Before Installing
Please thoroughly read this manual and applicable sections
of System Sensor’s Manual I56-506,
Guide for Proper Use of
Projected Beam Detectors
. Copies of this manual are avail-
able from System Sensor.
General Description
System Sensor Model 6424 is a long range projected beam
smoke detector designed to provide open area protection. It
is to be used with UL-listed, separately supplied power (4-
wire) control panels only. The detector consists of a sepa-
rate transmitter and receiver. Smoke entering the area
between the transmitter and receiver causes a reduction in
signal at the receiver. When the obscuration reaches one of
two predetermined thresholds (chosen with a switch in the
receiver), the detector generates an alarm signal. Complete
blockage of the beam causes a trouble signal to avoid false
alarms. Slow changes in obscuration due to a build up of
dirt or dust on the lens of the detector are compensated for
by a microcontroller which continuously monitors the sig-
nal strength and periodically updates the alarm and trouble
thresholds. When the self-compensation circuit reaches its
limit, the detector generates a trouble signal, indicating the
need for service.
Three LEDs at the receiver indicate the status of the detec-
tor: a red LED for alarm, a yellow LED for trouble, and a
pulsed green LED for standby operation. The alarm signal
latches and can be reset by a momentary power interrup-
tion, by using the remote reset input to the receiver if using
the remote test/reset station model RTS451, or with the lo-
cal reset button located behind the rear door in the receiver.
A trouble signal automatically resets upon removing the
cause of trouble. In addition to these indicators, there are
four LEDs on both the receiver and the transmitter which
are used as a beam alignment aid. No additional equipment
is needed for alignment of the beam.
Each detector contains one Form A (normally open) con-
tact for alarm signals and one Form B (normally closed)
contact for trouble signals. Supervision of power is accom-
plished by installing a Power Supervisory End-of-Line Relay
Module (model A77-716) at the end of the detector power
loop. When power is applied to and through the detectors,
the EOL Power Supervisory Module is energized. The relay
contacts, along with the detector’s trouble relay contacts,
can provide a closed series circuit in the control panel’s
alarm-initiating loop. A loss in power or a trouble condition
at the detector causes the respective EOL or trouble relay to
open, resulting in a trouble signal at the control panel.
Parts List
Description
Quantity
Receiver Unit
1
Transmitter Unit
1
Receiver Wiring Cable
1
Transmitter Wiring Cable
1
Wall Mounting Bracket
2
Ceiling Mounting Bracket (inside part)
2
Ceiling Mounting Bracket (outside part)
2
Wall Bracket Screw
2
Ceiling Bracket Screw
2
Washers
4
Allen Wrench
1
Instruction Manual
1
Test Filter
1
Cable Exit Plug
1
Hole Plug
1
Detector Placement
This section of the manual discusses the placement of pro-
jected beam detectors. Though this information is based
upon industry expertise, it is intended to be used only as a
technical guide. Always comply with the requirements of
applicable codes and standards such as, NFPA 72, National
Fire Alarm Code, as well as directives of the Authority Hav-
ing Jurisdiction (AHJ). For general information on the
placement of detectors, read System Sensor’s Manual I56-
506,
Guide for Proper Use of Projected Beam Detectors
.
Projected beam detectors are usually located with their
beams parallel to the ceiling. However, they can be
mounted vertically or at any angle to protect the area in-
volved. Since beam detectors sense the smoke buildup over
a distance, they are ideal for locations with high ceilings.
They can also be mounted on a wall or ceiling below the
level of a spot type detector, reducing the effects of air
stratification. Some typical locations would include large
areas with high ceilings such as atriums, warehouses, and
factories.
NOTE:
Projected beam smoke detectors should always be
mounted to stable mounting surfaces. See the
MOUNTING LOCATION section for details.
Some fire codes specify spacing on a given center-to-center
distance between detectors under ideal conditions. These
spacings are based on rooms with smooth ceilings and no
physical obstructions between the contents being protected
and the detectors. Moreover, they are also based on a maxi-
mum ceiling height, and on the assumption that the value
and the combustible nature of the contents of the room be-
ing protected do not warrant greater protection or closer
spacing.
D400-18-00
2
I56-494-10R
