Fire Alarm Standby Battery Calculator For House

Standby Capacity Formula:

\[ \text{Standby Capacity (Ah)} = \text{House Standby A} \times 24 \times \text{Margin} \]

Standby Capacity (Ah):

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1. What is Standby Capacity?

Standby capacity refers to the battery capacity required to maintain a fire alarm system during power outages. It ensures the system remains operational for the required standby period (typically 24 hours) plus a safety margin.

2. How Does the Calculator Work?

The calculator uses the standby capacity formula:

\[ \text{Standby Capacity (Ah)} = \text{House Standby A} \times 24 \times \text{Margin} \]

Where:

House Standby A — Current drawn by the system in standby mode (amps)
24 — Required standby duration in hours
Margin — Safety factor (typically 1.25-1.5)

Explanation: The formula calculates the total amp-hours needed to power the system for 24 hours with an additional safety margin.

3. Importance of Proper Standby Calculation

Details: Accurate standby capacity calculation is crucial for fire safety compliance and ensuring the fire alarm system remains operational during power outages.

4. Using the Calculator

Tips: Enter the system's standby current in amps and the desired safety margin (typically 1.25). Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical house standby current?
A: Most residential fire alarm systems draw between 0.1A to 0.5A in standby mode.

Q2: Why include a margin?
A: The margin accounts for battery aging, temperature effects, and unexpected load increases.

Q3: How long should batteries last?
A: Fire alarm batteries should provide at least 24 hours of standby power plus 5 minutes of alarm.

Q4: When should batteries be replaced?
A: Typically every 3-5 years, or when capacity drops below 80% of rated capacity.

Q5: Are there code requirements for this calculation?
A: Yes, NFPA 72 and local fire codes specify requirements for standby power calculations.