Limitations of Smoke Detectors
While the Meridian Smoke Detector has been designed for reliability,
it is important to know that all smoke detectors have limitations.
• Smoke detectors will not work without power. Devices powered
from a control panel will not function if the control panel’s AC and
battery backup power supplies both fail.
• Smoke detectors can only generate an alarm when smoke gets
inside the Smoke Chamber; anything that prevents smoke from
entering the Smoke Chamber may prevent or delay an alarm.
Refer to the Guidelines for Locating Smoke Detectors on this
Instruction Sheet; it is important that smoke detectors be located
on at least every floor of the premises, preferably in every room. It
is also important to avoid obstructions, such as closed doors, that
may prevent smoke from reaching the unit. A smoke detector will
not detect a fire in the walls, in the chimney or on the roof of a
building until smoke enters the Smoke Chamber.
• Smoke detectors have certain obvious limitations: they may not
provide protection for someone smoking in bed, for children playing
with matches, or for sudden and violent explosions. A smoke
detector is a single part of overall fire safety precautions; the smoke
detector should never be seen as a substitute for a complete fire
safety program.
Guidelines for Locating Smoke Detectors
On smooth ceilings, detectors may be spaced 9.1m (30 feet) apart
as a guide. Other spacings may be required depending on ceiling
height, air movement, the presence of joists, uninsulated ceilings,
etc. Consult NFPA 72 (1993), CAN/ULC-S553-M86 or other appropriate
national standards for installation recommendations.
Do not locate smoke detectors at the top of peaked or gabled
ceilings; the dead air space in these locations may prevent the unit
from detecting smoke.
Avoid areas with turbulent air flow, such as near doors, fans or
windows. Rapid air movement around the detector may prevent
smoke from entering the unit.
Do not locate detectors in areas of high humidity.
Do not locate detectors in areas where the temperature rises above
38
o
C (100
o
F) or falls below 5
o
C (41
o
F).
INSTRUCTIONS FOR
INSTALLATION AND USE
M N - 2 4 0 S E R I E S D C - P O W E R E D S M O K E D E T E C T O R S
Smoke in the Smoke Chamber deflects light
into the light sensor, triggering an alarm.
It is very important that you understand how to test and maintain your
system. Refer to the Instruction or User Manual for your alarm system,
and familiarise yourself with how the Fire Alarm functions of your
system operate. Be sure to test your system regularly following the
test procedures described in your manual. If you should ever have
problems operating or testing your system, and especially if there are
problems with the Fire Alarm functions, contact your Smoke Detector
Installer or Dealer immediately for service.
While smoke detectors and alarm systems are designed to warn you
of potentially dangerous situations, no system can prevent
emergencies. An alarm system is not a substitute for life and property
insurance; you should always maintain appropriate insurance
coverage.
How the Smoke Detector Works
As shown in the illustration, a light source is directed across the
smoke chamber and is not normally reflected into the sensing
element. When smoke enters the chamber, the light beam is
scattered by the smoke and is reflected into the sensor. When
enough light is detected by the sensor, an alarm is activated. On
alarm, the Alarm Indicator Light will come ON and the Alarm Relay is
activated to send an alarm signal to the control panel. The Sounder
and the Auxiliary Relay, if equipped, are also activated on alarm.
When the smoke clears from the smoke chamber, the unit will
only reset the Sounder. The Relay(s) and Indicator Light will
remain in the alarm state until reset by turning off the power
supply from the control panel.
Alarm Indications
Condition
Alarm LED
Relay(s)
Sounder
(if equipped)
No Smoke or Heat
Pulse every
Deactivated
Silent
40 s
Smoke or Heat
ON steady
Activated
Alarm
Automatic Self Test
Pulse every
Deactivated
Silent
Functioning Normally
40 s
Automatic Self Test
Pulse every
Deactivated
Chirp every
Insufficient Sensitivity
40 s
40 s
Sensitivity Test
ON
Activated
Alarm
Functioning Normally
Steady
Sensitivity Test
Pulse every
Deactivated
Silent
Insufficient Sensitivity
40 s
No Smoke or Heat
ON
Activated
Silent
but Latched in Alarm
steady
READ THIS INSTRUCTION SHEET THOROUGHLY BEFORE
INSTALLING AND USING YOUR MERIDIAN SMOKE DETECTOR
Features
• Advanced 90° photoelectric detection pattern and specially
designed smoke chamber
∗∗∗∗∗
for superior detection and dust
resistance
• Unique high signal-to-noise ratio and superior RFI immunity to
prevent false alarms
• Excellent smoke access provides reliable detection for all
smoke flow directions and velocities
• Optional Loud 85dB piezoelectric alarm horn
• Solid-state LED red Indicator Light
• Form A (normally opened, alarm closed) alarm relay (standard);
optional Form C (normally opened/normally closed) auxiliary
relay
• 57°C (135°F) fixed temperature heat sensor option
• Magnet-activated Sensitivity Test Switch
• The unit will automatically perform a self-test once every 40
seconds and provide an audible trouble indication (in sounder-
equipped units) if the unit has insufficient smoke sensitivity
• Attractive styling for any decor
• ULC listed S529
∗∗∗∗∗
Protected under Canadian Patent No. 1452296. Other patents pending.
