System Sensor DNRHS User Manual
WARNING
INSTALLATION AND MAINTENANCE INSTRUCTIONS
I56-3535-002R
DNRHS Intelligent
Air Duct Smoke Detector
SPECIFICATIONS
Length: 14.4 inches
Width: 5.0 inches
Depth: 2.9 inches
Weight: 1.6 pounds
Operating Temperature Range: 32° to 100°F (0° to 38°C)
Operating Humidity Range: 10% to 93% Relative Humidity
Duct Air Velocity: 300 – 4000 ft./min.
Voltage Range: 15 – 32 VDC Peak
Standby Current (nominal): 230uA at 24 VDC (no communication)
330uA at 24 VDC (one communication every 5 sec. with LED enabled)
LED current (nominal): 6.5mA at 24 VDC
Table of Contents Page
[1] Limitations of Duct Smoke Detectors .......................... 1
[2] General Description ...................................... 1
[3] Contents of the Duct Smoke Detector Kit .......................2
[4] Detector Installation ......................................2
[5] Sampling Tube Installation .................................3
[6] Measurement Tests .......................................3
[7] Field Wiring ............................................4
[8] Verification of Operation ...................................4
[9] Dectector Cleaning Procedures ..............................5
[10] Sensor Replacement .....................................5
Warranty ................................................. 6
BEFORE INSTALLING
Please thoroughly read System Sensor’s Guide for Proper Use of Smoke Detectors in Duct Applications (I56-473-XX), which provides detailed information
on detector spacing, placement, zoning, wiring, and special applications. Copies of this manual are available from System Sensor. NFPA Standards 72, 76,
and 90A should also be referenced for detailed information.
NOTICE: This manual should be left with the owner/user of this equipment.
All sensors must be tested after installation and periodically thereafter. Testing methods must satisfy the Authority Having Jurisdiction (AHJ). Sensors
offer maximum performance when tested and maintained in compliance with
NFPA 72.
FIGURE 1:
EXHAUST TUBE
[1]LIMITATIONS OF DUCT SMOKE DETECTORS
The National Fire Protection Association has established that DUCT DETECTORS 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 DNRHS 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.
[2] GENERAL DESCRIPTION
An HVAC system supplies conditioned air to virtually every area of a building.
Smoke introduced into this air duct system will be distributed to the entire
building. Smoke detectors designed for use in air duct systems are used to
sense the presence of smoke in the duct. In facilities with large air changes per
hour, airflow can carry smoke particles directly to the HVAC system. Per NFPA
76 Very Early Warning Fire Detection (VEWFD) sensors shall be installed to
monitor return air from the space. The DNRHS can be installed to monitor the
return air from the space in order to meet NFPA 76 requirements.
3825 Ohio Avenue, St. Charles, Illinois 60174
1-800-SENSOR2, FAX: 630-377-6495
www.systemsensor.com
WIRING COMPARTMENT
SAMPLING
TUBE
SOLD
SEPERATELY
SENSOR MODULE
NOTE: SENSOR HEAD IS ONLY
INCLUDED ON SPECIFIED MODELS.
SENSOR HEAD
WIRING COMPARTMENT COVER
SENSOR MODULE COVER
H0569-06
SS-400-006 1 I56-3535-002R
The DNRHS Air Duct Smoke Detector uses a 7251 laser smoke sensor. This
REPLACE SCREW
smoke detection method combined with an efficient housing design that
samples air passing through a duct provides early detection 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 and blowers, change over air handling systems,
etc. This can prevent the distribution or isolation of toxic smoke and fire gases
throughout the areas served by the duct system as well as provide an alert of
a developing hazardous condition in a facility.
Two LEDs on each detector latch ON to provide a local alarm indication. There
is also a remote alarm output for use with auxiliary devices. The DNRHS
has remote test capability with the RTS451/RTS151/RTS451KEY/RTS151KEY
Remote Test Station.
[2.1] DETECTOR FEATURE SET
– Utilizes plug-in head
– Sampling tubes install from front and rear
– Compatible with existing accessories
– Able to address detector per code switches on sensor head.
[3] CONTENTS OF THE DUCT SMOKE DETECTOR KIT
1. Sensor/power side and covers (use appropriate sensor per the system
control panel)
2. Three #10 sheet metal screws for mounting
3. Drilling template
4. One sampling tube end cap
5. One plastic exhaust tube
6. Laser Smoke Sensor
8. DCOIL Test Coil
[4] DETECTOR INSTALLATION
FIGURE 2. APPLICATION EXAMPLES:(VIEWED FROM ABOVE)
3ft
2ft
CENTER
1
“LENGTH”
2
1
2ft
TYPIC
7ft
3
2
C0931-00
NOTE: A DST 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.
[4.1]VERIFY DUCT AIR FLOW DIRECTION AND VELOCITY
Model DNRHS detectors are designed to be used in air handling systems having air velocities of 300 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 necessary, use a velocity meter (anemometer) to check the air velocity in the duct.
