System Sensor DNRHS - Manual (Page 2)

SS-400-006 2 I56-3535-002R
[4.1]VERIfy DuCT aIR fLOw DIRECTIOn anD VELOCITy
Model DNRHS detectors are designed to be used in air handling systems hav-
ing 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 neces-
sary, use a velocity meter (anemometer) to check the air velocity in the duct .
Each DNRHS duct smoke detector should be mounted as follows:
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 op-
posite 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 accord-
ing to section 8 .1 of this document .
[4.2]DETERmInE mOunTInG LOCaTIOn anD COnfIGuRaTIOn
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 Mea-
surement 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 1
3 ⁄
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 1
3 ⁄
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 .
C0931-00
3ft
1
2ft
CENTER
7ft
2ft
2
1
2
3
“LENGTH”
TYPIC
fIGuRE 2. aPPLICaTIOn EXamPLES:(VIEwED fROm aBOVE)
The DNRHS Air Duct Smoke Detector uses a 7251 laser smoke sensor . This
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 ini-
tiated 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
H0-616-00
fIGuRE 3. PLEnum DImEnSIOn anD DETECTOR POSITIOn:
(VIEwED fROm SIDE)
H0-550-00
REMOVE SCREW AND PIVOT
DETECTOR AS SHOWN BELOW.
REPLACE SCREW
TO SECURE DETECTOR
IN PLACE.
fIGuRE 4
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 .