Can someone explain. To me how fire alarm systems work? How are they powered everything
In: Engineering
You have different sensors for heat and smoke, which are connected to a central unit.
If a detector sees some signs for a fire, this will be send to the central unit which decide if it is a fire and what to do.
Most likely an alarm horn and light will go on, maybe the fire department will be automatically called.
Often you have also stuff like disabling elevators (after driving them in the lowest floor), closing fire protection doors, shutting off flammable gases and electrical applicances.
What exactly do you want explained? How they work? Everything is wired to a central processor (the actual alarms, fire call points, smoke & heat detectors, sprinkler systems, other extinguishing agents or systems etc). If the smoke and/or heat detectors are tripped or if someone activates a call point, the alarm sounds.
They are powered by the mains just like everything else in the building, usually with a standby battery that is also charged from the mains so that in the event of a power outage, the alarm systems can still function.
The first fire alarms had a pair of contacts separated by a layer of wax. In a fire the heat melted the wax and a circuit was made that rang a bell. Modern systems aren’t much different, but use more sophisticated methods.
Detectors are alerted by high temperatures or smoke. Once they are activated they set alarms off and shut down the HVAC systems and if necessary evacuate smoke from egress points. This is all hard wired relay logic aka switches
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