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D296/D297 Series Application Guide 9
If the ceiling beams (joists) exceed 1 ft (.03 m), the spacing between the beams exceeds 8 ft (2.4 m) or the ceiling height exceeds
12 ft, the detectors must be located in every ceiling beam pocket.
Transmitter
Receiver
Ceiling beams (joists)
Transmitter Receiver
Transmitter Receiver
If the fire size is expected to exceed 1-MW (1000 KW), the ceiling height may be up to 28 ft before each beam pocket must be
treated separately. It is recommended that you review
Section B-2 Performance-Based Approach to Designing and Analyzing Fire
Detection Systems
in
NFPA 72
®
, National Fire Alarm Code
®
(2002 Edition)
to determine the potential fire size at the locaton.
6.6.2 Sloped Ceilings
Beamed ceilings with beams running parallel to (up) the slope, the spacing for flat beamed ceilings should be used. The ceiling
height is considered the average height over the slope. For slopes greater than 10 degrees, the detectors located at one-half the
spacing from the low end are not required. Spacing will be measured along a horizontal projection of the ceiling. For beamed
ceilings with the beams running perpendicular to (across) the slope, the spacing for flat beamed ceilings should be used. One set
of beams must be within 3 ft (1 m), measured horizontally, of the high point of the ceiling.
3 ft.
(1 m)
Max.
S
S
½ S
Slope 10° or less
3 ft.
(1 m)
Max.
S
S
Slope greater than 10°
Detector at ½ S not Required