Douglas Krantz - Technical Writer - Describing How It Works

Do I Assign Zones to NACs or NACs to Zones?

By Douglas Krantz | Life-Safety

Do I Assign Zones to NACs or NACs to Zones?


Do I Assign Zones to NACs or NACs to Zones?


Greetings Douglas,

Do I need to assign my Notification Appliance Circuits (NACs) to Zones, or assign the Zones to the NACs?

Thank You, CG

To understand where the wires for the Notification Appliance Circuits (NACs) should run, the word "Zone" needs to be understood.

Firefighting Zone

This is the part of the building (zone) that the firefighters look for when there's a fire. Usually, this part of the building is separated from the rest of the building (zone) using fire / smoke barrier walls, fire doors that close when there's fire or smoke, and HVAC fire / smoke dampers that close.

Inside this part of the building (zone), if a fire alarm input device goes into alarm, this is where the firefighters are sent.

Fire Evacuation Zone

When there's a fire, the occupants in this part of the building (zone) are told by the horns, strobes, speakers to evacuate.

Silk-Screened Zone Labels on the Fire Alarm Control Panel

These are labels on the control panel, or on the power supply designating the inputs or the outputs. However, the manufacture who silk-screens on the labels has no idea about the building, the fire fighting zones, or the evacuation zones.

The silk-screen labels inside the panel just labels, and are arbitrary. The labels may as well be Input 1, Input 2, Input 3, Etc., or Output 1, Output 2, Output 3, Etc.

Of course, when the silk-screened labels say something like Zone Input 1, Zone Input 2, Zone Input 3, Etc., or NAC Output 1, NAC Output 2, NAC Output 3, Etc., the manufacturer is giving more information about the circuitry inside the circuit board, and more information as to how the building's circuit is supposed to be used.

These are silk-screened labels; the labels don't show anything about the kind of building being protected.

Evacuation Type

To understand how the circuits need to be laid out, the first requirement involves the evacuation type. There are three major types if evacuation: Total Evacuation, Staged Evacuation, and Defend in Place.

Total Evacuation This is like a school. Everyone in the building is supposed to leave, immediately, when the fire alarm system sounds off.

Staged Evacuation This is like a high-rise building or a large sprawling building. Those in the zone (that has the fire), plus everyone in the adjacent zones (above, below, all zones next to it) are told to leave. In essence, everyone in the zone of incidence, and everyone in all adjacent zones is told to immediately evacuate.

Along with the evacuation, often a separate alert tone or alert message is sent to all of the others in the building. Having the alert message can be very helpful to the occupants, or the alert message can be very confusing to the occupants. Whether or not there should be an alert tone or message is something that needs to be discussed with the fire marshal, and the building owners.

The staging, or partial evacuation, is mostly there because the escape routes are small. Stairways in high rises, for instance, are very small and can be easily blocked by too many people leaving all at once. When using staged evacuation, for safety, anyone in immediate danger can escape first, then after that, those who are not in immediate danger can get out.

Defend in Place This is for situations where the occupants can't get out of the building. The fire alarm system acts like a total evacuation or a staged evacuation system, but the occupants actually get behind a closed door, and wait.

Extra Considerations

In residential buildings, or institutional buildings, where there are minihorns, speakers, or sounder bases inside the residential areas, these minihorns or sounder bases should be on separate NAC circuits from the common areas, like hallways.

There are several reasons for this separation: one is a maintenance issue, another is redundancy.

Notification Appliance Circuit

Circuit: This is a pair of wires (circuit). One end of the pair of wires is connected to the control panel or other panel. Along the route, the pair of wires (circuit) is connected to the devices. The wires carry the needed power. Usually, connected at the far end of the wires (circuit) is an end of line resistor.

Appliance: This is the device (appliance) connected to the wires. A device could be a horn, a strobe, a speaker, etc. Sometimes, even though the devices are separate devices, the devices are combined inside a single box, like horn/strobes or speaker/strobes.

Notification: Letting people know about a fire is notifying them of the fire.

So that people will take action to protect themselves and others, a Notification Appliance Circuit, or NAC, is used to carry power to the horns, strobes, and speakers.

Assigning NACs to Zones or Zones to NACs

Firefighting zones and evacuation zones are an integral part of a building. Adding a fire alarm system doesn't change the zones, so the fire alarm system, including the notification circuits (NACs), has to match the building's zoning and evacuation needs. Just be aware of the different kinds of zones, and what is really needed for the NAC.

Also, talk to the various AHJs, including the fire marshal and the building owners to get their opinions. You may have to educate them on what kind of zoning you mean, but once educated, they may be able give better guidance.

Douglas Krantz

facpdoug@douglaskrantz.com
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