The benefits and challenges of wireless fire alarm systems

Although designers should consider wireless fire alarm systems for their portability, easy installation, and flexibility, they must also consider cost-effectiveness for each application.

07/12/2017


Learning objectives:This article is peer-reviewed.

  • Explore the fundamentals of wireless fire alarm technology. 
  • Understand how to use wireless fire alarm technology and its advantages for nonresidential applications. 
  • Realize the benefits of fire alarm technology and its current developments. 

When provisions for wireless alarms were in their infancy, most authorities would not permit their installation due to reliability concerns and the fact that manufacturers had not actively sought development. Architects and interior designers complained that if they, or the owner, did not like the location of a fire alarm device or appliance, it would require multiple trades to relocate the device or appliance, even if it was just a foot or two away from the original location. An electrician would have to come out to relocate the conduit, backbox, and wiring, and the fire alarm technician would have to reinstall the device or appliance. In many cases, other trades would also have to get involved, like drywall, framing, etc. 

While the advent of 3-D modeling allows design teams to coordinate equipment locations more accurately, owners and designers still may not get the “feel” for a space until it is built. Mock-ups are often used, but it is not cost-effective to mock-up an entire building. Fortunately, for those designers dealing with last-minute locations for fire alarm devices, wireless technology has come a long way in the past 20 years, and the future looks bright.  

Figure 1: This is a photo of multiple condensing units on the roof of an older colocation facility. The power usage of these condensing units would count toward the heat-rejection peak fan-power portion of the mechanical load component. Defining wireless fire alarm technology 

In its present state, wireless technology is not the be-all and end-all that allows designers to put devices and appliances wherever they want. The spacing criteria of NFPA 72: National Fire Alarm and Signaling Code still applies. Designers must meet the minimum standards set by NFPA 72 for locating equipment on walls and ceilings. The locations of devices and appliances must meet the performance objectives for either detecting fires or notifying occupants, as applicable. Most important, wireless does not mean that there will not be any wires. Just like your Wi-Fi connection at home, there will be transmitters and receivers that must be wired and powered.  

Residential detection and notification are specifically known in NFPA 72 as single- or multiple-station smoke alarms. Smoke alarms that are installed in new homes are generally required to be connected to 120 V ac power along with a battery backup. New installations also require the alarms to actuate in multiple rooms if smoke is detected in only one room. That technology is wired or wireless depending on the type of system installed.  

Ultimately, though, what designers and owners have been yearning for is wireless fire alarm systems for commercial applications.  

Wireless fire alarm technology is referred to in NFPA 72 as low-powered radio (wireless) systems. That specifically refers to the use of wireless signal transmission via radio wave signals. The frequencies and modulation types are all regulated by the Federal Communications Commission (FCC), but the low-power frequencies for fire alarm systems are typically outside of thresholds requiring licenses. 

The term low-powered radio also indicates that signals are not able to be transmitted over appreciable distances. Manufacturers of wireless fire alarm systems will clearly indicate the maximum distance between transmitting and receiving devices. Some manufacturers have developed technology that uses fire alarm devices as both a transmitter and a receiver to create a mesh that allows the network to communicate in multiple directions rather than just bi-directionally. However, the distance limitations still apply, and often the groups of transmitter/receivers must still be within range of a repeater or a primary network panel.  

Historically, authorities have been wary of wireless fire alarm systems, primarily because of their reliability. These days, however, even in-building firefighter two-way communication systems are being prescribed by building and fire codes requiring two-way radio communication systems and eliminating the traditional firefighter phone jacks in buildings. Two-way radio communication systems are being enhanced within buildings with the similar type of repeater technology used in wireless fire alarm systems. Both technologies also follow similar principals for distributed antennae systems (DAS) that are provided in buildings to enhance mobile telephone signals.  

Implementing wireless fire alarm technology 

Similar to what is required by the International Fire Code for two-way radio communications, designers and installers of the available wireless fire alarm systems must determine if the site and building are suited for wireless technology by conducting a radio frequency (RF) survey. For emergency two-way radios, heat maps often can be used by identifying the emergency broadcast frequency-signal strength at various locations and identifying when the signal falls below acceptable levels. In-building repeaters or DAS would be used to boost the primary signal. For wireless fire alarm systems, the approach may vary but generally requires that actual wireless fire alarm transmitters and receivers be onsite with equipment to evaluate their signal strength throughout areas of the building or property where they will be installed.  

