Tall buildings require different systems than “standard” buildings. This is true for fire alarm systems as well as electrical systems. So what defines a “tall” building? The International Building Code (IBC 2000) and the Building Construction and Safety Code, NFPA 5000TM-2002, define high-rise buildings as buildings 75 feet or greater in height measured from the lowest level of fire department vehicle access to the floor of the highest occupiable story.
Once a building meets a code definition for a high-rise building, the fire alarm requirements ratchet up a few notches. The National Fire Alarm Code, NFPA 72-2002, defines a high-rise fire alarm system as an emergency voice/alarm communications system. Such a system provides dedicated manual and automatic facilities for the origination, control and transmission of information and instructions pertaining to a fire alarm emergency to the occupants of the building, including fire department personnel.
Emergency voice/alarm communications systems most often provide notification for partial evacuation or relocation of the occupants of a high-rise building. They also provide automatic or manual voice capability to permit voice instructions to the building occupants, either selectively or throughout the building.
Most electrical contractors have already found out the hard way that emergency voice/alarm communications systems offer more complications than typical low-rise fire alarm systems. Reasons include:
1. Other systems and devices must interface with the fire alarm system: stairwell pressurization; HVAC damper control; smoke control; door control; and security systems.
2. Risers for the notification appliance circuits must survive during a fire.
3. The sequence of occupant notification must meet the requirements of both local and state codes.
4. The system must assure intelligibility of the voice messages.
5. The system must incorporate firefighter telephones, fire department radio repeater systems and/or bi-directional amplifiers.
All these requirements add to the normal installation issues encountered in any high-rise installation. Contractors with high-rise building systems installation experience know that the fire alarm system must be planned, installed and programmed well in advance of the scheduled building opening date. This procedure allows for a complete pre-acceptance test and re-programming, if necessary, of the emergency voice/alarm communications system before calling for the fire department acceptance test.
Any contractor, prior to bidding such an installation, must ensure that the estimator and bidder for the fire alarm system equipment understand the requirements for the system operation and the programming of the system to ensure that operational sequence. If the contractor does not plan the wiring of each system interface properly, no amount of programming will rectify that mistake.
The design and installation of survivable fire alarm systems must ensure that attack by fire within an evacuation signaling zone (generally a floor) will not impair control and operation of the notification appliances outside the evacuation signaling zone. This means that a fire on one floor will not cause a fuse to blow or short out circuits that affect the operation of the speakers and strobes on any other floor, even when the risers for those circuits pass through the fire floor.
The documentation submitted to the Authority Having Jurisdiction (AHJ) must describe such performance features provided by the contractor to assure survivability. This will ensure the AHJ approves the method intended for use to comply with the survivability requirement.
The Code requires that all circuits necessary for the operation of the notification appliances be protected until they enter the evacuation signaling zone that they serve. Any of the following methods meet the survivability requirements:
1. A two-hour rated cable or cable system
2. A two-hour rated enclosure
3. Performance alternatives approved by the Authority Having Jurisdiction.
Interconnecting wiring to the fire command center control equipment located remotely from the central control equipment must use survivable installation methods for riser circuits to resist attack from a fire.
A contractor can easily avoid problems by teaming with a knowledgeable and responsive emergency voice/alarm communications systems supplier. If your usual supplier has never supplied an emergency voice/alarm communications system, you do not want your project to be his/her “trial” installation. This represents one of those instances where accepting a low bid without investigating the suppliers’ qualifications may generate the most heartburn.
High-rise buildings and emergency voice/alarm communications systems for such buildings present a challenge. Make sure you can meet that challenge by being thoroughly aware of all special Code requirements by understanding the design, understanding the importance of coordination with the other tradespeople early in the installation process and ensuring the use of a qualified emergency voice/alarm communications systems supplier. EC
MOORE, a licensed fire protection engineer, frequent speaker and an expert in the life safety field, is a co-editor of the current National Fire Alarm Code Handbook. Moore is a principal with Hughes Associates Inc. at the Warwick, R.I., office.