Product guide

page
22
APPROVALS
Discovery detectors comply with EN54-5:2000 and
EN54-7:2000. Detectors also comply with EMC
Directive 89/336/EEC and are CE marked.
Discovery detectors have been approved by several
approval and regulatory bodies woldwide, including
LPCB in the UK, VdS in Germany, DBI in Denmark
and SSL in Australia.
PATENTS HELD
Protocol interrupt system
Addressable isolators
Addressable XPERT card
It follows, then, that
Discovery detectors set to
mode 1 will be most
suitable for environments in
which sources of unwanted
alarms are rare. Such
environments include
cleanrooms and computer
suites. At the other extreme,
response mode 5 will be
suited to more dusty or
smoky environments such
as loading areas where
diesel forklift trucks are
operating. Response mode
3 is a general-purpose
setting for which the
response is similar to that of
the corresponding XP95
detector.
It will be seen, then, that it is
often more useful to think of
particular response modes
being suited to different
environments rather than
simply having different
sensitivity to fire. Table 7
shows response modes for
Discovery detectors that are
considered suitable for
different environment types.
Any of those identified as
suitable should give
acceptable performance.
The recommended
detector/mode combinations
will give the best available
performance from
Discovery.
Time-related systems
Discovery detectors are
particularly useful for
installations in which it is
desirable to set different
detector response
characteristics at different
times of the day because of
changes in the environment.
For example, if an industrial
process generates smoke or
fumes during working hours
and the area is clean at
other times the optimum
response mode will be
different at different times of
the day. Outside working
hours the sensitivity can be
switched to a higher level to
conditions by selecting the
correct mode (see Table 7).
The relative performance of
the four detector types for
different fire types is given in
Table 6.
Choice of Response Mode
A major objective in
designing a detection system
is to achieve the best
detection performance while
keeping the number of
unwanted alarms at a low
level. Unwanted alarms are
normally caused by
environmental influences.
For any given environment,
unwanted alarms will, as a
rule, be more frequent for
detectors of higher
sensitivity.
It has already been pointed
out that the response modes
for Discovery detectors
correspond to different
sensitivity to fire, with
response mode 1 being
more sensitive than mode 5.
maintain maximum
protection.
The Discovery multisensor
is especially suitable for
time-related systems.
Because its response can be
switched from a pure heat
response to a sensitive
multisensor smoke
response, it can be
optimised for very clean or
dirty (smoky) environments.
However, if mode switching
between heat and smoke (or
multisensor) modes is used,
it is important to remember
that the area coverage in the
heat-only mode is half that
of the smoke or multisensor
modes.
The detector spacing must
therefore be based on the
heat detector spacing of the
relevant standard.