Conventional Fire Alarm Systems
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A conventional fire alarm system is a regularly used and the natural choice for smaller applications or where budget constraints exist. Conventional fire alarm system is economical and adaptable to a variety of applications, big or small, making it one of the most flexible fire alarm systems. The versatility and ease of installation, this alarm control system have power and can be easily configured for use within a wide range of industries.
In Conventional Fire Alarm System the 'intelligence' of the system resides solely within the Fire Alarm Control Panel.
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Panel receiving trigger signal from a Conventional Detector or Call Point and in turn, signals the condition to other devices such as alarm sounders and remote signalling equipment.
Conventional fire alarm systems can be built for complete building/facility fire alarm protection and for fire sprinkler, sprinkler pre-action deluge fire alarm applications.
Conventional detectors are normally connected to the Fire Control Panel via dedicated circuits, each circuit protecting a designated 'Zone' or 'Area' of the building (the maximum size of which will depend on regulations. |
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Conventional Ionisation Smoke Detectors
The Fire Control Panel will normally be arranged in a set number of Zones or Circuits, e.g. 1, 2, 4, 8 etc. and have 2 separate sounder circuits.
It can be used in areas where early warning of superheated or flaming combustibles is expected. Ionization smoke detector senses smoke and goes into alarm. A single radioactive source ionizes two chambers within the detector, a reference chamber, and the smoke sensing chamber. The air is ionized by this source and small DC current flows between the electrodes of each chamber. Smoke can freely enter the sensing chamber while the inner chamber is virtually sealed to smoke. Smoke entering the sensing chamber causes a reduction in the DC current flow, the voltage imbalance between the two chambers is proportional to the smoke density. When the voltage differences become great enough it causes the detector to go into alarm. The two chamber design is utilized to compensate for changes in atmospheric and environmental conditions.
Spacing
Spacing of smoke detectors is followed on the guidelines listed in NFPA 72 and also base the number and location of sensors on an engineering survey of the area to be detected.
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The heat detector operates by using a matched pair of thermostat to sense heat. One thermostat is exposed to the ambient temperature, the other is sealed. In normal conditions, the two thermostats register similar temperatures, but, on the development of a fire, the temperature recorded by the exposed thermostat will increase rapidly, resulting in an imbalance of the thermostats and causing the detector to change to the alarm state.
The multi-sensor uses the new optical technology in combination with a heat sensor to further extend its capabilities as a smoke detector.
Image Source:Apollo Detector
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