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Some fire codes specify spacing on a given center-to-center distance between
detectors under ideal conditions. This spacing is based on rooms with smooth
ceilings and no physical obstructions between the contents being protected
and the detectors. Moreover, they are also based on a maximum ceiling
height, and on the assumption that the value and the combustible nature of
the contents of the room being protected do not warrant greater protection or
closer spacing.
In a room with a smooth ceiling, detectors should be spaced horizontally be-
tween 30 and 60 feet (9.1 to 18.3m). One-half that spacing between the beam
and the sidewall may be used as a guide. See Figure 1. The beam detector
can be mounted with the transmitter/receiver on one wall and the reflector
on the opposite wall, or both suspended from the ceiling, or any wall/ceiling
combination. In the case of the ceiling mount, the distance from the end walls
should not exceed one-quarter of the selected spacing (7.5 ft. [2.3m] maxi-
mum if the spacing is 30 ft. [9.1m]). See Figure 2.
fiGuRE 1. SPAcinG foR SMooTh cEilinG (SiDE viEw):
/
S
1
2
12 IN. MIN.
(0.3M)
30' (9.1M) MAX
TO FIRST
DETECTORS
10' (3.0M)
WALL
MIN.
TYPICAL
fiGuRE 2. SPAcinG foR SMooTh cEilinG (ToP viEw):
Tx/Rx
/
S
1
4
MAX.
Tx/Rx
328 FT. (100M) MAXIMUM
In the case of peaked or sloped ceilings, codes may specify spacing of detec-
tors by using horizontal spacing from the peak of the roof or ceiling. Figures
3 and 4 show the spacing for both the shed type and peaked type sloped
ceilings.
On smooth ceilings, beam smoke detectors should generally be mounted a
minimum of 12 inches (0.3m) from the ceiling or beneath structural obstruc-
tions such as joists, ducts, etc. See Figure 1. In many cases, however, the
location and sensitivity of the detectors shall be the result of an engineering
evaluation that includes the following: ceiling heights above 30 feet (9.1 m) -
refer to the "Single-Ended Reflected Beam Smoke Detector" application guide
A05-0095 for more information regarding the effects of stratification, struc-
tural features, size and shape of the room and bays, occupancy and uses of the
area, ceiling height, ceiling shape, surface and obstructions, ventilation, ambi-
ent environment, burning characteristics of the combustible materials present,
and the configuration of the contents in the area to be protected.
F300-29-00
S
/
S MAXIMUM
1
2
REFLECTOR
S
REFLECTOR
16 FT. (5M) MINIMUM
fiGuRE 3. SloPED cEilinG (ShED TyPE):
3 F T .
( 0 .9 M
) M A X
.
fiGuRE 4. SloPED cEilinG (PEAkED TyPE):
MOUNT SPOT
DETECTOR
ANYWHERE IN
THIS AREA
1
/
S
2
3 F T .
C0254-02
MounTinG locATionS
Beam detectors require a stable mounting surface for proper operation. A sur-
face that moves, shifts, vibrates, or warps over time will cause false alarm or
trouble conditions. Initial selection of a proper mounting surface will elimi-
nate false alarms and nuisance trouble signals.
Mount the detector on a stable mounting surface, such as brick, concrete,
a sturdy load-bearing wall, support column, structural beam, or other sur-
face that is not expected to experience vibration or movement over time. DO
NOT MOUNT the beam detector on corrugated metal walls, sheet metal walls,
external building sheathing, external siding, suspended ceilings, steel web
trusses, rafters, nonstructural beam, joists, or other such surfaces.
In cases where only one stable mounting surface as defined above can be
used, the transmitter/receiver unit should be mounted to the stable surface
and the reflector should be mounted to the less stable surface. The reflec-
tor has a much greater tolerance for the unstable mounting locations defined
above.
MounTinG inSTRucTionS
The transmitter/receiver unit may be mounted over a recessed junction box.
The cavity behind the detector is then used for routing of the wiring from the
junction box to the terminal blocks on the detector. The transmitter/receiver
C0255-00
unit should be mounted to the wall such that unit covers the recessed junc-
tion box in the wall completely. If the junction box is not recessed then you
may use the surface mount kit (BEAMSMK). See the BEAMSMK installation
instructions for surface mounting instructions. The transmitter/receiver unit
can be mounted to the wall using the supplied drilling template (see Appendix
II). The detector base has 4 primary mounting keyholes, one in each corner of
the base. All four hole locations should be used to provide a secure mounting.
The outer housing of the beam detector is held to the base using four screws.
In order to mount the detector you must remove the outer housing first.
The reflector can be mounted to the wall using the supplied drilling template
(see Appendix III). The reflector has 4 mounting holes, one in each corner.
All four hole locations should be used to provide a secure mounting. The
reflector must be mounted such that it is within 10° in both the X and Y
planes of the transmitter/receiver unit. See Figure 5a. The reflector must also
be mounted such that plane of the reflector is perpendicular to the optical
3
S
S
REFLECTOR
Tx/Rx
REFLECTOR
Tx/Rx
S
S
( 0 . 9 M
)
M A X .
1
/
2
3 F T .
( 0 . 9 M
)
M A X .
1
/
S M A X
2
.
C0256-00
S
C0257-02
I56-2425-007R
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