B10 vs B16 Circuit Breaker? Simple Rule: 1.5mm²→B10, 2.5mm²→B16

Circuit breakers (technically: miniature circuit breakers or MCBs) protect your electrical installation from damage due to overload or short circuit. Circuit breaker selection isn't guesswork – it's governed by strict rules of physics and electrical standards.

The best results come when breaker sizing is done inside a full electrical design workflow, not as an isolated rule-of-thumb check after cables have already been chosen.

The Golden Rule of Selection

The most important rule is: Select the protection device for the cable, and the cable for the load. Never the other way around! Installing a larger breaker when it "keeps tripping" without upgrading the cables is a direct path to fire.

Which Breaker for Which Cable?

In typical domestic installations (concealed wiring):

• Lighting (1.5mm² cable): B10 breaker (10A). Sometimes B6. Using B16 with 1.5mm² cable is often a mistake, though it depends on installation method.
• Sockets (2.5mm² cable): B16 breaker (16A). This is standard for general socket circuits.

If you are still unsure about conductor sizing, verify it with the cable selection guide before finalizing the breaker.

B or C Characteristic?

The letter before the amperage (e.g., B16) indicates the time-current characteristic.

• B (fast): Standard for homes. Protects resistive devices (heaters, bulbs) and cables.
• C (time-delayed): Used for devices with high inrush current (motors, welders, large transformers). Rarely used in homes, perhaps in garages.

Motor-driven equipment is the main exception. For a dedicated heat pump electrical installation, for example, C-characteristic devices are often more appropriate than standard B-curve breakers.

Our system in Electro Planner has a built-in algorithm that suggests correct circuit breaker selection based on circuit type, device power, and cable assumptions, making it easier to keep planning and documentation consistent.