6kA MCB – 40A 1 Pole C Curve (WMC140C)

The WMC140C is a 40 A single-pole 6 kA Miniature Circuit Breaker (MCB) designed for sub-mains, plant feeds and high-load circuits where inrush currents from motors or transformers could trip a B-curve device. Its C-curve tripping profile (5–10 × In) provides extra surge tolerance while ensuring rapid disconnection under fault conditions.

Tested to BS EN 60898, the WMC140C fits all Whitecliffe consumer units and standard DIN-rail enclosures. It delivers a 6 kA breaking capacity and 20 000-cycle mechanical life for dependable performance in domestic and light-commercial applications.

• 40 A rated current with C-curve (5–10 × In) tripping profile
• 6 kA breaking capacity at 230/400 V AC
• Single-pole design – 18 mm module width
• DIN-rail mounted for consumer units and distribution boards
• Complies with BS EN 60898 and BS 7671 (18th Edition A2)
• Service life – 20 000 mechanical / 8 000 electrical operations

The WMC140C delivers 6 kA short-circuit and overload protection for feed and equipment circuits with moderate inrush. For resistive loads use a B Curve MCB, or add earth-fault protection with our Type A RCBOs.

• Part Code: WMC140C
• Type: Single Pole MCB
• Rated Current (In): 40 A
• Curve: C (5–10 × In tripping characteristic)
• Rated Voltage (Ue): 230/400 V AC
• Rated Frequency: 50/60 Hz
• Breaking Capacity (Icn): 6 kA
• Insulation Voltage (Ui): 500 V
• Impulse Withstand (Uimp): 4 kV
• Dielectric Test Voltage: 2 kV for 1 minute
• Thermal Reference Temp: 30 °C
• Operating Temperature: –5 °C to +40 °C (avg < 35 °C)
• Mechanical Life: 20 000 operations
• Electrical Life: 8 000 operations
• Mounting: 35 mm DIN rail (1 module width)
• Standards: BS EN 60898; BS 7671:2018 (A2)
• Typical Applications: Sub-mains, plant feeds and equipment with high inrush current

Install the WMC140C by a qualified electrician within a suitable consumer unit or distribution board. Ensure the rating and curve match the circuit design and load characteristics.

• Securely mount on 35 mm DIN rail and verify busbar alignment
• Use C-curve for motors, compressors and feed circuits with inrush current
• Check Z_s and voltage drop against BS 7671 limits
• Tighten terminals to manufacturer torque spec and record test results

Where is a 40 A C Curve MCB used?

Typically on sub-mains and plant feeds serving equipment with higher startup currents such as motors or compressors.

Is the WMC140C compatible with Whitecliffe boards?

Yes – it fits all Whitecliffe consumer units and standard DIN-rail enclosures.

Can I use this breaker for industrial loads?

Yes, within its 6 kA fault rating. For higher fault-level sites, use our 10 kA MCBs.

What is the difference between B and C curves?

B-curve devices trip at 3–5 × In for domestic circuits; C-curve trip at 5–10 × In for motors and transformers.

Do you supply D Curve options?

Yes – Type D (10–20 × In) MCBs for heavy industrial loads are available on request.