In a room with a smooth ceiling, detectors should be
spaced between 30 and 60 feet. One-half that spacing be-
tween the beam and the sidewall may be used as a guide.
See Figure 1. The beam detector can be mounted with the
receiver on one wall and the transmitter on the opposite
wall, or both suspended from the ceiling, or any wall/ceil-
ing combination. In the case of the ceiling mount, the dis-
tance from the end walls should not exceed one-quarter of
the selected spacing (7.5 ft. maximum if the spacing is 30
ft.). See Figure 2.
Figure 1. Spacing for smooth ceiling (side view):
1/2 S
S
1 FT.
WALL
A78-2037-00
Figure 2. Spacing for smooth ceiling (top view):
30 FEET MINIMUM
330 FEET MAXIMUM
TX
RX
S
TX
RX
1/2 S MAXIMUM
1/4 S
MAX.
A78-2039-00
In the case of peaked or sloped ceilings, codes may specify
spacing of detectors by using horizontal spacing from the
peak of the roof or ceiling. Figures 3 and 4 show the spac-
ing for both the shed type and peaked type sloped ceilings.
Figure 3. Sloped ceiling (shed type):
S
3 FT. MAX.
S
1/2 S MAX.
Tx
Rx
A78-2036-01
Figure 4. Sloped ceiling (peaked type):
1/2 S
S
S
1/2 S
3 FT.
MAX.
3 FT.
MAX.
MOUNT DETECTOR
ANYWHERE IN THIS AREA
Tx
Rx
A78-2035-01
Mounting Locations
Beam detectors require a stable mounting surface for
proper operation. A surface which moves, shifts, vibrates,
or warps over time will cause false alarm or trouble condi-
tions. Initial selection of a proper mounting surface will
eliminate false alarms and nuisance trouble signals.
Mount the detector on a stable mounting surface, such as
brick, concrete, a sturdy load-bearing wall, support col-
umn, structural beam, or other surface 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 sid-
ing, suspended ceilings, steel web trusses, rafters,
nonstructural beam, joists, or other such surfaces.
D400-18-00
3
I56-494-10R
