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
1. Applies to fire alarm systems and emergency communications systems (ECS)
2. Applies to notification appliance extender power supplies
3. Must have two independent means of power
4. Branch circuit for commercial power is to be dedicated
5. The disconnecting means must be Identified
6. Standby power must be at a minimum, 24 hours
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Dr. Shane Clary
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