MIRROR: G K Bhat
Fire Alarm hooter plays a significant role in fire safety. The hooters are connected to main fire control panel. When the detectors are activated, the hooters come up automatically. Most of the manufacturers design the fire alarm hooters in such a way that these devices play dual role as hooters as well as speakers. This is done to avoid multiple cabling and using two different devices as hooters and speakers.The device which plays dual role as hooter and speaker, when put on auto mode, when activated through activation of the detector, works a s hooter and raises the alarm,further, works as speakers by announcing the pre-recorded voice messages. If we put the system on manual mode, we can use these devices for announcing the warnings/instructions, by using them as “public Address System”
Manual call points is another device plays significant role in fire safety. Manual call point is a small device place at an interval of 30 meters all over the building. When anybody spots a fire or possible fire situation, one can use this device and alert the people. The device is like a small box . the front panel is simply a glass type cover (it is not glass ) by braking or lifting the front cover the communication goes to the fire control panel and the entire fire warning system is activated
As we discussed earlier, the primary purpose of Fire Alarm System is to provide an early warning of fire so that people can be evacuated and immediate action can be taken to stop the fire as soon as possible. The Fire Alarm System can also be integrated with AHU, AC supply, access control, Fire Fighting systems, BMS etc.,
The loopof addressable fire alarm system consists of devices like detectors, manual call points, Hooters, control panel etc. They are working on 24 volts DC, This power supply drawn from main control panel through 1 cable (2 core). “In case of fire” detector to panel and panel to hooters digital signals are sent through same cable. Using power line communication technique. Each and every devices like detectors, manual call points, hooter etc., are having unique address.
For example “In case of fire” the respective area detector senses the fire and sends the data of fire with detector number to fire control panel. On receipt of the signal the control panel display shows the exact zone number, zone location, device number and device location. Also the panel shall send signal to respective hooters, firefighting systems, HVAC tripping etc, If PC is connected with the monitor, the pops up will come on the screen with all the indications along with mimic layout, fire affected zone and device flashes. The major advantage of 1 cable fire alarm system is
- Pin points the fire affected location, so that the user can reach the spot at the earliest.
- Using just 1 cable entire devices (max – 255) can be connected. So that enormous amount of cabling is saved
- In normal case the cable length can be of 1 km, if required it can be extended up to 5 km using booster module.
- Conventional and wireless devices can be easily integrated.
The cabling can be done as shown below.
In the picture shown above, you can see various type of devices are connected to the loop. In this type of cabling design the different devices required to be used in fire detection system can be connected to a single loop. Therefore there is no requirement of different cabling for different devices.
In our next topic let us discuss about the fire control panels and techniques
G K Bhat