Environmental Considerations - Bosch D296 Application Manual

D296/D297 | Application Guide | 2.0
2.3

Environmental Considerations

2.3.1 Outdoor
Do not use the D296/D297 Series for outdoor
applications. Environmental conditions such as
temperature extremes, bright sunlight, rain, freezing
rain, snow, sleet, fog and dew can interfere with the
proper operation of the detector. Outdoor conditions
also make smoke behavior impossible to predict.
2.3.2 Indoor
Avoid sources of heat and air movement.
•
Do not mount the D296/D297 Series
where hot or cold air can blow directly
into the beam path.
•
Heating, ventilating, and air conditioning
(HVAC) systems and ceiling fans can
cause smoke to blow away from the
projected beam. Smoke must
accumulate in the projected beam to be
detected.
•
Heaters mounted close to the projected
beam path can cause the beam to be
distorted.
Avoid sources of bright light.
•
Sunlight: Avoid pointing the receiver
directly at the rising or setting sun. If you
are installing the unit where sunlight
cannot be avoided, mount the receiver
slightly higher than the transmitter and
aim it down towards the transmitter. This
reduces the problem by causing the
receiver to look below the horizon.
•
Bright lights: Generally, bright lights are
not a problem. Do not place exposed
bulbs of high-pressure sodium, mercury
vapor, and metal halide close to the
receiver. Bare fluorescent lights might
pose a problem in long hallways where a
series of lights run perpendicular to the
beam.
2.3.3 Mounting
Section 5.7.3.4.8 of NFPA 72, National Fire Alarm
Code (2002 Edition) states: "The light path of
projected beam-type detectors shall be kept clear of
opaque obstacles at all times."
Section A.5.7.3.4.8 of NFPA 72, National Fire Alarm
Code (2002 Edition) states: "Where the light path of
a projected beam-type detector is abruptly
interrupted or obscured, the unit should not initiate
an alarm. It should give a trouble signal after
verification of blockage."
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Applications
Because the D296/D297 Series is a line-of-sight
device that goes into trouble on a sudden and total
loss of signal, ensure all obstacles are clear of the
beam path at all times.
This requirement might cause the detectors to be
impractical in factory applications where overhead
cranes and hoists are present and in warehouses
where high forklifts might block the beam. Also,
consider this factor in occupied areas where there
are normal ceiling heights.
The D296/D297 Series depends on the
measurement of the projected beam to sense smoke.
Shifts in the beam alignment from transmitter or
receiver movement can cause trouble or alarm
conditions. Refer to Figure 3.
Figure 3:
1 - Multiple level mounting locations
Bosch Security Systems, Inc. | 01/07 | F01U500951-01
Multiple Level Mounting
•
Always select a stable mounting
surface. The walls and attached
girders of steel-sided buildings
(especially walls facing the sun) might
be very unstable throughout the day. In
this circumstance, a roof support
girder might provide better support.
•
Never mount the units on a suspended
support such as a pipe or length of
wood supported at only one end.
•
Never use mirrors to extend the beam
around corners.
•
Never mount the units behind clear
glass or plastic covers other than
those supplied by Bosch Security
Systems, Inc. with the detectors.
•
When mounting in high ceiling areas
such as atriums, consider several
mounting levels to account for
stratification due to ceiling height or
low energy fires.
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