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Choosing the right circuit breaker isn’t just a technical decision — it’s a crucial step in protecting your home, office, or facility from electrical overloads, short circuits, and potential fire hazards. Whether you’re setting up a new installation or just want a better understanding of your electrical system, this guide will help you determine the correct breaker size.

Why choosing the right Circuit Breaker Matters

Circuit breakers are safety devices that protect your electrical wiring and equipment.

If a breaker is rated below the required current of the connected load, it may trip unnecessarily even under normal conditions.

If it is rated above the conductor or load capacity, it may fail to trip during an overload, posing a fire and safety hazard.

Three Things to Keep in Mind When Choosing A Circuit Breaker

 1. Calculate Your Load

Start by calculating the total load (in amps) that the circuit will carry.

Use this formula:

Amps = Watts ÷ Volts

Example:

For a 7.5kW (7500W) pump on a 240V supply:

7500 ÷ 240 = 31.25 Amps

This means a 32A breaker can be recommended. But wait!!!!!

 Note: This is the running current. Motor-driven equipment like pumps often have a higher starting current, so you’ll typically need a breaker with additional capacity or a delayed-trip characteristic.

2. Use the 80% Rule

According to the National Electrical Code (NEC), for continuous loads (running for 3 hours or more), circuit breakers should only carry 80% of their rated current.

Example:

If your load is 31.25 Amps as calculated above, and it’s going to be a continuous running load;

31.25A ÷ 0.8 = 39.06A breaker needed or rather a 40Amps Breaker.

3. Choose Compatible Brands

Make sure your breaker is compatible with your distribution board. Reliable brands like Schneider Electric and Siemens are widely used and meet global safety standards.

Common Breaker Sizes by Application

Pro Tip: Always check with a certified electrician before making any final decisions.

What to Avoid

• Don’t guess your breaker capacity — always do the math.
• Don’t ignore local codes — they often have specific rules for breaker ratings.

Need Expert Help?

At Electrical and Automation Switchgears Limited, we stock a wide range of Schneider Electric and Siemens breakers, distribution boards, and electrical accessories for homes, offices, and industries.

Our technical team is ready to help you choose the right products, so you can power your space safely and efficiently.

Reach out today :

Email: sales@automationnigeria.com

You can also send us Direct Messages on all our social media handles.