INSTALLATION AND MAINTENANCE INSTRUCTIONS
Air Duct Smoke Detector
Rectangular Footprint Dimensions:
Square Footprint Dimensions:
Operating Voltage Range:
Max . Alarm Current (LED on):
NOTE: The SK-Duct comes with the sensor head factory installed, part number SK-PHOTOR .
Table of Contents
 Field Wiring
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Read System Sensor's Applications Guide: Duct Smoke Detectors (HVAG53),
which provides detailed information on detector spacing, placement, zoning,
wiring, and special applications . Copies of this manual are available online
at www .systemsensor .com . NFPA Standards 72 and 90A should also be refer-
enced for detailed information .
NOTICE: This manual shall be left with the owner/user of this equipment .
IMPORTANT: This detector must be tested and maintained regularly following
NFPA 72 requirements . The detector must be tested an maintained regularly fol-
lowing NFPA 72 requirements . According to NFPA, the detector should be visu-
ally inspected semiannually and functionally tested at least once a year . This
may need to be more frequent depending on the air quality of the duct supply air .
 LIMITATIONS OF DUCT SMOKE DETECTORS
The National Fire Protection Association has established that DUCT DETEC-
TORS MUST NOT BE USED AS A SUBSTITUTE FOR OPEN AREA DETECTOR
PROTECTION as a means of providing life safety . Nor are they a substitute for
early warning in a building's regular fire detection system .
System Sensor supports this position and strongly recommends that the user
read NFPA Standards 90A, 72, and 101 . The SK-Duct Air Duct Smoke Detectors
are listed per UL 268A .
This device will not operate without electrical power . Fire situations may
cause an interruption of power . The system safeguards should be discussed
with your local fire protection specialist .
This device will not sense smoke unless the ventilation system is operating
and the cover is installed .
For this detector to function properly, it MUST be installed according to the
instructions in this manual . Furthermore, the detector MUST be operated within
ALL electrical and environmental specifications listed in this manual and the
sensor head installation manual . Failure to comply with these requirements may
prevent the detector from activating when smoke is present in the air duct .
-4° to 158°F (-20° to 70°C)
32° to 120°F (0° to 49°C) with module installed in the SK-Duct
-22° to 158°F (-30° to 70°C)
0% to 93% Relative Humidity Non-condensing
100 to 4000 ft ./min . (0 .5 to 20 .3 m/sec .)
14 .38 in L×5 in W×2 .5 in D (37 cm L×12 .7 cm W×6 .36 cm D)
7 .75 in L×9 in W×2 .5 in D (19 .7 cm L×22 .9 cm W×6 .35 cm D)
1 .8 pounds; 0 .82 kg
15 to 32 VDC
300 µA @ 24 VDC (one communication every 5 seconds with LED blink enabled)
6 .5 mA @ 24 VDC
 GENERAL DESCRIPTION
Smoke introduced into this air duct system will be distributed throughout the
entire building . Smoke detectors designed for use in air duct systems are used
to sense the presence of smoke in the duct .
Model SK-Duct Air Duct Smoke Detector utilizes photoelectric technology for
the detection of smoke . This detection method, when combined with an ef-
ficient housing design, samples air passing through the duct and allows detec-
tion of a developing hazardous condition . When sufficient smoke is sensed,
an alarm signal is initiated at the fire control panel monitoring the detector,
and appropriate action can be taken to shut off fans, blowers, change over air
handling systems, etc . These actions can facilitate the management of toxic
smoke and fire gases throughout the areas served by the duct system .
The SK-Duct incorporates a sensor cover tamper feature that provides a trou-
ble signal at the panel immediately if the cover is removed or improperly in-
stalled . Proper installation of the sensor cover removes the trouble condition .
If programmed with the system control panel, two LEDs on each duct smoke
detector light to provide local visible indication .
The SK-Duct provides a remote alarm output for use with auxiliary devices,
such as the RA400Z/RA100Z remote LED annunciator, as well as remote test
capability with the RTS451/RTS151 or RTS451KEY/RTS151KEY Remote Test
[2.1] DETECTOR FEATURE SET
- Utilizes plug-in head, part number SK-PHOTOR
- Sampling tubes install from front and rear
- Compatible with existing accessories
- Able to address detector per code switches on sensor head .
 CONTENTS OF THE DUCT SMOKE DETECTOR KIT
1 . Sensor/power board assembly and covers sensor head is factory installed
2 . Three #10 sheet metal screws for mounting
3 . Drilling template
4 . One sampling tube end cap
5 . One plastic exhaust tube
NOTE: A sampling tube must be ordered to complete the installation . It must
be the correct length for the width of the duct where it will be installed . See
Table 1 on page 3 to determine the inlet tube required for different duct widths .
 DETECTOR INSTALLATION
[4.1] VERIFY DUCT AIR FLOW DIRECTION AND VELOCITY
Model SK-Duct detectors are designed to be used in air handling systems hav-
ing air velocities of 100 to 4000 feet per minute . Duct widths from 6 inches to
12 feet can be accommodated . Be sure to check engineering specifications to
ensure that the air velocity in the duct falls within these parameters . If neces-
sary, use a velocity meter (anemometer) to check the air velocity in the duct .
12 Clintonville Road, Northford, CT 06472-1610
Phone: 203-484-7161 Fax: 203-484-7118
www .silentknight .com
ACCESSORY CURRENT LOADS AT 24 VDC
12 mA Max.
12 mA Max.
12 mA Max.