MN220 Series - 2-Wire Smoke Detectors - Instructions for Installation and Use

Sep 25, 2026

MN220 series two-wire photoelectric smoke detectors provide open-area protection for commercial and institutional fire alarm systems. The instructions cover key features such as advanced 90° photoelectric detection, RFI immunity to reduce false alarms, LED alarm indication, optional auxiliary Form C relay, and a fixed 57°C heat sensor option. Content explains how the detector operates, alarm indication states, sensitivity test behavior, reset timing, and operational limitations, plus guidance for locating units to ensure smoke reaches the chamber and avoid installation conditions that delay or prevent detection.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages4

Reading Time10 min

AccessFree to download

Features

Models

Introduction

How the Smoke Detector Works

Alarm Indications

Limitations of Smoke Detectors

Guidelines for Locating Smoke Detectors

MN220 Series 2-Wire Smoke Detectors INSTRUCTIONS FOR INSTALLATION AND USE 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 • Solid-state LED red Indicator Light • Optional auxiliary relay Form C • 57°C (135°F) fixed temperature heat sensor option • Magnet-activated Sensitivity Test Switch • Attractive styling for any decor • This symbol on the nameplate means that the product is listed by Underwriters Laboratories Inc. (UL Standard 268, Smoke Detectors for Fire Protective Signalling Systems.) ∗ Protected under Canadian patent No. 1452296. Other patents pending. Models MN220 MN220T MN220R MN220RT 2-Wire Detector 2-Wire Detector and Fixed Temp 57oC (135oF) Sensor 2-Wire Detector and Auxiliary Form “C” Relay 2-Wire Detector and Auxiliary Form “C” Relay and Fixed Temp 57oC (135oF) Sensor Introduction The DSC Meridian MN220 series smoke detectors are two-wire smoke detectors intended for open area protection. They are suited for commercial and institutional 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. It is very important that you understand how totest 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 detector will send an alarm signal to the control panel. The auxiliary relay, if equipped, is also activated on alarm. When the smoke clears from the chamber, the detector will remain latched in the alarm state until reset by turning off the power supply from the control panel. Units with the temperature sensor (T) option will activate an alarm indicator light and auxiliary relay to initiate an alarm atthe control panel also. When the high heat condition returns to normal, the detector will remain latched in the alarm state until reset from the control panel. Resetting is achieved by 2 seconds of power down. Alarm Indications Condition Alarm LED Aux Relay | No smoke or heat | Pulse every
40 s | Deactivated | | --- | --- | --- | | Smoke or heat | ON steady | Activated | | Sensitivity test functioning normally | ON
Steady | Activated | | Sensitivity test
insufficient sensitivity | Pulse every
40 s | Deactivated | | No smoke or heat but latched in alarm | ON
steady | Activated | Limitations of Smok

FAQs

What should be done before installing and using the Meridian MN220 smoke detector?

Read the instruction sheet thoroughly before installing and using the detector, and follow the installation and operation guidance to ensure proper connection and placement. Test the overall alarm system regularly using the test procedures in the system manual.

How does the smoke detector detect smoke and trigger an alarm?

A light beam is directed across the smoke chamber and normally not reflected into the sensor. When smoke enters, it scatters and reflects the light so the sensor detects sufficient light and activates the alarm indicator and sends an alarm signal to the control panel.

What are key limitations and placement guidelines to ensure reliable detection?

Detectors require power and only alarm when smoke enters the smoke chamber; obstructions and locations that prevent smoke entry can delay or prevent alarms. Place detectors at appropriate spacing (e.g., on smooth ceilings) and avoid dead air spaces near peaked or gabled ceilings and turbulent airflow near doors, fans, or windows.

Sep 25, 2026

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