Douglas Krantz - Technical Writer - Describing How It Works

If a Building has 3 Fire Zones, Do I need 3 NAC Zones?

By Douglas Krantz | Life-Safety

If a Building has 3 Fire Zones, Do I need 3 NAC Zones?


If a Building has 3 Fire Zones, Do I need 3 NAC Zones?


Greetings Douglas,

If a building has one floor with 3 Fire zones, and a separation using a 1-hour firewall between zones, should the building have 3 audible horn NAC circuits [Notification Appliance Circuits]?

Thank You, KW

To answer the question, the word Zone has to be defined.

Zone

All buildings have three types of zones:
  • Firefighter Zone
  • Evacuation Zone
  • NAC Wiring Zone

Firefighter Zone

This is the area of a building the fire department goes to find the fire. The area will be separated by firewalls from other areas of the same floor it's on, and by the ceiling and floor from the floor above and the floor below.

Usually, its actual size is restricted to allow the firefighters to work in a limited area.

Evacuation Zone

When there's a fire, this is the area of a building that sounds off with horns and strobes. Sometimes the evacuation zone is the same as the firefighter's zone, sometimes the evacuation zone covers a dozen or more firefighter zones.

Example: A large school may have over two dozen firefighter zones covering several floors, and even have some out-buildings. When there's a fire, though, the school is really just one evacuation zone, which includes the out-buildings.

Example: A small apartment building that has three floors and a basement might have four firefighter zones. Usually, though, it still has only one evacuation zone.

Example: A tall high rise office building standing 27 floors high, and having three basement floors underneath, will have 30 evacuation zones. Each floor is a firefighter zone, and each floor is also an evacuation zone.

When there's a single Evacuation Zone, the whole building is evacuated at once; when there's multiple Evacuation Zones, the Evacuation Zone with the fire, and all adjacent zones (all sides, above, and below) are evacuated.

NAC Wiring Zone

The NAC Wiring Zone is the area of the building that has the wires for the NAC circuit (Notification Appliance Circuit), which carries the power to the Notification Appliances: the horns, strobes, chimes, speakers, etc.

Depending on what the AHJ wants, this NAC Wiring Zone can be limited to powering a single Firefighter Zone, or be allowed to provide power to the Notification Appliances in several Firefighting Zones.

On the fire alarm control panel, using a silkscreened label next the screw terminals, the label shows where the wires for the NAC Wiring Zone are attached. When the panel is being manufactured, though, the manufacturer has no idea how the panel is going to be used, so the silkscreened label doesn't mean anything about the building zones.

AHJ or Authority Having Jurisdiction

According to the NFPA 72, the AHJ can be the fire marshal or other government building official, the insurance agent for the building owner, and even a representative of the building owner (like the architect or engineer). If there's a question, talk to the AHJ. The AHJ may have some requirements.

Long Term Plans

For the question, one possibility is that this three-Firefighting Zone building, the zones being separated by fire walls, is going to be a rental building. Each of the three zones are going to be rented out to a different entity. Over the life of the building, each of the Firefighting Zones may be remodeled at different times.

If that's the case, it may be a good idea to use a different NAC Wiring Zone for each of the three Firefighting Zones. This keeps the NAC zones isolated from each other.

For instance, by using different NAC Wiring Zones for each Fire Fighting Zone, when the middle zone is being remodeled, the remodeling won't affect the fire protection on either of the end zones.

Zones

Remember, depending on what the word is being used for, the word "zone" may be:
  • Firefighter Zone
  • Evacuation Zone
  • NAC Wiring Zone




Douglas Krantz

facpdoug@douglaskrantz.com
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