1. What is Main Breaker Size Calculation?

The main breaker size calculation determines the appropriate circuit breaker size for an electrical panel based on the sum of all connected loads, applying a 25% safety margin as required by electrical codes.

2. How Does the Calculator Work?

The calculator uses the standard electrical formula:

Where:

• Sum of Loads — The total current draw of all connected electrical devices
• 1.25 — The 25% safety factor required by electrical codes

Explanation: The 25% safety margin ensures the breaker won't trip under normal operating conditions while still providing overload protection.

3. Importance of Proper Breaker Sizing

Details: Correct breaker sizing is crucial for electrical safety. An undersized breaker may trip unnecessarily, while an oversized breaker may not provide adequate protection against overloads.

4. Using the Calculator

Tips: Enter the total sum of all electrical loads in amperes. The calculator will provide both the calculated size and the nearest standard breaker size.

5. Frequently Asked Questions (FAQ)

Q1: Why is there a 25% safety factor?
A: The 25% margin accounts for potential load variations and ensures the breaker won't trip during normal operation while still providing protection.

Q2: What are standard breaker sizes?
A: Common standard sizes include 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 125, 150, 200A and larger in increments.

Q3: Should I round up or down?
A: Always round up to the next standard size unless the calculated value is exactly a standard size.

Q4: Does this apply to subpanels too?
A: Yes, the same calculation method applies to subpanels, though the main panel breaker must account for all subpanels.

Q5: When should I consult an electrician?
A: For any complex installations, commercial projects, or if your calculated size exceeds 200A, professional consultation is recommended.