Common Wire in a Fire Alarm System

Typical Wiring Systems

• A typical fire alarm or smoke detector will be set up on either a two- or a four-wire system, according to System Sensor. The primary difference between the two types of wiring systems is in from where they derive their power. The two-wire system gets its power from the initiating control circuit of the fire alarm control panel. A four-wire system, on the other hand, will be powered by a separate pair of wires that connect directly to another power source. In other words, they bypass the fire alarm control panel and are powered by a secondary source, rather than the system itself.

Limits

• The size of the wire used, along with the distance that the wiring system will transmit signals, is determined by the manufacturer of the alarm itself. In other words, the manufacturer determines the quality of the alarm based on its manufacturing specifications. Edwards Signals notes that the manufacturer, by virtue of the way that it creates its product, may prohibit the installation of multiple circuits on the same conduit. The actual installation requirements, however, are determined by local, state and national wiring codes.

Wiring Configurations

• Wiring configurations in fire alarm systems fall into one of two primary categories. Initiating device circuits are the wiring configurations that determine how the system components are connected to the fire alarm control panel. These components include the smoke detectors and manual pull stations, for example, that initiate the fire alarm-sounding sequence. On the other hand, the indicating circuits are those that read the signal from the control panel and warn the occupants of the impending fire hazard in the form of bells, horns, strobe lights and other visual and audio warnings.

Wireless Circuits

• Wireless circuits are also common among fire alarm smoke detectors. These circuits are those that are often installed by the homeowner. The power source is usually a removable battery, rather than an external source connected by a wired circuit. These are set up in such a way that the alarm will sound when the battery's power has depleted to a level at which the alarm will no longer properly function, due to power loss.