Models
MN240
Form “A” Alarm Relay
MN240T
Form “A” Alarm Relay and Fixed Temp (57
o
C) Sensor
MN240R
Form “A” Alarm Relay and Auxiliary Form “C” Relay
MN240RT
Form “A” Alarm Relay and Auxiliary Form “C” Relay
and Fixed Temp (57
o
C) Sensor
MN240S
Form “A” Alarm Relay and Sounder
MN240ST
Form “A” Alarm Relay and Sounder and Fixed Temp
(57
o
C) Sensor
MN240SR
Form “A” Alarm Relay and Sounder and Auxiliary
Form “C” Relay
MN240SRT
Form “A” Alarm Relay and Sounder and Auxiliary
Form “C” Relay and Fixed Temp (57
o
C) Sensor
Introduction
The DSC Meridian MN 240 Series Smoke Detectors are four-wire
smoke detectors intended for open area protection. They are suited
for commercial, institutional and residential fire alarm systems.
The DSC Meridian Photoelectric Smoke Detector incorporates many
advanced design features to provide years of reliable operation. It
is important to follow the Installation and Operation instructions on
this sheet to ensure that the unit will function properly — even the
best designed smoke detector will be rendered useless if it is not
connected or located properly.
Normally, light pulses in the Smoke Chamber
do not reach the light sensor
Testing Your Smoke Detector
Never use burning or
smouldering materials
to test a smoke detector.
Also, do not use high
pressure aerosols to
test smoke detectors.
The use of burning
materials or high
pressure aerosols can
give misleading and
meaningless results.
Test the detector for
minimum sensitivity by activating the test feature. To test the unit,
hold the test magnet against the case as shown below. The Alarm
Indicator Light will come ON, the Alarm Relay will be activated, the
Sounder (if equipped) will sound, and the alarm control panel
should indicate a fire alarm. When the magnet is removed, the
Sounder will be silenced, but the Alarm Light and Relay will remain
ON. Turn off the voltage supply to the detector for two seconds to
reset the detector to normal.
If the smoke detector does not function properly, call your Smoke
Detector Installer or Dealer for service.
Smoke Sensitivity may be measured in a correlated UL217 or CAN/
ULC S529-M87 smoke box. DSC will conduct this test for a nominal
charge. If a returned unit is found outside of its marked sensitivity
range, DSC will clean and restore the unit’s sensitivity to its marked
range.
Smoke sensitivity of installed detectors can be measured without
removal with the Gemini Model 501 Aerosol Smoke Detector
Analyzer. Follow the instructions supplied with the instrument. Start
with the sensitivity corresponding to the lowest marked detector
sensitivity; no alarm should be indicated. Reset with the highest
sensitivity setting; an alarm should then be indicated. These results
indicate that the unit is within its marked sensitivity range. Other
settings can be tried to bracket the detector’s sensitivity to a
narrower sensitivity range, such as may be important during annual
tests to quantify any change over time.
Owner’s Maintenance Instructions
The Meridian Smoke Detector is designed to require a minimum of
maintenance. If the case becomes dusty, wipe the case gently with
a soft dry cloth. If the case is greasy, wipe the case gently with a soft
cloth slightly dampened with soapy water.
Never disassemble the smoke detector; there are no user
serviceable parts inside the unit. Never paint the unit, as paint
may prevent smoke from entering the unit. If you are planning
renovations or repainting, contact your Installer and ask that the
unit be temporarily removed until work is complete.
Figure 2
Bedroom
Bedroom
Bedroom
Living
Room
Kitchen
Dining
Room
Family Room
Figure 1
Bedroom
Bedroom
Bedroom
Living Room
Kitchen
Smoke detectors should always be installed in accordance with NFPA 72, the
National Fire Alarm Code. Smoke detectors should always be located in
accordance with Paragraph 2.1.1.1 of NFPA 72, Chapter 2.:
“2-2.1.1.1 Smoke detectors shall be installed outside of each separate
sleeping area in the immediate vicinity of the bedrooms and on each additional
story of the family living unit, including basements and excluding crawl spaces
and unfinished attics. In new construction, a smoke detector also shall be
installed in each sleeping room.”
Figure 4
Figure 3
Bedroom
Bedroom
Basement
Living
Room
Dining
Room
NEVER
HERE
Acceptable
here
Top of detector
acceptable here
12"
(0.3m)
Max.
4"
(0.1m)
Max.
4"
(0.1m)
Ceiling
Wall
NOTE: Measurements shown are to
the closest edge of the detector.
