FA Zones/Loop

Could someone be kind enough to explain the difference between FA Zones and loops?

Also what determines how many zones you need and what determines how many loops you need?

Thank You

A zone is a circuit on a conventional panel. Devices (pulls, smokes, etc.) are wired in parallel, with a resistor at the end of the line. Electrical current is passed through, and if a short is detected, the panel goes into alarm. If an open circuit is detected, that’s a trouble.

A loop (SLC) is the addressable equivalent. Instead of just electricity, the circuit transmits data, and an EOL resistor isn’t needed because the devices can “talk” to the panel.

Here’s a great page explaining the difference:
http://www.douglaskrantz.com/BlogLoopSupervision.html

I will expand on this. A zone in addition to having an electrical definition can have a physical definition. As the drawing below shows, a building segmented into protected areas divided by fire/smoke barrier walls also are zones. In a conventional hardwired system the electrical zones would be confined to the physical area zones. Sometimes an area contains several electrical zones, also known as an Initiating Device Circuit (IDC), each connected to specific device type. There could be a manual pull station zone, a smoke detector zone, and a sprinkler flow zone, etc. Each of those electrical zones constitute a IDC loop as described in the previous post.

[attachment=0]fire_alarm_zone.png[/attachment]

A loop is an electrical circuit which can be an IDC, a Notification Appliance Circuit (NAC), or a Signaling Line Circuit (SLC). A hardwired IDC or NAC is electrically supervised usually using an End Of Line Resistor (EOLR) which allows the panel to constantly check the integrity of the wiring. An SLC uses digital polling to the connected devices which report their condition by answering the poll. If a wiring fault occurs the device cannot answer the poll so the panel creates a trouble condition for that device.

The number of zones needed is determined by the building codes, fire codes, the square footage of the building, and if it is one floor or multiple floors. I will not begin to detail the various codes here.

The number of loops needed depends on the type of system. In a hardwired system at least one IDC is needed for each physical area zone. The devices connected to the hardwired IDCs can be wired to control Air Handling Units (AHU), dampers, and other functions. These functions can also be controlled by relay contacts in the panel. An addressable system can operate 200 or more devices per SLC loop. This means an SLC loop can operate Initiating Devices in several physical area zones. Control of AHU and dampers is then controlled using fire alarm control panel software programming rather than hardwired controls. An addressable system needs as many SLC loops as it takes to operate the required number of devices designed by the electrical or fire protection engineer.

are there typically two separate loops for the notification devices and the initiation devices or can they both be in the same loop?

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are there typically two separate loops for the notification devices and the initiation devices or can they both be in the same loop?

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IDCs and NACs are separate loops. Even on Simplex panels using addressable notification appliances the IDNet loop operates the initiating devices and auxiliary relays only. The IDNACs are separate addressable loops only for the notification appliances.