There are instances where the use of wireless fire alarm systems may not be effective. As with most radio frequency transmission, building materials or other environmental aspects may impact the ability to install wireless fire alarms. In some cases, concrete construction may limit signal strength and even metal buildings may interfere with signals. Cores of taller buildings, like concrete/masonry elevator cores or stair cores, may reduce signals due to their construction. Prior to installing, the designer and installer should conduct a thorough RF survey with their equipment. If the building is new construction, designers should evaluate construction materials with the design team and still conduct an RF survey after construction. For new buildings, there should be mitigation measures in place in the event that the RF survey determines wireless fire alarm system communication may be questionable.  

Figure 2: A step-down transformer within a server room power distribution unit is shown. The inefficiency associated with the transformer would count toward the “ITE distribution segment” loss portion of electrical loss component.

Where are the best places for wireless fire alarm systems? While most manufacturers would like to answer with “everywhere,” they are also honest enough to state in their literature that not all facilities may be appropriate for wireless fire alarms. If you paired one of the greatest advantages of wireless fire alarms with one of their strongest detractors, existing construction or retrofits would be where wireless fire alarms are most advantageous. Since there are significantly fewer wired pathways, and RF surveys can be conducted at any time, existing buildings are key markets for wireless fire alarm systems.  

Casa de Shenandoah: Renovating a private residence into a museum 

While Las Vegas is known for its bright lights and pizzazz, there are actually sites that locals and tourists agree are historical. Mr. Las Vegas himself, Wayne Newton, formerly owned Casa de Shenandoah, a 52-acre property with eight homes. The property now serves as an attraction with the main house, a 9,000-sq-ft mansion, serving as a museum showcasing his lavish lifestyle.  

Unfortunately, changing a private residence to a museum does not happen overnight. To make the private residence accessible to the public, negotiations with authorities required that fire alarm detection devices be installed throughout the mansion with notification appliances along the publicly accessible path of the museum tour. The most effective means to make this happen was to provide a wireless fire alarm system.  

The benefits of a wireless fire alarm system were immediately apparent. Wireless smoke detectors could be installed throughout the building without impacting historical finishes. While the fire alarm panels and repeaters required wiring for power, they could be strategically located to limit the impact to aesthetic finishes. Since not all parts of the mansion were open to the public, the fire alarm panel and repeaters could be placed such that they could easily transmit and receive yet were not in plain sight of the public.  

However, one aspect became clear: A wireless fire alarm is not truly wireless. The notification appliances required wiring both for monitoring and power. Fortunately, the installation of notification appliances was limited to areas that were directly accessible to the public. In this case, it was possible to group appliances in strategic locations near repeaters and panels to limit the impacts to the building.  

Today, thousands of visitors visit Casa de Shenandoah each year to marvel at the lifestyle Mr. Las Vegas was able to accrue. For the owners and authorities, they know the public is afforded more safety than the previously private residence allowed. 

The case study demonstrates that wireless fire alarms are not truly wireless because of the panels and notification appliances. However, with savvy designers and installers, those obstacles become simple workarounds. During the RF survey, and working with the owner and architect, the designers and installers of the Casa de Shenandoah project were able to identify locations for panels and repeaters while simultaneously identifying how they could install the notification appliances with minimal intrusion.  

As noted previously, even a home Wi-Fi system is going to require some wires for power and a connection to the internet; so it is with wireless fire alarms. The additional challenge is that most required notification appliances are not wireless. At least one manufacturer has developed a low-frequency sounder for audible notification, but speakers and visual notification appliances (strobes) may require years more of development. To the developers of the low-frequency sounder’s credit, they tapped one of the most popular markets for wireless fire alarms: residential hotels, motels, and dormitories, since NFPA 72 requires low-frequency audible alarms in sleeping areas.  

The biggest issue associated with wireless notification appliances is the power consumption they require. Fire alarm system designers know from battery and voltage-drop calculations that the power-hungry notification appliance is the primary driver of battery size. In their quiescent state, notification appliances consume very little power. When the alarms sound and the strobes flash, the alarm appliances can and will drain batteries quickly.  


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