Hochiki FIRElink-400CM - Manual (Page 28)

Page 28 of 58 FIRElink-400 Air Sampling System – Installation Manual
© 2010 Hochiki Europe (UK) Ltd 9-5-0-346/ISS4/OCT10
5 Sampling Pipe Design
Aspirating system design is inherently simple. It is often possible to achieve good system performance
with very simple installations. There are however a few rules which must be adhered to, and these rules
are equally applicable to all aspirating systems which operate on similar principles to FIRElink-400. The
information contained in this Handbook is intended as an overview only. For further information please
see the complete System Design Guide.
 Do not expect one detector to achieve good performance if sampling from areas of different air
pressure (typically: underfloor air plenums and room spaces or different rooms in air-conditioned
areas). This is because the air pressure differences may cause reverse or poor airflow along the
sampling pipes. If it is not possible to locate the detector within the protected area it may be
necessary to lead an exhaust pipe from the detector exhaust port returning air to the protected
area.
 Always locate the sampling points in a position to which smoke may reasonably be expected to
travel. This may sound obvious, but, for example, do not expect ceiling mounted sampling points
to operate satisfactorily if air flow prevents the cool smoke from an incipient fire from reaching
ceiling level. In this instance it is usually better to locate the sampling pipes directly in the airflow
(for example in an air conditioning unit air intake). There is no substitute for carrying out smoke
tests prior to installation of pipes to indicate suitable sampling point location.
 To assist in design and to verify system performance, it is advisable to use the FIRElink PipeCAD®
sampling pipe modelling software.
5.1 Pipework
Sampling pipes should be made from a non-hazardous material and should be clearly identified.
a. The ideal internal diameter of sampling pipes is 22mm. Other sizes will often work but will
provide different response times.
b. Ideally, if the total length of sampling pipe is greater than 50 metres, then multiple pipes should
be used. When using multiple sampling pipes, care should be taken to achieve a reasonable
degree of balance (say within 10% of airflow) to ensure even suction from the pipes.