Power Supplies

$ 29.00

Continuing Education Units (CEU): 0.10

Expected Duration: 1 Hour

This self-paced online course covers the fundamentals of the power supplies used in fire alarm systems. The course reviews the power supply requirements for all systems and the importance of power supply requirements in system design.

Upon completion you should be able to:

  • Explain the requirements for the installation of primary power supplies
  • Describe the allowable arrangements for the installation of secondary power supplies, as well as different required arrangements for when the secondary power supply uses batteries, generators or some combination of the two
  • List the secondary power capacity requirements for different types of alarm systems
  • Explain the requirements for the installation of an uninterruptible power supply
  • List the allowable time for transition from primary to secondary power supplies
  • List the allowable time for fire alarm system batteries to re-charge
  • Review battery calculations for accuracy

Who Will Benefit

Anyone whose job involves designing, reviewing, evaluating or installing fire protection systems, including: designers, installers, engineers, electrical contractors, technicians, project managers, fire marshals, and architects

Course Summary

  • Each fire alarm system has a specific design that is never 100% generic. The goals of the system - Life Safety, Property Protection, Mission Continuity, Heritage Preservation, or Environmental Protection - directly impact the design.
  • The power supply is the first component of the fire alarm system. Like other electrical installations, the power supply must conform to the National Electrical Code (NFPA 70). A fire alarm system needs two independent power supplies, a primary and a secondary. Primary power normally connects to the building's light and power service. The secondary (or backup) power supply may be as simple as control-unit battery power or as complex as a combination of batteries and an engine driven generator. In the past, secondary power requirements could sometimes be eliminated. However, this required an extremely reliable primary power supply and a generator. Secondary power elimination is no longer allowed, as of the publication of NFPA 72-2007.  It was allowed in systems installed prior to the adoption of NFPA 72-2007, but only when the power supply conformed to the National Electrical Code, Articles 700, 701 or 702.
  • The fire alarm control unit requires a dedicated primary power circuit. This means that the fire alarm system's connection to the light and power service cannot be shared; the control unit must be the only connection on this circuit. The circuit breaker (or other circuit-disconnecting device) must have controlled access so that only authorized people can operate it. Circuit-disconnecting devices must be clearly marked in red at the circuit control, and the location of the circuit breaker must be identified at the fire alarm control panel.
  • Secondary power requirements state that within 10 seconds after the primary power fails the secondary power supply must power the system. However, no signals can be lost. The backup power supply must keep the system in service for a specified period of time. That period varies with system classification. If the alarm system is a remote station or auxiliary station system, the requirement is 24 hours, but in older systems, this may be 60 hours. If the system is a protected premises, central station, or proprietary supervising station system, the batteries will be required to power the system for a period of 24 hours. For any system classification, the backup power supply has to provide power for at least five minutes of full alarm activity.
  • Some properties may use an emergency voice/alarm communication system. Such systems require 24 hour standby in quiescent operation, but the standby power must also provide 15 minutes of operation at maximum connected load.
  • Transfer of power from primary to secondary has to occur so that system functions will not be lost.
  • Allowable arrangements for secondary power are storage batteries, multiple generators, or a generator and batteries.
  • Secondary power supplies have special requirements for readiness. Batteries used in a secondary power supply must be kept charged, which must be completed in 48 hours or less when batteries are fully discharged. If the charging process fails, the system must initiate a trouble signal.  Batteries must be marked with their date of manufacture.
  • Compatibility is a big issue with fire alarm system initiating devices. Underwriters Laboratories and FM Global keep a list of alarm system components and their ability to interface with other components.