Power Supply & Battery Calculations
Primary and secondary power requirements, standby duration, battery sizing, temperature derating, load calculations, NAC expanders, and remote power supplies.
- Explain primary and secondary power requirements for fire alarm systems
- Calculate standby and alarm duration requirements for household and commercial systems
- Size batteries with temperature derating factors
- Describe NAC expanders, booster panels, and remote power supply applications
Lección 1
Primary & Secondary Power Requirements
Dual Power Sources
Fire alarm systems require two independent power sources to ensure operation during any single point of failure:
Primary Power
Source: Building AC supply
Circuit: Dedicated, locked breaker
Marking: Red-marked breaker, labeled
Sharing: No other loads on circuit
Secondary Power
Source: Batteries or generator + batteries
Capacity: 24 hours standby + 5 min alarm
Monitoring: Trouble signal on AC loss
Transfer: Automatic, no interruption
Primary Power Requirements
- Must be a dedicated branch circuit serving only the fire alarm system
- Circuit breaker must be locked in the ON position or in a locked cabinet
- Breaker must be red-marked and labeled "FIRE ALARM"
- Must not be on a switched circuit or GFCI
- Power disconnect must generate a trouble signal at the panel
Secondary Power Requirements
- Batteries are the standard secondary power source
- Must provide automatic transfer with no interruption of fire alarm operation
- Battery voltage must be monitored - low voltage generates a trouble signal
- Batteries must be recharged within 48 hours after full discharge
Important
The fire alarm primary power circuit must be dedicated and the breaker locked ON or in a locked panel. Loss of primary power must generate a trouble signal - never a silence.
Fire alarm systems need two power sources: dedicated AC (locked breaker, red-marked) and batteries (automatic transfer). Loss of either source generates a trouble signal. The circuit must serve only the fire alarm system.