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P/N 315-049708FA-4

2

APPLICATION

The 8741, 8742 and 8743 duct smoke detectors provide early
detection of smoke and products of combustion present in
air moving through an HVAC duct supply, return, or both.
These devices are designed to prevent the recirculation of
smoke in areas by the air handling system’s fans and blow-
ers. Complete systems may be shut down in the event of
smoke detection.

For the correct installation of a duct smoke unit please refer

to NFPA 72 (National Fire Alarm Code), NFPA 90A (Standard

for Installation of Air Conditioning and Ventilation Systems),

NFPA 70 (National Electrical Code) and NFPA 92A (Recom-

mended Practice for Smoke Control Systems).

OPERATION

When the Models 8741, 8742 and 8743 are operating, a
sample of air is drawn from the duct and passed through the
sampling chamber by means of the input sampling tube. The
air sample passes through the smoke detector mounted in
the duct housing and is exhausted back into the duct
through the outlet tube.

This detector is equipped with cover removal switch (SW1) that
instantly provides a trouble condition upon removal of the clear
cover. For all testing and inspection with the cover removed, the
cover removal switch (designated as SW1 on PCB) must be
manually depressed to simulate normal operation.

LED Indicator

The 8741, 8742 and 8743 contain an LED indicator (located on
the smoke detector) capable of flashing either one of three
distinct colors: green, yellow, or red. During each flash interval,
the microprocessor based detector checks the following:

for smoke in its sensing chamber

that its critical smoke sensing electronics are operating.

Based on the results of these checks, the LED indicator
flashes as follows:

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Summary of Contents for 8742

Page 1: ...c see char har har har harts on the page ts on the page ts on the page ts on the page ts on the page 1 1 1 1 12 of this manual 2 of this manual 2 of this manual 2 of this manual 2 of this manual TECHN...

Page 2: ...detector is equipped with cover removal switch SW1 that instantly provides a trouble condition upon removal of the clear cover For all testing and inspection with the cover removed the cover removal...

Page 3: ...R PLENUM FRESH AIR INTAKE DAMPER D D Figure 1 Typical Mounting of Duct Housing OUTLET TUBE INPUT SAMPLING TUBE CENTER LINE OF DUCT C L MOUNTINGTHE AIR DUCT HOUSING Location on Duct System This guideli...

Page 4: ...m of filters fires occurring in the filters will be detected but if the filters become blocked insufficient air flow through the duct unit will prevent the correct operation of the duct detector Duct...

Page 5: ...be cut to length and must span at least 80 the width of the duct Sampling tubes over 3 0 must be supported on the opposite side of the duct To ensure the correct operation the red stopper stopper in i...

Page 6: ...d the duct unit assembly in position and use 2 12 X 3 4 sheet metal screws packaged in the installation kit to secure the duct smoke detector to the HVAC duct sheet metal Air Duct Sampling Tube Pressu...

Page 7: ...e loop Note any limitations on the number of detectors and restrictions on the use of remote devices permitted for each circuit When replacing a detector with a different model be aware that existing...

Page 8: ...the initiating circuit 3 Do not use looped wire under base terminal 4 Break wire run to provide supervision of connection 5 The green grounding screw in the wiring compartment of the air duct housing...

Page 9: ...6 or 5 TB3 5 or 6 TB1 1A TB1 TB1 TB1 MODEL 8741 MODEL 8743 MODEL 8743 8710 8713 OPTIONAL REMOTE ALARM INDICATOR MODEL 8727C OR 8727W SEE NOTE 2 LOOP WIRES SEE COMPATIBLE CONTROL EQUIPMENT TABLE 8710 8...

Page 10: ...zle model AD TGN purchased separately available from Siemens Industry Inc insert the test gas nozzle into the hole in the red test plug in the unit cover Press can against cover for about 1 2 second t...

Page 11: ...F ed Farada arada arada arada araday S y S y S y S y Service R ervice R ervice R ervice R ervice Represent epresent epresent epresent epresentat at at at ati i i i ive ve ve ve ve If the fire alarm sy...

Page 12: ...P M 0 0 0 6 C P M 5 A F 0 5 8 4 3 0 5 1 3 N P 1 0 4 W L 3 A F 7 9 9 5 9 0 5 1 3 N P 1 0 4 W L A 4 E Z W L 4 A F 8 1 0 6 9 0 5 1 3 N P 1 0 4 W L A 8 E Z W L 3 A F 2 2 0 6 9 0 5 1 3 N P R O T C E T E D...

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