Bosch D341P Specsheet

Fire Alarm Systems | D285DH Photoelectric Duct Smoke Detector Head (12 VDC or 24 VDC)

D285DH Photoelectric Duct Smoke
Detector Head (12 VDC or 24 VDC)

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u Commercial or residential applications

u Two-wire or four-wire application, depending on

base

The D285DH duct detector head detects the large
smoke particles which typically result from wood,
paper, and fabric combustion.
The detector is part of a two component system: the
duct detector housing and the duct detector head. The
housing is permanently attached on the duct. The
interchangeable duct detector head quickly detaches
for replacement and cleaning without affecting circuit
wiring. The duct detector head attaches to the
following duct detector housings:

• D340 Two-wire Duct Detector Housing (12 VDC or 24
VDC)

• D341 Four-wire Duct Detector Housing (24 VDC or
120 VAC)

• D342 Four-wire Duct Detector Housing (24 VDC or
220/240 VAC)

Functions

Detection chamber operation

The duct detector uses an infrared (IR) LED light
source and a silicon photodiode to measure light in a
chamber. In normal conditions the light is absorbed in
the chamber. The presence of a significant number of
particulates allows the light to reflect to the
photodiode. After three consecutive measurements
exceeding the basic level, the unit signals an alarm

u Chamber Check rapid-flash LED Automatic Trouble

Indication reports contaminated chamber

u Flashing LED power indicator

u Steady-On LED alarm indicator

condition. The detector can be reset from the panel,
after an alarm condition is cleared, by interrupting
power.
The detection chamber, designed for reliable smoke
entry characteristics, is protected by a micro-fine
insect screen to reduce dust accumulation and insect
penetration and minimize nuisance alarms.

Chamber Check Feature

To further reduce nuisance alarms, the detector head
checks its calibration. This Chamber Check feature is
automatic. If the head is out of calibration for a period
exceeding 24 hours, the Trouble-Alarm LED flashes
once per second, three times the normal rate.

Testing

Internal diagnostic test
This head has a moisture-proof reed switch that reacts
to an external magnet for testing. The magnet test
simulates a 4% to 6% smoke obscuration, which
places the detector in an alarm condition. This test
results in specific LED and alarm circuit responses
indicating the:

• Detector is within calibration standards

• Detector settings are outside sensitivity standards

• Detector is not operational

2 | D285DH Photoelectric Duct Smoke Detector Head (12 VDC or 24 VDC)

This test is especially useful in environmentally
unstable or unclean areas.
Sensitivity voltage test
This detector head has a socket that accepts the
D1005 Test Cable. The D1005 connects to the
detector head and allows a voltmeter to read the
sensitivity of the device.

LEDs

The detector has a built-in LED that flashes to indicate
the device is powered. The LED latches on steady in
an alarm condition.

Certifications and approvals

Region Certification

USA UL UROX: Smoke - Automatic Fire Detectors

(UL268 and A)

CSFM see our website

MSFM permit #2186

Hong Kong HKFSD J-005/C/019

Installation/configuration notes

Installation

The duct detector head is part of a compound device.
The duct detector housing installs on the duct and
contains all the wiring. The duct detector head
attaches to the base by aligning the head with the
base and turning it clockwise. No tools are required
for installation other than a screwdriver to tighten the
optional tamper screw.

Wiring

The terminal block on the duct housing accepts up to
12 AWG (ISO 4 mm2) wire.

Alarm: Two-wire: depends on control panel which

Standby: Two-wire: 0.08 mA at 12 VDC;

must limit the alarm current to 100 mA
maximum
Four-wire: depends on detector base; refer to
pertinent base specifications

0.09 mA at 24 VDC
Four-wire: 24 mA at 12 VDC or 24 VDC

Environmental

Relative Humidity: Up to 93%, non-condensing

Temperature
(operating):

Radio Frequency
Interference
(RFI) Immunity:

+32°F to +100°F (0°C to +38°C)

No alarm or setup on critical frequencies in
the range from 26 MHz to 950 MHz at field
strengths less than 50 V/m

Mechanical

Color: Bone white

Dimensions
(diameter x D):

4 in. x 1.25 in. (10.2 cm x 3.2 cm)

Ordering information

D285DH Photoelectric Duct Smoke Detector Head
(12 VDC or 24 VDC)

Detects the large smoke particles which typically
result from wood, paper, and fabric combustion

Order number D285DH

Parts included

QuantityComponent

1 Detector head with dust cover

1 Lit pack – Installation Manual, Technical Service Note on

installation

Technical specifications

Electrical

RMS Ripple
(maximum):

Voltage (input): Two-wire: 8.5 VDC to 33 VDC

Current

25% of DC input

Four-wire: 10 VDC to 30 VDC