The Night the Lights Went Out in Berkeley
Most people take power for granted without realizing how many daily activities rely on it – until failure occurs. Nowhere is this truer than for fire/life-safety systems. A recent experience serves as a launch point to keeping systems up regardless of power challenges.
In prior editions of 72, there was a requirement for either 24 hours of standby for central station service, local or proprietary systems; or a requirement for 60 hours for remote station or auxiliary systems. This was changed several cycles ago, to the requirement that all systems be able to operate under the quiescent load for a minimum of 24 hours, and then be capable of operating all of the notification appliances for five minutes, or 15 minutes for a voice system. Mass notification or ECS systems are also required to be able to operate for the 15-minute timeframe.
The key word within in Paragraph 10.6.7.2 is, “minimum.” Depending on the type of system or the location of the system, there may be consideration to having the standby capacity extended. This may be through a risk analysis of the system designer, a decision by the owner or by direction of the authority having jurisdiction (AHJ).
At a minimum, the fire alarm systems at UC Berkeley would be able to operate for at least 24 hours, and then still have the ability to activate all of the notification appliances. Depending on the size of the batteries in use, and the standby load of the system, this time may be extended. I will discuss this a little more shortly.
The primary and secondary power requirements in place for a FACU or ECS control are the same for any remotely located control equipment, as found in Section 10.6.8.
Storage Batteries are found in Section 10.6.10. The batteries shall be marked with the month and date of manufacture. The batteries shall also be recharged after a discharge within 48 hours as required by Paragraph 10.6.10.3.2.
Testing and Calculation Procedures
There is a trend among AHJs to go to a protected premise as part of an acceptance test and remove the primary power 24 hours prior to the full test. Then, 24 hours later, they run all of the notification appliances on the standby batteries. While this does demonstrate that the batteries were sized correctly, it also depletes them.
NFPA 72 requires that the batteries may then have up to 48 hours to recharge. If there were to be an actual power failure within a day of the test, the batteries may not be back to full capacity and fail prior to the required 24 hours. If there were to be an actual fire, there may not be enough capacity to sound the notification appliances. As demonstrated at UC Berkeley, power failures do occur.
In the words of Bob Newhart, “Stop it.” The standby battery calculations are intended to provide proof that the system will have the proper secondary power requirements. If the fear is that the batteries may be bad, then use a battery load tester during the final inspection. A number of these may be purchased through several vendors. I equate this to the hydraulic calculations required on a fire sprinkler system. I have yet to see an AHJ require sprinklers in the most remote location of the system be fused to verify the hydraulic calculations were correct.
Understand the requirements of Section 10.6 and you should not experience any issues with either the primary or secondary power for the systems you design and install.
6 Basic Power Supply Requirements
- Applies to fire alarm systems and emergency communications systems (ECS)
- Applies to notification appliance extender power supplies
- Must have two independent means of power
- Branch circuit for commercial power is to be dedicated
- The disconnecting means must be Identified
- Standby power must be at a minimum, 24 hours
You might also want to read:
- Will Your Generator Hold Up During an Emergency?
- HEOA Update: Fire Incident Reporting Requirements
- Most Common Fire Alarm System Problems
- Video Expands Limits of Fire Detection
- Video Can Prove Valuable in Fire Applications
- Fire Incident Reporting Requirements
Shane Clary, Ph.D., has more than 37 years of security and fire alarm industry experience. He serves on a number of NFPA technical committees, and is vice president of Codes and Standards Compliance for Pancheco, Calif.-based Bay Alarm Co.
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