Farenhyt_Family_2013Choosing the Correct Battery Size for your Fire Alarm System

Choosing the correct battery for your facility’s Fire Alarm System is certainly more difficult than choosing the battery for your TV remote control or stop watch. Moreover, the consequences of choosing the incorrect battery size for your facility’s Fire Alarm System could affect its ability to function properly and pass inspections. Thankfully, the National Fire Protection Association (NFPA) provides codes and standards that we can depend on for information and guidance on these Fire and Life Safety matters.

Fire Alarm professionals use NFPA 72 for the design, installation, and maintenance of Emergency Communication Systems and Fire Alarm panels. Written documentation by a certified Fire Alarm professional, which states that the system complies with NFPA 72, is required for any Fire Marshal to certify and approve the system. For this reason, it is extremely important to pay close attention to what the code tells us.

NFPA 72 states that the panel shall have a primary and secondary source of power. This makes power a particularly significant part of certification. For the most part, the primary power is 120 VAC and the secondary source is a sealed lead acid (SLA) rechargeable battery.

When determining what size batteries to use in a particular panel, one must take several factors into consideration: What type of system is it? What type of power supply does it have? What are the panel’s components and configurations? By adding the power requirements of each component in the Alarm System, one can compute what the appropriate battery size would be. Frequently, Fire Alarm Technicians utilize a battery calculation worksheet found in most power supply manuals to simplify the calculations. When the Technician enters the correct number of equipment on the worksheet, they are able to learn two important pieces of information:

      1. Standby Power Requirement (measured in amperes) – The amount of power required for the panel to operate under normal conditions. This is the main contributor to battery size. The main CPU board, the display screen, and any additional specialty boards/cards all require standby power.
      2. Alarm Power Requirement (measured in amperes) – The amount of power required for the panel to operate in “alarm condition.” The strobes, horns, emergency panel lights, and relays require alarm power.

“Once standby and alarm power have been calculated, they are multiplied by the time component given to the initial construction specification,” explains Sr. Engineer, Scott Kincaid, in his Brooks Equipment Hot Topics article, “Selecting the Correct Battery Size for Fire Alarm Systems.” He continues by explaining, “Standby times are usually 24 hours. This allows a full day to address the reason for the main power loss, which shows as a trouble condition on the fire alarm control panel (FACP). More stringent standby times call for 60 hours of backup. This amount of time allows the panel to operate without primary power through a normal weekend but results in larger batteries, more batteries, and more equipment to charge the batteries. If a technician calculated standby power to be 1.5 amperes, a 24-hour standby time would result in a minimum battery size of 36 Amp Hours (1.5 Amperes x 24 hours). That same standby power on a 60-hour standby system results in a minimum battery size of 90 Amp Hours (1.5 Amperes x 60 hours)!”

Surprisingly, alarm power has very little influence on battery size. Kincaid goes on to explain, “Alarm times are given to be 5 minutes (.083 hours) for horn/strobe systems and 15 minutes (.25 hours) for voice (speaker) systems. If a technician determined that 10 amperes of alarm power were needed, it would only add roughly 1 Amp Hour for a horn/strobe system (10 amperes x .25 hours).”

Integrated Fire Protection understands that correct battery sizing and maintenance are absolutely necessary to ensure reliable Fire Alarm System response. It is our priority to insure that if an incident occurs, and the power goes out, the Fire Alarm will sound and function as it was designed. At Integrated Fire Protection, we would love the opportunity to inspect your facilities’ Fire Alarm System. Our team of certified Fire Alarm experts are ready to assist you at any time of the day or night for any of your Fire Alarm maintenance, repairs, or service needs.

As a Fire and Life Safety Total Solutions Provider, Integrated Fire Protection handles Inspections, Testing, and Maintenance of Fire Extinguishers, Fire Sprinklers, Special Hazard Systems, Suppression Systems, Fire Alarm Systems, Access Control, Video Surveillance, Backflow Prevention, and more. Our goal is to deliver our products and services with an unsurpassed level of professionalism and to take a consultative approach to keeping our clients’ facilities safe and compliant with NFPA codes.

Kincaid, Scott. “Selecting the Correct Battery Size for Fire Alarm Systems.” Brooks Equipment Hot Topics 3rd Quarter 15.3 (2016): 2+. Brooks Equipment, 2016. Web. 26 July 2016.