Miniature Circuit Breakers (MCBs) are automatic electrical safety devices that protect circuits from damage caused by overcurrent and short circuits. Commonly installed in consumer units and distribution boards, MCBs trip when the current exceeds safe levels, helping to prevent overheating, equipment damage, and electrical fires. They typically use thermal and magnetic tripping mechanisms and can be manually reset once the issue is resolved. MCBs are essential for ensuring the safe and reliable operation of residential, commercial, and industrial electrical systems.

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Types of MCBs

MCBs are available in several tripping characteristics — commonly referred to as trip curves — which determine how quickly they respond to overcurrent conditions. While there are various types including A, B, C, D, K, and Z, the most widely used in residential, commercial, and industrial settings are Type B, Type C, and Type D. Each type is designed to suit different levels of expected electrical surge or inrush current based on the application.

• Type B: General purpose, suitable for domestic installations. Trips between 3 and 5 times the load current.
• Type C: Designed for applications with higher inrush currents, such as motors and transformers. Trips between 5 and 10 times the full load current.
• Type D: Intended for circuits with significant inrush currents, like those associated with high-powered equipment. Trips between 10 and 20 times the full load current.

To learn more, take a look at our Complete Guide to MCBs.