30
2.62
35
3.06
40
3.50
45
3.94
50
4.37
55
4.81
60
5.25
65
5.69
70
6.12
75
6.56
80
7.00
85
7.44
90
7.87
95
8.31
100
8.75
Table 1 Minimum spacing between detectors