Each DNRHS duct smoke detector should be mounted as follows:
FIGURE 3. PLENUM DIMENSION AND DETECTOR POSITION:
(VIEWED FROM SIDE)
H0-616-00
1. Location: Mount detector on the room side (up stream) of any air filter.
NOTICE: Mounting detector after filter may filter out smoke particles and
is not recommended.
2. Coverage: Each detector pipe length should be mounted along the longer
direction of the return air opening (length direction). One detector and
one standard, pre-drilled pipe length should be installed for every 2ft
of return air opening width. When more than one detector is required
(widths greater than 2ft.), detector housings should be staggered on opposite ends of the opening length. (refer to Figure 2).
3. Install detectors at the proper height within the duct/plenum per the
recommendations shown in Figure 3.
4. Hole Direction: holes facing directly into flow for positive pressure effect
5. Ensure adequate pressure differential across the detector housing according to section 8.1 of this document.
FIGURE 4
REMOVE SCREW AND PIVOT
DETECTOR AS SHOWN BELOW.
[4.2]DETERMINE MOUNTING LOCATION AND CONFIGURATION
TO SECURE DETECTOR
IN PLACE.
H0-550-00
On ducts wider than 18 inches it is recommended that the detector be
mounted downstream of a bend, obstruction in the duct, or the supply or
return air inlet.
Exception: Installation of duct detectors can be on or within a commercial
packaged rooftop heating and air-conditioning system, fire/smoke dampers
and economizers. They may be mounted in either the supply and/or return air
section as determined by local code.
Once a suitable location is selected, determine if the detector is to be mounted
in a side-by-side “rectangular” configuration or a top-over-bottom “square”
configuration as shown in Figure 4. If mounting in the square configuration,
remove the rear attachment screw, rotate the unit at hinge, and replace the
screw into the new attachment hole as shown in Figure 4. Do NOT remove
the hinge screw during this process. Final installation approval shall be based
upon passing differential pressure and smoke entry tests described in the Measurement Tests section.
[4.3]DRILL THE MOUNTING HOLES
Remove the paper backing from the mounting template supplied. Affix the
template to the duct at the desired mounting location. Make sure the template
lies flat and smooth on the duct.
[4.3.1]FOR RECTANGULAR SIDE-BY-SIDE MOUNTING CONFIGURATION:
Center punch at (4) target centers: (2) “A” for sampling tubes and (2) “B” for
the rectangular configuration mounting tabs as shown on mounting template.
Drill pilot holes at target “A” centers and cut two 1.375 inch diameter holes
using a 13⁄8-inch hole saw or punch. Drill .156 inch diameter holes using a 5⁄32
inch drill at target “B” centers.
[4.3.2]FOR SQUARE TOP-OVER-BOTTOM MOUNTING CONFIGURATION:
Center punch at (4) target centers: (2) “A” for sampling tubes and (2) “C” for
the square configuration mounting tabs as shown on mounting template. Drill
pilot holes at target “A” centers and cut two 1.375 inch diameter holes using
a 13⁄8-inch hole saw or punch. Drill .156 inch diameter holes using a 5⁄32 inch
drill at target “C” centers. If desired, drill an additional .156 inch hole at the
location of one of the mounting tabs on the lower housing.
SS-400-006 2 I56-3535-002R
[4.4]SECURE THE DUCT DETECTOR TO THE DUCT
CAUTION
WARNING
TO SAMPLING TUBE
Use two (rectangular configuration) or three (square configuration) of the provided sheet metal screws to screw the duct detector to the duct.
CAUTION: Do not overtighten the screws.
Do not overtighten the screws.
[5]SAMPLING TUBE INSTALLATION
[5.1]SAMPLING TUBE SELECTION
The sampling tube must be purchased separately. Order the correct length, as
specified in Table 1, for width of the duct where it will be installed. The sampling tube length must extend at least 2/3 across the duct width for optimal
performance.
The sampling tube is always installed with the air inlet holes facing into the
air flow. To assist proper installation, the tube’s connector is marked with an
arrow. Make sure the sampling tube is mounted so that the arrow points into
the airflow as shown in Figure 5. Mounting the detector housing in a vertical
orientation is acceptable provided that the air flows directly into the sampling tube holes as indicated in Figure 5. The sampling tube and exhaust tube
can be mounted in either housing connection as long as the exhaust tube is
mounted downstream from the sampling tube.
TABLE 1. SAMPLING TUBES RECOMMENDED FOR
DIFFERENT DUCT WIDTHS:
Outside Duct Width Sampling Tube Recommended*
Up to 1 ft. DST1
1 to 2 ft. DST1.5
2 to 4 ft. DST3
4 to 8 ft. DST5
8 to 12 ft. DST10 (2-piece)
2
*Must extend a minimum of
FIGURE 5. AIR DUCT DETECTOR SAMPLING TUBE:
CAUTION: The sampling tube end cap, included with the detector, is critical
to proper operation of the duct smoke detector. The end cap is needed to
create the proper air flow to the sensor of the duct smoke detector. Once any
sampling tube length adjustments are made, plug the end of the sampling
tube with the provided end cap.
