An Alternative Approach: Wireless fire alarms

In today’s world, wireless is our life. Your mobile phone and tablet operate on either a cell signal or Wi-Fi. We connect our computers using Wi-Fi most of the time, in our homes and offices and when we travel. Fire department personnel count on their radios for responding to alarms and communicating on the scene. 


Today, as communications methods for monitoring fire alarms move away from digital alarm communicator transmitters, the three most common methods of signal transmission to a monitoring facility are GSM cell coverage, Internet protocol communicators, and mesh radio systems. Two of the three are wireless technologies. As such, will wireless fire alarms and security systems be common in the future?


Wireless fire alarms have been around since the 1980s but have never really taken off. Some fire departments don’t allow them to be installed because of reliability concerns; however, the same fire departments trust their radios in emergency situations. Worries about interfering signals have slowed acceptance of wireless fire alarms, but is that really a consideration with today’s technology? Can wireless fire alarms be installed in all applications, or are they best used for special situations?


A number of manufacturers produce wireless fire alarm systems, and most, if not all, would agree they are not right for all applications. However, there are quite a few situations where this technology can solve problems where a wired fire alarm system would not be practical.


Wireless fire alarms must meet all of the same requirements as wired counterparts. They both must be listed per UL 864, Standard for Control Units and Accessories for Fire Alarm Systems. NFPA 72 has contained requirements for low-power radio (wireless) systems for many years. Technology has improved system quality.


Wireless fire alarm applications

Have you ever installed a fire alarm system in a building and found that you also need a fire alarm device in a remote building or location? Rather than running cable, it would be much cheaper to monitor that device wirelessly. NFPA 72 allows the use of combination systems, so in this case, you may use a wireless fire alarm panel connected to your wired building fire alarm system. 


I have seen pictures of a wireless system being used to receive a signal from a device located across a runway at an airport. If you didn’t use wireless, how would you get wiring to that location? Trenching would be prohibitively expensive.


Do you renovate existing hotels? NFPA 72 requires a low-frequency sounder for smoke alarms located in accessible sleeping rooms as well as for system notification appliances located in all areas where the signal is intended to wake sleeping occupants. In a matter of minutes, you can use wireless technology to upgrade the smoke alarms in sleeping rooms to produce a low-frequency sound. During installation, there is virtually no downtime for the hotel owner.


What about NFPA 72 requirements, such as monitoring for integrity? Wireless systems meet the same requirements as wired systems, but in a different way. Aren’t most installation problems related to wiring?


For example, if there is no wire, there can be no ground fault. What about an open-circuit fault? With a wired system, you must report a trouble condition within 200 seconds. You will just get a general trouble signal for an open on a nonaddressable system and one or more missing devices identified on an addressable system. If a wireless device, such as a smoke detector, is removed from its installed location, a trouble condition is reported, identifying the exact device that was removed. Control panels constantly monitor wireless devices. Each device that does not transmit directly to the panel must have at least two paths to transmit its signals to the control panel. If a repeater goes down, the device sends its signals using a second repeater.


Although there are no wireless audible and visible system notification appliances on the market, you can minimize wiring by connecting them to repeaters in the area rather than running the wire back to the control unit. The sounder bases used for smoke and carbon monoxide alarms provide sound wirelessly.


As I stated above, I do not think the time has come for all systems to be wireless, but there are enough challenging applications out there to at least consider adding wireless technology to your tool kit. I know of a number of electrical contractors who do this today to stay competitive in our diverse industry.

About the Author
Tom Hammerberg

Thomas P. Hammerberg

Life Safety Columnist

Thomas P. Hammerberg, SET, CFPS is an independent fire alarm presenter and consultant in The Villages, Fla. He can be reached at TomHammerberg@gmail.com.

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