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.
16A 2 Pole 10kA MCB – B Curve (WKC216B)
£7.49
The WKC216B is a 16A 2 Pole 10kA Miniature Circuit Breaker (MCB) designed for dependable short-circuit and overload protection in small power and lighting applications. With a B-curve tripping characteristic and double-pole isolation, it’s ideal for heating circuits, immersion heaters, control gear, and general sockets...
WKC 3 Pole 10kA MCB – 6A B Curve (WKC306B)
£21.30
The WKC306B 3 Pole 10kA MCB is a compact B Curve breaker rated at 6A, designed to protect three-phase circuits from overload and short-circuit faults. Built with a 10kA breaking capacity, it’s ideal for commercial and industrial distribution boards, EV chargers, and solar PV systems....
WKC 3 Pole 10kA MCB – 63A B Curve (WKC363B)
£21.30
The WKC363B 3 Pole 10kA MCB is a 63A B Curve breaker engineered to protect heavy-duty three-phase circuits from short-circuit and overload faults. With a robust 10kA breaking capacity and full compliance to BS 7671 (18th Edition), it’s trusted in industrial distribution boards, EV charger...
WKC 3 Pole 10kA MCB – 50A B Curve (WKC350B)
£21.30
The WKC350B 3 Pole 10kA MCB is a 50A B Curve breaker providing reliable short-circuit and overload protection for three-phase circuits. Rated at 10kA breaking capacity and compliant with BS 7671 (18th Edition), it’s a trusted solution for industrial boards, EV installations, and solar PV...
WKC 3 Pole 10kA MCB – 20A B Curve (WKC320B)
£21.30
The WKC320B 3 Pole 10kA MCB is a 20A B Curve breaker designed to protect three-phase circuits against overloads and short circuits. With a 10kA breaking capacity and compliance to BS 7671 (18th Edition), it’s a trusted choice for industrial boards, EV charger setups, and...
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.