life safety systems
BY THOMAS P. HAMMERBERG
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
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 intend-
ed 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 in-
stallation, 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.
HAMMERBERG, SE T, CFPS, is president of Hammerberg & Associates Inc. He
serves as the Automatic Fire Alarm Association (AFAA) Inc.’s technical director.
Tom represents AFAA on a number of NFPA committees. He is also a member of
the ICC Industry Advisory Committee. He can be reached TomHammerberg@