Silentknight SK-Duct Addressable Photoelectric Duct Detector User Manual download pdf (Page 3)

FIGURE 4.

DETECTOR

HOLE

12˝

2˝

NOTE: Air currents inside the duct may cause excessive vibration, especially

when the longer sampling tubes are used. In these cases, a 3-inch floor flange

(available at most plumbing supply stores) may be used to fasten the sam-

pling tube to the other side of the duct. When using the flange/connector

mounting technique, drill a 1 to 1¼-inch hole where the flange will be used.

[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 hous-

ing 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

section of this manual.

[6]MEASUREMENT TESTS

[6.1]AIR FLOW

The SK-Duct is designed to operate over an extended air speed range of 100

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

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)

*Must extend a minimum of

⁄3 the duct width

FIGURE 3. AIR DUCT DETECTOR SAMPLING TUBE:

SAMPLING TUBE ENDCAP

ARROW MUST FACE

INTO AIR FLOW

AIR FLOW

DIRECTION

CAUTION: The sampling tube end cap, included with the detector, is criti-

cal 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. In-

stall 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 acces-

sory 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 air-

flow first. Position the tube so that the arrow points into the airflow as

shown in Figure 3. 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.

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 op-

posite the hole already cut for the sampling tube. Ensure that the sam-

pling 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

⁄4˝ downward for every 12˝ of duct width per Figure 4.

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.

SK-300-000 3 I56-3432-001R

HIGH

LOW

9 VOLT

BATTERY

9 VOLT

BATTERY

9 VOLT

BATTERY

TO SAMPLING TUBE

TO EXHAUST TUBE

DIFFERENTIAL

PRESSURE

TRANSMITTER

MODEL #607-01

15 TO 36

VDC SUPPLY

1000 OHM 5%

1 WATT RESISTOR

VOLT METER FLUKE

MODEL 87 OR

EQUIVALENT

+ –

H0163-01

FIGURE 5. PROCEDURE FOR VERIFYING AIR FLOW:

H0215-00

H0551-00

1 2 3 4 5 6

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Silentknight SK-Duct Addressable Photoelectric Duct Detector User Manual Page 3

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