1. What is Breaker Size Calculation?

The breaker size calculation determines the appropriate circuit breaker amperage needed to protect an electrical circuit. The 1.25 multiplier provides a safety margin to prevent nuisance tripping while ensuring protection.

2. How Does the Calculator Work?

The calculator uses the standard breaker sizing formula:

Where:

• \( I \) — Continuous current load in amperes
• 1.25 — Safety factor (125% of continuous load)

Explanation: The National Electrical Code (NEC) requires circuits to be protected at 125% of continuous loads (those lasting 3+ hours).

3. Importance of Proper Breaker Sizing

Details: Correct breaker sizing prevents electrical fires by ensuring overcurrent protection while avoiding nuisance tripping during normal operation.

4. Using the Calculator

Tips: Enter the continuous current load in amperes. The calculator provides both the calculated minimum size and the next standard breaker size.

5. Frequently Asked Questions (FAQ)

Q1: Why multiply by 1.25?
A: The 1.25 factor accounts for continuous loads (3+ hours) as required by NEC to prevent overheating.

Q2: What are standard breaker sizes?
A: Common residential sizes: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200 amps.

Q3: Can I use a larger breaker than calculated?
A: Never exceed the ampacity of the conductors. Breakers protect wires, not devices.

Q4: What about motor loads?
A: Motors require different calculations accounting for starting current - consult NEC Article 430.

Q5: Does this apply to DC circuits?
A: DC breaker sizing has different considerations - consult manufacturer specifications.