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Fire Alarm System Wiring

Posted January 24th, 2024

Fire Alarm System Wiring and How to Install Fire Alarm Equipment

In this article, we are trying to familiarize you with how to wire the fire alarm, how to test the zone or circuits of detectors and chassis, how to test the siren circuit and control panel of the fire alarm system. 

It is worth mentioning that by reading this tutorial, you can become an expert in troubleshooting and fixing fire alarm wiring. 

To start the work, we must first study the map of the fire alarm system and execute the wiring of the fire alarm system according to the map, and if the wiring is already implemented, match the implemented wiring with the map and correct it if there is any problem in it. 

In general, you can use a two-wire sprinkler cable for the circuit of sirens and detectors, and in buildings where LED remotes are used, you can use a three-wire cable with a cross section of 1.5 or 2.5 square millimeters. If the length of the cable route in each zone is less than 1000 meters, a cable with a cross section of 1.5 mm square is used.

Cables must be mechanically protected in places where there is a possibility of being hit or worn andchewed by animals. In the case of wires for sirens and lights, for protection, they can be built into the wall under at least 12 mm of plaster. 

The type of signal cable is determined according to the place where the cable passes, if the cable passes through areas with high noise, such as high voltage power cable or telecommunication cables, in this case, shielded cable is used, and otherwise, normal cable is used. The signal cable facing or inside the pipe should have the power to withstand fire for 30 minutes.

After wiring, we install detectors, chassis, and horns. 

Fire alarm detectors have positive and negative polarity, and in each circuit or zone, we can have thermal, smoke and chassis detectors in each part of the circuit the first, middle and last of the circuit. The wiring of the fire alarm detectors is done in parallel, and the detectors must be placed one behind the other and there should not be any branching in the circuit, and we install the element at the end of the EOL line on the base of the last piece which can be the chassis or the detector. 

The total number of smoke and heat detectors in each zone can be a maximum of 32 according to the BS standard. But to determine the number of detectors in each zone, refer to the manual of the same company.

Also, there is no limit to the number of chassis in each zone.

The wiring of the fire alarm buttons in conventional and addressable systems is almost the same, and in both systems, two wires enter the button, and the other two wires exit from it. It is not necessary to observe the positive and negative polarity, and to connect the input and output wires. On the terminals inside the thumb, it should be done according to the manufacturer's instructions. 

The sirens also have positive and negative polarity in the fire alarm system, and their circuit is parallel, and in the last siren, the element at the end of the line is installed, and there should never be a branch in its circuits, then we test the circuit of the sirens with an ohmmeter. so that we have exactly the resistance value of the end of the line on both ends of the wire at the beginning of the sirens route. 

When all the construction works are finished and there is no dust, we will install the central control panel in the designated place according to the plan and remove the cover on the detectors. 

The fire alarm panel should be installed in a place that can be easily seen. 

The place of installation of the fire alarm panel is usually in the main entrances or the routes where the firemen can enter. 

The fire alarm panel should be protected by a detector mounted on the ceiling and located directly above it, and there should be a main siren next to this control center. 

And after making sure that the circuit of detectors and sirens are healthy, we will install their wires according to the positive and negative polarity in the corresponding place in the fire alarm control panel.

Each fire alarm zone has two lights, one yellow, which lights up in the event of a fault, and the other, red, which lights up when there is a fire.

Testing The Circuit of The Fire Alarm Panel:

Short circuit the output terminals of the siren and keep it in the same position, the Sounder Fault light will turn on and the buzzer will sound. Press the Silence Fault button, as a result, the buzzer will turn off, but the Sounder Fault light will remain on. Remove the short circuit so that the device returns to normal mode.

Repeat this test by opening the siren circuit from the terminals.

To test the circuit of the detectors, we must test the three states of open circuit, short circuit and fire state.

For the first two cases, we open the circuit or short circuit, and as a result, the Fault light corresponding to the same zone is lit.

To test the fire condition, we connect the two terminals related to the zone with a 470 Ohm resistor, the connection is created, which causes the control current to increase, and as a result, the panel goes into the fire condition and the red light of the same zone lights up.

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