Case study: Complex fire alarm system
Standard high-rise buildings represent moderately complex systems because of the number of monitoring points and outputs. However, as high-rise buildings become interconnected with common podiums, systems become even more complex.
Multiple megaresorts in Las Vegas and Cotai, Macau, include multitower, high-rise/casino complexes that require life safety systems integration via fire alarm systems. Each megaresort may include theaters, shopping centers, live performances, multiple restaurants, nightclubs, and other facilities to attract guests. The many devices and appliances installed throughout these buildings to achieve compliance with local codes and standards require multiple networked fire alarm panels to communicate with one another.
Modern fire alarm control units (FACUs) allow up to 3,180 total devices to be monitored by one panel. For example, a panel from one manufacturer allows 159 detectors and 159 modules per signaling-line circuit (SLC) and the panel has capacity for up to 10 SLC cards. Each panel also must have other “cards,” or plug-in devices to accommodate either notification appliances or networking. For a large resort containing multiple high-rise towers and a podium, 10 SLC cards is not enough capacity for SLC devices, especially noting that a limited number of smoke detectors may be connected to each SLC card loop. Therefore, fire alarm panels must be networked together.
Smoke detectors are required in guest rooms, corridors, and various other areas throughout the resort. Historically, hotel guest rooms were permitted to be outfitted with single-station, 120-V smoke alarms with battery backup that were not monitored by the fire alarm system. Some authorities having jurisdiction now require guest rooms to have monitored smoke detectors with sounder bases in guestrooms.
Even building owners/operators are mandating system-monitored smoke detectors so that the property is aware if a smoke detector has been tampered with or needs to be cleaned/maintained. This increases the number of points on a fire alarm system. Multiple fire alarm panels are necessary to monitor each of the devices and then provide an appropriate output based on the sequence of operation.
Each fire alarm system manufacturer has their own set of hardware and software that needs to be used to connect multiple FACUs and allow them to communicate with each other. Typically, the FACUs will all connect to a main FACU in the fire command center for the property, where staff will monitor the system for any troubles, supervisory signals, or alarms. Multiple panels networked together use a Class X pathway configuration. Class X pathways provide a redundant wire path so that if a pathway is broken (single open) or short circuited along the path, communication is still available between panels.
In addition to smoke detectors, multitower high-rise buildings with common podiums often require smoke management, or at the very least pressurization of exit enclosures. In either case, the complexity increases because the fire alarm system is often the designated system to achieve the UUKL smoke-control panel designation required by building codes.
Thus, the fire alarm system also serves as the highest-priority signaling system for smoke-control fans and dampers, which might also be controlled by a building management system or building automation system. This requires not only additional points to monitor, such as fan status and damper status, but also output functions for when to start/stop fans, open/close doors and dampers, and other functions as may be necessary for the specific smoke-management design.