Fire Alarm System Types 3s6t4e

FIRE ALARM SYSTEM TYPES There are two general types of fire alarm systems in use, these are 1. Conventional (traditional) 2. Addressable type

FIRE ALARM SYSTEM TYPES Conventional System Conventional fire alarm systems use simpler technology and are suited to smaller applications where they are more cost effective than an addressable system. A conventional fire alarm system may use fire detection zones, which are usually represented by LEDs on the control . Each zone identifies a specific area of the building in order to speed up the location of a fire. Each zone is made up of a group of Automatic Fire Detectors and Manual Call Points. In the event of a fire being detected either automatically or manually, the system control will then operate the alarm. In this type of system the physical wiring dictates the zoning and the detector decides if it’s a fire condition or not.

FIRE ALARM SYSTEM TYPES Addressable Fire Alarm System Addressable fire alarm systems, and their corresponding control s, are more advanced than their conventional counterparts and offer a higher degree of programming flexibility and single point detection. The system can be configured to provide a wide range of flexibility, with components controlling a variety of devices. This works by each device in the system having its own ‘address’, allowing the control to monitor and control the state of each individual device connected to it.

FIRE ALARM SYSTEM TYPES Conventional

Addressable

 Lower initial equipment costs.  Easier to install.  Defined location of fire/alarm  More system status not provided at the or information at the and central station central station.  Can be easier to program.  Input/Output programming  Limited expansion capability. much more flexible.  Usually much more room available to expand

Alarm Initiating Device Alarm Initiating Device These are the devices intended to respond to any number of detectable physical changes associated with fire convected thermal energy.

Alarm Initiating Device 1. Smoke Detector A smoke detector is a device that senses smoke, typically as an indicator of fire. Commercial security devices issue a signal to a fire alarm control as part of a fire alarm system, while household smoke detectors, also known as smoke alarms, generally issue a local audible or visual alarm from the detector itself. Two Basic Types a. Photoelectric - It uses a photocell coupled with a specific light source. It is basically a smoke detector chamber which causes an alarm signal whenever a smoke enters the detector resulting to disrupts the light beam inside the device. b. Ionization – It works whenever an invisible product of combustion enters the chamber which leads to decrease the current between –ve and + ve plates thereby initiating a signal. It generally responds faster to flaming fires versus smoldering fires.

Alarm Initiating Device 2. Flame detector A flame detector is a sensor designed to detect and respond to the presence of a flame or fire. Responses to a detected flame depend on the installation, but can include sounding an alarm, deactivating a fuel line (such as a propane or a natural gas line), and activating a fire suppression system. Three Basic Types a. Ultraviolet light (UV) – It works by detecting the UV radiation emitted at the instant of ignition. . b. Infrared (IR) – It monitors the infrared spectral band for specific patterns given off by hot gases. It requires the flickering motion of a flame c. UV/IR - These detectors are sensitive to both UV and IR wavelengths, and detect flame by comparing the threshold signal of both ranges. This helps minimize false alarms.

Alarm Initiating Device 3. Heat Detector A heat detector fire alarm device is designed to respond when the convected thermal energy of a fire increases the temperature of a heat sensitive element. Two Basic Types a. Fixed temperature heat detectors – It is the most common type of heat detector. Fixed temperature detectors operate when the heat sensitive eutectic alloy reaches the eutectic point changing state from a solid to a liquid. b. Rate-of-Rise (ROR) heat detectors – It operates on a rapid rise in element temperature of 12° to 15°F (6.7° to 8.3°C) increase per minute, irrespective of the starting temperature.