Detector Installation - Siemens FC2025 Manual

Detector Installation

4.3
Once the detector is selected, the next step is to consider the space that requires protection.
Spot-Type Detectors are usually located on the ceiling or sidewall with the edge of the detector
located no closer than four inches from the wall or ceiling. When Heat Detectors are installed at their
listed spacing, detection times are approximately equivalent to the operating time of standard 165°F
link-and-lever sprinklers. If faster response is desired, reduce detector spacing. Also, where ceiling
heights exceed 16 feet, or where ceiling construction is not smooth, reduce detector spacing
accordingly. Specific information on the treatment of joisted, beamed, and sloped ceilings can be
located in Chapter 5 of NFPA (2002 Edition).
When installing any type of heat detector, consideration should be given to sources of heat within the
protected space that can cause false alarms. For example, locate heat detectors away from unit
heaters and ovens where surges of hot air might be expected.
The installation of Smoke Detectors is more critical than for heat detectors because smoke transport
is strongly influenced by the convective airflow patterns within the protected area. For this reason,
smoke detectors are not assigned a listed spacing by the testing laboratories other than maximum
area coverage of 900 square feet per detector. Although a grid pattern can be used as a starting
point, care must be taken to locate the heating supply registers and return air registers.
Smoke detectors should be located away from turbulence caused by hot air outlets. The location of
the smoke detectors should favor return air because the return air draws smoke toward the detector
and because air velocity at the return tends to be lower.
Smoke stratification also should be considered when smoke detectors are installed. Smoke may
stratify below a ceiling due to temperature gradients or air flow along the ceiling. When stratification is
a possibility, smoke detectors can be installed with alternate detectors at different levels.
Siemens Industry, Inc.
Building Technologies Division
FS20 Marine Fire Detection Control Panel
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