A plastic exhaust tube is included with the unit to be installed if needed. Install into the housing connection that is downstream from the sampling tube
connection. The exhaust tube can be installed from the front of the detector
or the back. A longer 1 foot exhaust tube, model ETX, is available as an accessory in cases where the molded exhaust tube does not extend at least 2 inches
into the duct.
[5.2]SAMPLING TUBE INSTALLATION
1. For tubes shorter than the width of the duct, slide the sampling tube,
with installed end cap, into the housing connection that meets the airflow first. Position the tube so that the arrow points into the airflow as
shown in Figure 5. Per NFPA sampling tubes over 3 feet long should be
supported at the end opposite of the duct detector. In ducts wider than 8
feet, work must be performed inside the duct to couple the other section
of the sampling tube to the section already installed using the ½ inch
conduit fitting supplied. Make sure that the holes on both sections of the
air inlet sampling tube are lined up and facing into the airflow.
⁄3 the duct width
SAMPLING TUBE ENDCAP
ARROW MUST FACE
INTO AIR FLOW
AIR FLOW
DIRECTION
HO-551-00
2. For tubes longer than the width of the air duct, the tube should extend
out of the opposite side of the duct. Drill a ¾ inch hole in the duct opposite the hole already cut for the sampling tube. Ensure that the sampling tube is angled downward from the duct smoke detector to allow for
moisture drainage away from the detector. The sampling tube should be
angled at least 1⁄4” downward for every 12” of duct width. There should
be 10 to 12 holes spaced as evenly as possible across the width of the
duct. If there are more than 2 holes in the section of the tube extending
out of the duct, select a shorter tube using Table 1. Otherwise, trim the
tube to leave approximately 1 to 2 inches extending outside the duct.
Plug the end with the end cap and tape closed any holes in the protruding section of the tube. Be sure to seal the duct where the tube protrudes.
In no case should more than 2 air inlet holes be cut off the tube. There must
be a minimum of 10 holes in the tube exposed to the air stream.
[5.3]MODIFICATIONS OF SAMPLING TUBES
There may be applications where duct widths are not what is specified for the
installation. In such cases, it is permissible to modify a sampling tube that is
longer than necessary to span the duct width.
Use a 0.193-inch diameter (#10) drill and add the appropriate number of holes
so that the total number of holes exposed to the air flow in the duct is 10 to 12.
Space the additional holes as evenly as possible over the length of the tube.
CAUTION: This procedure should only be used as a temporary fix. It is not
intended as a permanent substitute for ordering the correct length tubes.
[5.4]REMOTE SAMPLING TUBE INSTALLATION
The detector arrangement can also incorporate the remote mounting of the
sampling tube and/or exhaust tube. In this case both the detector, sampling
tube and exhaust tube (if included) should be rigidly mounted to withstand
the pressure and vibrations caused by the air velocity. The location of the
detector’s sampling tube should be such that there is uniform airflow in the
cross section area.
Pressure differential across the sampling and exhaust ports in the detector housing shall be verified to be between 0.01 and 1.11 inches of water. Do so by measuring the pressure difference between the inlet and outlet ports on the detector
housing using a manometer as described in the Measurement Tests sectiont of
this manual.
[6]MEASUREMENT TESTS
[6.1]AIR FLOW
The DNRHS is designed to operate over an extended air speed range of 300
to 4000 FPM. To verify sufficient sampling of ducted air, turn the air handler
on and use a manometer to measure the differential pressure between the two
sampling tubes. The differential pressure should measure at least 0.01 inches
of water and no more than 1.11 inches of water. Because most commercially
available manometers cannot accurately measure very low pressure differentials, applications with less than 500 FPM of duct air speed may require one
of the following: 1) the use of a current-sourcing pressure transmitter (Dwyer
Series 607) or 2) the use of aerosol smoke, see below for test descriptions.
[6.2]LOW FLOW AIR FLOW TEST USING DWYER SERIES 607
DIFFERENTIAL PRESSURE TRANSMITTER
Verify the air speed of the duct using an anemometer. Air speed must be at
least 300 FPM. Wire the Dwyer transmitter as shown in Figure 5. Connect the
leads of the meter to either side of the 1000Ω resistor. Allow unit to warm up
FIGURE 6: PROCEDURE FOR VERIFYING AIR FLOW
TO EXHAUST TUBE
HIGH
LOW
DIFFERENTIAL
PRESSURE
TRANSMITTER
MODEL #607-01
15 TO 36
VDC SUPPLY
9 VOLT
BATTERY
1000 OHM 5%
1 WATT RESISTOR
VOLT METER FLUKE
MODEL 87 OR
EQUIVALENT
+–
9 VOLT
BATTERY
9 VOLT
BATTERY
HO-163-01
SS-400-006 3 I56-3535-002R
Loading...