Bosch DS241 - Manual

Installation Instructions

DS240 and DS241

Long Range Beam Smoke Detectors

1.0

Description

The DS240 and DS241 are long range projected beam type smoke
detectors which consist of a separate transmitter and receiver. Internal
pointability provides coverage flexibility without the need for brackets.
Automatic Signal Synchronization and Range Adjustment reduce
installation costs. Selectable sensitivity and alarm response time
provide installation flexibility.

2.0

Specifications

• Operating Voltage: DS240: 18.0 VDC to 32.0 VDC

DS241: 10.2 VDC to 15.0 VDC

• Standby Current:

DS240: Receiver: 45 mA @ 24.0 VDC

Transmitter: 20 mA @ 24.0 VDC

DS241: Receiver: 50 mA @ 12.0 VDC

Transmitter: 20 mA @ 12.0 VDC

• Receiver Alarm

Current:

DS240: 60 mA @ 24.0 VDC
DS241: 75 mA @ 12.0 VDC

• Range (distance

between transmitter
and receiver):

30 ft to 350 ft (9 m to 107 m)

• Spacing (distance

between systems): Allow no more than 60 ft (18 m) between

systems. Sixty foot spacing is confirmed
by Underwriters Laboratories, Inc. testing.

• Pointability:

Internally pointable optics for ±90°
horizontal, and ±10° vertical adjustment.

• Sensitivity:

Field selectable for 20, 30, 40, 50, 60, or
70 percent beam obscuration.

• Alarm Contacts:

Normally Open contacts rated 1 A,
60 VDC maximum for DC resistive loads.
Do not use with capacitive or inductive
loads.

• Trouble Contacts:

Normally Closed contacts rated 1 A, 60 VDC
maximum for DC resistive loads. Do not
use with capacitive or inductive loads.

• Aux. Alarm

Contacts:

Form "C" (NO, C, NC) contacts rated 1 A,
60 VDC maximum for DC resistive loads.
Do not use with capacitive or inductive
loads.

• Tamper:

Receiver:

Access door tamper switch in
series with trouble contacts.

Transmitter: Upon cover’s removal, cover

tamper switch interrupts
transmission.

• System Signaling:

Conventional 4-wire system. Not for use
with systems that incorporate an alarm
verification feature.

• Signal Delay:

Fire:

Selectable 30 sec or 5 sec

Trouble:

20 ± 2 sec

• Temperature:

The storage and operating temperature
range is -22°F to +130°F (-30°C to +54°C).
For UL Listed installations, the range is
+32°F to +130°F (0°C to +54°C).

• Mounting:

The units are designed to be mounted to
4 in. (10 cm) square or octagonal
electrical boxes (not supplied).

• Listings and

Approvals:

U L

S3019

ULC

CS692

MSFM

Permit #1943

NY City MEA

Acceptance #MEA274-93-E

CSFM

#7260-1062:106

FM

Job #OX2A9.AY

• Standard

Accessories:

DIS2000 Remote Test/Indicator Plate and
Test Cable

• Options:

DIS240 Remote Indicator Plate, TK240
Field Test Kit, AL240 Alignment Light, and
TC2000 Test Cord.

3.0

Principle of Operation

Each DS240 or DS241 beam smoke detector has a separate
transmitter and receiver. The transmitter transmits an invisible infrared
beam of a specific frequency and intensity. The receiver detects, then
measures the beam’s intensity (see

Figure 1).

Figure 1 - Infrared Transmission

As the beam is obscured by smoke, the receiver senses a decrease
in the signal strength and measures that decrease. The receiver
compares the signal level with two preset thresholds: an alarm
threshold which is set using the sensitivity switch and a trouble
threshold which is preset at approximately 10%. If the signal falls
below the alarm threshold for the programmed alarm period, the
receiver signals an alarm (see

Figure 2).

Figure 2 - Beam Obscuration

If the signal falls below the trouble threshold for more than 20 sec,
such as might happen if the beam is blocked by a foreign object, the
receiver signals a trouble condition (see

Figure 3).

Figure 3 - Beam Blockage

The receiver automatically compensates for the gradual loss of signal
due to dust/dirt build-up on the cover. After 50 percent of the signal is
lost, the receiver will indicate a trouble. When the dust/dirt build-up is
cleaned or the blockage is removed, the detector automatically goes
back to its normal operation level.

A trouble will be indicated at the receiver if the beam strength is
increased by more than 20% for greater than 20 sec. Causes include
improper initial alignment or the removal of a partial beam blockage
at the time of alignment. Preform a fine-tune alignment (see

Section

7.3 Fine Tune Alignment on page 6).

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