Planning
Installation surface
4
45
Building Technologies
007016_i_en_--
Fire Safety 2012-09-07
4.9 Installation surface
The detector must be installed on a stable and vibration-free surface. Remember
that large fluctuations in temperature (e.g. between day and night) can cause slight
deformations to iron girders etc. If the detector is installed on an unstable surface,
the infrared ray may not reach the reflector and therefore causes an alarm or fault.
The following are examples of unstable installation locations:
Walls of non-insulated rooms with steel constructions. These move due to the
lengthwise expansion of steel.
Bricked walls, on which a steel roof construction is placed.
In such cases, the detector must be installed on a stable surface, while the reflector
can be installed on the unstable wall.
Example
The example below illustrates how the infrared ray is deflected by the influence of
heat on a hall roof's steel construction.
DLR FDL
l
β
Δl
h
c
Incorrect installation: The infrared ray no longer reaches the reflector as a result of
deflection.
c Deflection of the infrared ray Δl Lengthwise expansion
l Length of the roof h Room height
Wanted: Deflection of the infrared ray c
Known:
l Length of the roof 80 m
α Expansion coefficient of steel 12 x 10
-6
K
-1
ΔT Difference in temperature 40 K
h Room height 4 m
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