Chapter 2: Installation and configuration
LaserSense 100 Aspirating Smoke Detector Installers Handbook 11
Application
The detector is intended to provide small area incipient fire detection. This means
that it is suitable for the substantial range of applications typified by small
compartmentalised rooms, warehouse racking, or pieces of electronic or
electromechanical equipment where it is desirable to achieve individual incipient
fire reporting. In compartmentalised rooms, each compartment would normally
use an individual aspirating detector.
The detector is not intended to protect large areas, or to sample from areas
where there may be any difference in airflow rates or pressure differentials. If
detection in environments conforming to these descriptions is required, other
type detectors should be used.
System design
Simple designs with short sampling pipes produce the best results. Complex
sampling pipe runs should be avoided with the detector. The use of T-branch
pipes is not recommended. The detector is fitted with two sampling pipe inlets as
standard. It is always preferable to use two shorter pipes as opposed to one
longer pipe. If two sampling pipes are used, care should be taken to keep the
sampling pipe lengths and number of sampling holes on each pipe within 10% of
the other. This can be verified using the PipeCAD system design software.
Unused sampling pipe inlets should be fitted with pipe bungs.
Maximum length of sampling pipe used with the detector is 100 m in still air with
20 sampling holes (or Capillary Remote Sampling Points). This will provide a
transport time from the end of the sampling pipe within 120 seconds. If the
protected area has airflow present, the maximum permitted sampling pipe length
will be reduced. In order for the installation to conform to EN 54-20, pipes must
conform at least to EN 61386-1 Class 1131.
Note: PipeCAD pipe modeling software must be used when designing a pipe
network and verifying its performance.
Always locate the sampling points in positions to which smoke may reasonably
be expected to travel. For example, do not expect ceiling mounted sampling
points to operate satisfactorily if air flow from air-conditioning systems keeps the
cool smoke from an incipient fire from reaching ceiling level. In this instance, it is
usually better to locate the sampling pipe directly in the airflow (for example,
across the return air register of an air conditioning unit).
Note: There is no substitute for carrying out smoke tests prior to installation of
pipework to indicate suitable sampling point location.
No more than two air handling units may be protected with one detector. In this
application, ensure that the sampling pipe is raised clear of high velocity air in the
immediate vicinity of the air intake grill on standoff posts as shown in Figure 5 on
page 12.
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