Bosch DS240 User Manual download pdf (Page 2)

4.0 Installation Considerations

The proper location and spacing of detectors is critical in a properly

installed and operating fire alarm system. For best results, it is

recommended that the detectors be located and spaced in

accordance with the National Fire Protection Association (NFPA)

Standard 72 "The National Fire Code.” This standard is available at a

nominal cost from The National Fire Protection Association,

Batterymarch Park, Quincy, MA, 02269.

In all installations, good engineering judgement should prevail. The

following are some general considerations:

• Do not use mirrors. The detectors should be installed with a

clear line-of-sight between the transmitter and receiver.

• The beam path should be clear of moving objects.

• Set the sensitivity based on the distance between the transmitter

and receiver. See

Section 7.2 Sensitivity Adjustment

on page 5.

• The detectors may be mounted directly to the ceiling or to side

walls. Do not mount the units where the beam path may run

parallel within 4 in. (10.2 cm) of a corner.

• For a sloped or peaked ceiling, the beam path should be located

within 3 ft (1 m) of the ceiling’s peak.

• Stratification of air may hinder smoke from reaching detectors

mounted close to the ceiling. Stratification occurs when smoke,

rising because it is warmer than the surrounding air, reaches a

level where it is the same temperature as the surrounding air

and will not rise to the ceiling. If stratification is considered a

possibility, extra beams should be installed where stratification

is expected.

• Avoid areas subject to normal smoke concentrations such as

kitchens and garages.

• Do not install units where normal ambient temperatures are

below -22°F (-30°C) or above +130°F (+54°C).

The following are some specific installation considerations:

4.1 Avoid Sources of Heat and Air Movement

The detectors should be located where the beam path will not pass

near heating and cooling outlets.

• Don’t mount where hot or cold air can blow directly into the beam

path.

• Heating, ventilating, and air conditioning systems can cause

smoke to be blown away from the beam path.

- Smoke must accumulate in the beam path to be detected.

• Heaters mounted close to the beam path can cause the beam to

become distorted.

You can test for beam distortion by monitoring the signal voltage.

After setup, the signal voltage of the detector should read 4 VDC.

Monitor the voltage and turn on all heating and cooling devices in the

area. The signal voltage should not fluctuate more than 0.20 VDC. If

it does, the detector should be moved to avoid these disturbances.

4.2 Avoid sources of bright light

Sunlight and light from extremely bright sources such as the exposed

bulbs of high pressure sodium, mercury vapor, and metal halide

lights can cause stray signals. The receiver should not be pointed

toward any of these sources.

Sunlight: Avoid pointing the receiver directly at the rising or setting

sun. If you are installing the unit where sunlight can’t be avoided,

mount the receiver slightly higher than the transmitter and aimed

down toward the transmitter. This should reduce this problem by

causing the receiver to look below the horizon.

Bright Lights: Don’t mount the receiver where it is looking at exposed

bulbs of high pressure sodium, mercury vapor, and metal halide

lights. The illustration below shows where these exposed lights

should be avoided.

225 ft. (68.6 m)

350 ft. (106.8 m)

4.5 ft. (1.4 m)

Keep bright lights out of this area

14.5 ft.

(4.4 m)

Receiver

Bare fluorescent lights may also pose a problem especially in long

hallways where a series of lights run perpendicular to the beam.

Incandescent lights are not a problem as long as they are not directly

in the beam path.

4.3 Use the correct wire gauge and length

Beam smoke detectors are often used to protect very large areas.

This means that the wire runs used to power the detectors and signal

alarm conditions can be very long. The voltage available at the end of

very long wire runs may not be sufficient to power the detector,

especially when the system is running on battery backup. It is very

important that the correct wire gauge is used for these installations.

Use the following chart to determine the proper wire size, wire length

and the number of transmitter and receiver pairs that can be used.

eriW

htgneL

eziSeriW

GWA41

)mm8.1(

GWA61

)mm5.1(

GWA81

)mm2.1(

)m251(tf005

)m403(tf0001

)m267(tf0052

)m4251(tf0005

sriap02

sriap01

sriap4

sriap2

sriap31

sriap6

sriap3

riap1

sriap8

sriap4

sriap2

riap1

1 2 3 4 5 6 7 ... 11 12

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Bosch DS240 User Manual Page 2

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