Bosch D296 - Use correct wire gauge and length; Provide a stable mounting surface

Long-range beam smoke detectors Installation considerations | en 9
Bosch Security Systems, Inc. Installation manual 2017.03 | 7.0 | F.01U.068.899
Bare fluorescent lights can also create a problem, especially in long hallways where a series of
lights are perpendicular to the beam. Incandescent lights are not a problem as long as they
are not directly in the beam path.
3.3 Use correct wire gauge and length
Beam smoke detectors are often used to protect large areas, requiring long wire runs to
power the detectors and signal alarm conditions. The voltage available at the end of long wire
runs might not be sufficient to power the detector, especially when the system is running on
backup battery power. Use the correct wire gauge when installing detectors.
D296 Smoke detector, long-range beam 24V
For the proper number of D296 transmitter and receiver pairs depending on wire size and
length, see the following table.
Wire Length Wire Size
14AWG
(ISO2.5mm
2
)
16AWG
(ISO1.5mm
2
)
18AWG
(ISO0.75mm
2
)
500ft. (152m) 8 pairs 5 pairs 3 pairs
1000ft. (304m) 4 pairs 2 pairs 1 pair
1500ft. (457m) 2 pairs 1 pair 1 pair
2000ft. (609m) 2 pairs 1 pair 0
2500ft. (762m) 1 pair 1 pair 0
Tab.3.1: Wire Gauge and Length
D297 Smoke detector, long-range beam 12V
For the proper number of D297 transmitter and receiver pairs depending on wire size and
length, see the following table.
Wire Length Wire Size
14AWG
(ISO2.5mm
2
)
16AWG
(ISO1.5mm
2
)
18AWG
(ISO0.75mm
2
)
100ft. (30m) 7 pairs 4 pairs 2 pairs
250ft. (76m) 2 pairs 1 pair 1 pair
400ft. (122m) 1 pair 1 pair 0
550ft. (168m) 1 pair 0 0
700 ft. (213m) 1 pair 0 0
Tab.3.2: Wire Gauge and Length
3.4 Provide a stable mounting surface
Beam smoke detectors depend on the projected beam measurement to sense smoke. Trouble
or alarm conditions can be caused by shifts in beam alignment when the transmitter or
receiver moves.
Never mount a detector to pipe or length of wood that is supported at only one end. This type
of suspended support can create a pendulum effect. The pendulum effect greatly multiplies
even very small movements at one end of the support. Support mounting surfaces at opposite
corners to reduce the pendulum effect.