Alarm contractors repeatedly test the fire alarm systems that they design and install in households across the country, including their duty to activate each of the system’s automatic initiating detection devices that they install throughout the protected premises, such as UL 268-listed smoke detectors.
When focusing on NFPA 72 compliance, it is important to recognize the design of how all household combination listed control units operate.
NFPA 72 Technical Analysis
As part of this technical analysis, our industry’s professional and technical community knows that hard-wired burglar alarm motion detectors and audio glass break detectors require continuous DC power.
Given that, all combination listed control units provide installation instructions and a schematic that identifies where an installer is required to connect this circuit in order to get auxiliary power to these burglar alarm field devices.
At the same time, the single data-bus circuit on these control units also requires continuous DC power to operate all the system’s data-bus connected devices. So, each device on the single data-bus circuit is required to connect in parallel with each other.
Precisely, and by design, the DC power that is required for aux power is also manufactured to connect in parallel with the data-bus circuit’s DC power outlet. So, in sum, “both outputs” are one and the same.
Likewise, this is perfectly aligned and identified where an installer is required to connect the system wiring as documented on the schematic for the combination listed control unit.
If fire attacks any portion of the single data-bus circuit wiring and/or any of the data-connected devices on a combination listed control unit, the introduction of a single short circuit fault condition will instantly and simultaneously shut down the aux power output of the control unit; the same holds true if the short circuit fault condition is introduced onto aux power.
Fundamentally, this also includes all data-bus connected devices and everything that rides in parallel with the single data-bus circuit.
As a result of this equipment manufacturer’s design configuration, the combination listed control unit is instantly rendered non-functional. Therefore, in this scenario, the burglar alarm portion of the system takes down the fire alarm system.
Simplified and Overtly Dangerous
Simplified and overtly dangerous, these deficiencies violate the mandatory minimum requirements of NFPA 72 because compliance cannot be achieved, in spite of an alarm contractor complying with the equipment manufacturers installation instructions and NFPA 72 standards.
The criticality of life safety and the foreseeable consequences are to occupants in the home if they are not given early warning during a fire emergency.
Alarm contractors are required to comply with the equipment manufacturer specifications of any control unit that they install, so there are no options. And to the extent that the installer wired the system differently, it would not function.
So, the only way to connect a hardwired, wireless or hybrid fire alarm system to a combination listed control unit cannot and does not comply with NFPA 72, the National Fire Alarm and Signaling Code.
Moreover, and continuing with this analysis, data-bus connected devices include but are not limited to remote system keypads, data-bus connected wireless radio alarm transmitters, zone expansion modules, auxiliary power supplies, wireless receivers/transceivers, input/output modules and any other devices that require continuous DC power, such as dialer capture radios.
Strictly speaking, let’s look at NFPA 72 with regards to what crystallizes part of its fundamental requirements. NFPA 72 states the following in pertinent part and incorporates the word “shall,” which indicates that the requirement is not recommended but, rather, is mandatory.
“Faults in other systems or components shall not affect the operation of the fire alarm system.”
As demonstrated time and again in NFPA 72, a fault is strictly prohibited from negatively affecting the operation of the fire alarm system. Yet, in spite of NFPA 72’s longstanding mandatory minimum faults mandate, combination listed control units shut down when a short circuit fault condition is introduced onto the system, as indicated above.
The Other End of the Spectrum
On the other end of the technical spectrum, this predictable failure and danger is not an option that an installer can change by wiring the control unit differently. Making changes to the combination listed control unit’s inherent functional parameters results in a fire alarm system that will not work and violates the listing of the product.
Nonetheless, besides the control unit failure, the short circuit fault condition also renders remote supervising station monitoring non-functional because, without DC power, no signals can be transmitted to the central station so that the fire department would be notified of the fire emergency.
By way of example, dialer capture radios are required to connect to the aux power of the control unit for DC power. So, once a short circuit fault condition is introduced onto either aux DC power or the single data-bus circuit, it becomes technically impossible for any radio to operate.
At the end of the day, alarm contractors state that their fire alarm systems comply with NFPA 72 because they are bound to comply with this fire code and statutory duty. However, with the deficiencies noted above, this is technically impossible to achieve when providing these services to consumers.
In closing, when it comes to life safety, compliance with NFPA 72 is mandatory because science has proven that it helps to save lives and it has avoided and/or minimized serious personal injury and/or death by providing an early warning to occupants in the home so that they can escape before the premises become untenable.
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