Fire Alarm Wiring Types
By: Bernie Cooperson, CET III, Technical Support Manager

We need to continue with the correct wire for installing a fire alarm system that is intended for where and how the wire will be installed.  Today, almost all new fire alarm systems are power-limited.  The National Electrical Code Article 760 is the reference that covers the installation of wiring and equipment of fire alarm systems, which includes all circuits controlled and powered by the fire alarm system.  This Code, among others, is a good reference to have in your overall technical library.  The wiring systems relating to Fire Alarms are described in the NEC as “the portion of the wiring system between the load side of the over current devices or the power-limited supply and the connected equipment of all circuits powered and controlled by the fire alarm system.”

Power limiting is accomplished by the fire alarm equipment manufacturer.  The manufacturer does this by limiting the amount of electrical energy available to a level that is incapable of electrocution or igniting structure fires in ordinary installations. When a testing laboratory (such as UL®) evaluates and verifies that the power available on a fire alarm control panel terminal is totally limited in accordance with NFPA 70-2002 Chapter 9 Tables 12A and 12B, then the alarm equipment is listed and labeled as being power-limited -- that is -- inherently safe.

The most common wiring method used on power-limited systems includes using a specific type of power-limited cable.  There are three types, marked “FPL” (Fire Power Limited, general purpose), “FPLR” (Fire Power Limited, Riser), and “FPLP” (Fire Power Limited, Plenum areas). The “FPL” type is referred to as a “horizontal” cable, as it can only be run parallel on a floor and cannot go upwards or downwards between floors.  The “FPLR” type of cable can be run the same as the FPL type with the addition of the ability to be run vertically between floors or often referred to a riser.  The FPLR cable can penetrate between floors, but this penetration requires proper fire stopping.  (Fire Stopping is another totally separate subject that the installer is required to be taking in to consideration when running cables as well.) The FPLP cable is able to be run in the two preceding manners plus in an area which is being used for HVAC environmental air, or plenum. If it is economical, if an installer stocks only plenum rated cable, it can be run almost anywhere and be Code compliant.

Most people overlook that this is but one of three wiring methods permitted by NFPA 70 to be used on power-limited fire alarm systems.
The three permitted power-limited wiring methods are:

1. Use power-limited cable marked “FPL”, “FPLR”, or “FPLP” with an overall insulation of 300V and conductor size as small as 26 AWG.  Typically, the smallest gauge of wire run for most fire alarm is 18 AWG.

2. Use National Electrical Code NFPA 70, Chapters 1-3.  For example, this would require THHN conductors installed in EMT (conduit) indoors and THWN conductors installed in ENT (PVC) outdoors. Conductors insulated to 600V and conductor size as small as 14AWG, (18AWG and 16AWG are permitted, with restrictions).  Refer to NFPA 70-2002 760.52 Wiring Methods and Materials on Load Side of the PLFA Power Source.

3. Use non-power-limited cable marked “NPLF” (general purpose), “NPLFR” (Riser), or “NPFLP” (Plenum), with an overall insulation of 600V and conductor size as small as 18AWG.

Additional references to other NEC Code articles include:

• Article 110.3(B) allows a maximum 4.4V volt-drop versus the 0.6V volt-drop found in Chapter 2.
• Article 300.15 requires a box for all fire alarm splices and terminations, unless an integral box is provided as part of the device. Very important: This article also requires a bushing to protect cables as they enter and exit boxes and raceway.
• Article 300.22(C) restricts the type of wire used within “other spaces used for environmental air”, which is commonly referred to as a plenum ceiling. The wiring material shall be low smoke producing such as cables marked “NPLFP” or “FPLP” or to enclose cables and conductors in the space within metal raceway.   This includes the cable ties being used to support or bundle wires are required to be plenum rated as well.
• Article 310.11(A) requires securely fastening cables and conductors to the building structure, and not to use the suspended (dropped) ceiling as support. There are many choices available from electrical distributors to the installer to properly support the fire alarm wiring independently and possibly save labor in the process.
• Article 760.10 which covers Fire Alarm Circuit Identification.  Fire alarm circuits shall be identified at terminal and junction locations in a manner that will prevent unintentional interference with the signaling circuit during testing and servicing."

Zoning
By George Boyett, VES Technical Support

Zones allow the contractor to group the fire alarm devices at the location. A zone is typically defined as all the devices found in a particular area of the site (first floor, apartment suites, conference room, lobby, etc.), but a zone can also be used to group devices of a particular function (Blower shutdown, power shunts, displays, pull stations, etc).  

Zoning has several practical benefits when it comes to fire alarm panel operations. The most common benefit is partial activation of the panel during an alarm, in which only the general alarm outputs (NACs, relays, lamps, etc) that trigger are the ones assigned to the same zone as the input that is in alarm.  

An example of zoning a location maybe a building with two wings and central hall, each section’s inputs and outputs can be assigned a zone. When an input device of a section activates then the only output devices of the same zone will trigger.

With FACP networking zones can include devices from several fire panels.  This feature gives the contractor more flexibility where the project requires installation of multiple panels. 

To use the previous example each section could have a fire panel that is part of a network.  Each section’s panel has its own zone.  However several input and output devices on the central panel were assigned to the zones of the two wings.  These devices will work in the zone as if they were on the same panel.

Zoning also helps in creating Cause and Effect Relationships. In large installations a contractor can easily face using dozens, if not hundreds, of input and output devices that require relations that can number in dozens.  Instead of selecting each device over and over again, the contractor just assigns all the devices to zones and then selects the zones he wishes to use in a Cause and Effect.  So when any input in a zone activates, all the assigned outputs of a zone, designated as an effect, will trigger.  On the VES line of Fire Alarm Control Panels Cause and Effect Relationships can use zones, individual devices, and subpoints together.

To take the example further, the location requires a way to disable a section.  The contractor could set up an input device with a key switch.  He creates a Cause and Effect where the key switch will disable a zone.  (This example is an easy task with a VES panel and a programming utility like eSP Discovery and Loop Explorer).

As was previously mentioned, zoning effects the triggering of general alarm outputs.  On the VES Fire Alarm Control Panels when an output device (NAC, relays, display channels, etc.) is set for general alarm any input in the same zone will trigger the device. The contractor does have the option to set an output to only trigger by a cause and effect, an unmarked device flag in eSP Discovery or Loop Explorer.   A non-general alarm output can be assigned in a zone with general alarm outputs, but it will only trigger by a cause and effect.

With all the options and possibilities of zoning a contractor can easily need dozens or hundreds of zones to properly configure a fire alarm system.  The VES fire alarm control panels have 500 zones available.  With 500 zones, a contractor should have enough to organize the fire alarm system as they see fit.