B Curve MCBs for Standard Domestic Circuits
B Curve MCBs are miniature circuit breakers designed for circuits with low inrush currents and predictable load behaviour. They are the default choice for most domestic and light commercial installations, providing fast overcurrent and short-circuit protection for lighting, socket and general-purpose circuits.
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B curve devices trip between three and five times their rated current, giving them a quick response to faults while remaining stable under normal operating conditions. They are available across a full spread of current ratings and breaking capacities, allowing installers to match protection to both the supply fault level and the connected load.
- B curve tripping characteristics for low-inrush circuits
- Ideal for lighting and socket circuits in homes and small workplaces
- Available in multiple ratings from 6A upwards
- 6kA and 10kA options to suit different fault levels
- Single-module DIN-rail format for fast installation and replacement
B Curve MCBs are widely used in new builds, rewires and consumer unit upgrades where the prospective fault current and load profile fall within standard domestic ranges.
1 Pole 10kA MCB 40A B Curve WKC140B
£5.00
The WCED WKC Series 10kA Miniature Circuit Breakers (MCBs) are high-performance devices designed for precise overcurrent detection and short-circuit protection. Built to handle demanding applications, they provide reliable protection for domestic, commercial, and industrial distribution systems – including solar PV with SPD and EV charging...
1 Pole 10kA MCB 32A B Curve WKC132B
£5.00
The WCED WKC Series 10kA Miniature Circuit Breakers (MCBs) are high-performance devices designed for precise overcurrent detection and short-circuit protection. Built to handle demanding applications, they provide reliable protection for domestic, commercial, and industrial distribution systems – including solar PV with SPD and EV charging...
1 Pole 10kA MCB 20A B Curve WKC120B
£5.00
The WCED WKC Series 10kA Miniature Circuit Breakers (MCBs) are high-performance devices designed for precise overcurrent detection and short-circuit protection. Built to handle demanding applications, they provide reliable protection for domestic, commercial, and industrial distribution systems – including solar PV with SPD and EV charging...
1 Pole 10kA MCB 16A B Curve WKC116B
£5.00
The WCED WKC Series 10kA Miniature Circuit Breakers (MCBs) are high-performance devices designed for precise overcurrent detection and short-circuit protection. Built to handle demanding applications, they provide reliable protection for domestic, commercial, and industrial distribution systems – including solar PV with SPD and EV charging...
1 Pole 10kA MCB 10A B Curve WKC110B
£5.00
The WCED WKC Series 10kA Miniature Circuit Breakers (MCBs) are high-performance devices designed for precise overcurrent detection and short-circuit protection. Built to handle demanding applications, they provide reliable protection for domestic, commercial, and industrial distribution systems – including solar PV with SPD and EV charging...
What Is a B Curve MCB?
A B curve MCB is a miniature circuit breaker that trips when the current reaches between three and five times its rated value. This makes it ideal for circuits with low starting currents, where any significant spike is likely to be a genuine fault rather than normal operation.
Where B Curve MCBs Are Used
- General lighting circuits including LED and mixed loads
- Socket and ring main circuits in homes and small offices
- Immersion heaters and other resistive loads
- Small appliance circuits with predictable current draw
- Standard domestic distribution boards where inrush current is low
Why Choose a B Curve Over C Curve?
B curve devices are more sensitive to overcurrent than C curve breakers. This is beneficial on circuits that do not experience high start-up currents, as it ensures faults are cleared quickly while minimising the risk of wiring damage.
- Faster response to overcurrent on low-inrush circuits
- Correct matching to typical domestic load profiles
- Helps protect cable insulation by limiting fault energy
Breaking Capacity & Compliance
B Curve MCBs are available with different breaking capacities, commonly 6kA for standard domestic installations and 10kA for higher fault-level environments. All devices are designed to comply with BS EN 60898 and support 18th Edition Wiring Regulations when correctly selected.
Selecting the Right Rating
The correct rating depends on cable size, installation method and expected load. Typical domestic choices include 6A and 10A for lighting, 16A or 20A for radial circuits, and 32A for ring mains or heavier loads.
Installer Benefits
B Curve MCBs provide dependable, predictable protection across everyday circuits. With a wide range of ratings and breaking capacities, they allow electricians to design safe, compliant boards that match real-world domestic and light commercial installations.