Overview

The 6kA 40A Miniature Circuit Breaker is engineered as a high-capacity protection device specifically designed for demanding electrical circuits that draw significant continuous current. With a 40-amp rating, this MCB is the preferred choice for heavy-duty applications including large electric showers, instantaneous water heaters, commercial catering equipment, industrial machinery, EV charging points, and sub-main distribution circuits. The 6kA breaking capacity ensures robust protection against both overcurrent events and catastrophic short-circuit faults, safely interrupting fault currents up to 6,000 amperes without compromising the integrity of the breaker or the safety of the installation.

Manufactured to meet rigorous international standards, this 40A MCB complies fully with IEC60898-1 and holds both CE and UKCA certifications, making it legally compliant for installations throughout the United Kingdom and European markets. The thermal magnetic trip mechanism provides two distinct layers of protection: the thermal bimetal element responds to sustained overloads by mimicking cable heating curves, while the electromagnetic coil reacts instantaneously to short-circuit conditions. With a versatile design supporting 1, 2, 3, or 4-pole configurations, 50/60Hz frequency operation, and compatibility with 35mm DIN rail mounting systems, this circuit breaker delivers professional-grade protection for any high-current electrical installation requiring dependable overcurrent safeguarding.

Why Choose a 6kA 40A Miniature Circuit Breaker

Selecting a 40A rated MCB is essential when standard 32A protection would be insufficient for your equipment or circuit demands. This higher current rating makes the breaker perfectly suited for dedicated circuits powering 8.5kW to 9.5kW electric showers, large commercial ovens, three-phase industrial motors up to 15kW, workshop machinery, and electric vehicle charging points requiring Type 2 protection. The 6kA breaking capacity provides a substantial safety margin above typical domestic fault current levels, ensuring the breaker will safely clear even severe short-circuit events without welding contacts or rupturing its housing. Unlike fuses that require replacement after every fault, this resettable MCB can be simply switched back on after addressing the underlying issue, reducing downtime and maintenance costs significantly.

Furthermore, the thermal magnetic trip mechanism offers two distinct layers of protection that work in harmony. The thermal element uses a bimetal strip that bends gradually under sustained overcurrent, mimicking the heat buildup in your wiring and tripping only when dangerous temperatures are reached. The magnetic element operates nearly instantaneously during short circuits, limiting let-through energy and protecting sensitive electronics downstream. With multiple trip curve options (B, C, and D curves available), you can precisely match the breaker's response characteristics to your specific load type—whether that is resistive heating loads, motor-driven equipment with startup surges, or transformer-coupled devices. This level of customization, combined with UKCA and CE certification, makes this 6kA 40A MCB a professional-grade choice for any electrical installation requiring dependable, code-compliant overcurrent protection for higher-amperage circuits.

Key Features

• 40 Ampere Rated Current – Specifically designed for high-power circuits including electric showers, ovens, and industrial machinery

• 6kA Breaking Capacity – Safely interrupts short-circuit currents up to 6,000 amperes for comprehensive protection

• Thermal Magnetic Trip Mechanism – Combines bimetal thermal overload protection with electromagnetic short-circuit interruption

• Dual Certification – Fully compliant with IEC60898-1 standards and certified CE and UKCA for regulatory compliance

• Versatile Pole Configurations – Available in 1P, 2P, 3P, and 4P options to suit single-phase and three-phase systems

• Contact Status Indication – Clear visual indicator window shows whether contacts are open or closed at a glance

• DIN Rail Mounting – Standard 35mm rail design enables quick installation in existing consumer units and distribution boards

• High Cycle Life – Rated for 10,000 electrical operations and 20,000 mechanical operations for lasting durability

• Wide Temperature Tolerance – Operates reliably from -35°C to +70°C for various environmental conditions

• Multiple Trip Curves – Available in B, C, or D characteristics to match specific load requirements

Technical Specifications

• Product Type: Miniature Circuit Breaker (MCB)

• Rated Current: 40 Amperes

• Breaking Capacity: 6kA (Ics & Icn)

• Number of Poles: 1P, 2P, 3P, 4P (selectable)

• Rated Frequency: 50/60 Hz

• Frame Current: 63A

• Rated Voltage: AC240V (1P) / AC415V (multi-pole)

• Rated Insulation Voltage: 690V

• Rated Impulse Withstand Voltage: 4kV

• Trip Characteristics: B, C, D Curves available

• Trip Form: Thermal magnetic trip

• Pollution Level: 2

• Electrical Life: 10,000 operations

• Mechanical Life: 20,000 operations

• Protection Grade: IP20

• Storage Temperature: -35°C to +70°C

• Installation Site Altitude: ≤2000m

• Terminal Type: Fixed with screw

• Maximum Wiring Capacity: 25mm²

• Maximum Limit Torque: 2.5 Nm

• Installation Category: Class II, III

• Installation Method: 35mm standard DIN rail

• Incoming Method: Upper and lower terminals

• Standards Compliance: IEC60898-1

• Certifications: CE, UKCA

Frequently Asked Questions

1. What type of circuit requires a 40A MCB rather than a 32A?
A 40A MCB is required for circuits where the continuous load exceeds 32A. Typical applications include 8.5kW+ electric showers (which draw approximately 37A), large commercial ovens, industrial machinery, electric vehicle charging points, and sub-main distribution circuits feeding smaller consumer units.

2. What is the maximum cable size I can connect to this 40A MCB?
This MCB accepts wiring up to 25mm². For a 40A circuit, the minimum recommended cable size is 6mm² for standard installations, though 10mm² is often preferred to reduce voltage drop. Always consult local wiring regulations for specific cable sizing requirements based on installation method and length.

3. Can I use this 40A MCB for a three-phase motor?
Yes, select the 3-pole version of this MCB for three-phase motor applications. For a 40A rating on a 400V three-phase system, this would typically protect motors up to approximately 22kW. Choose C-curve for standard motor starting or D-curve for high starting current applications.

4. What is the difference between B, C, and D curves on this 40A MCB?
B-curve (3-5x 40A = 120-200A) trips quickly for resistive loads like heating elements. C-curve (5-10x 40A = 200-400A) handles moderate inrush from motors and lighting. D-curve (10-20x 40A = 400-800A) is for high inrush applications like large transformers or welding equipment.

5. How do I reset this MCB after it trips?
First, identify and resolve the fault causing the trip (overload or short circuit). Then, push the toggle lever fully down to the OFF position, then back up to the ON position. If the MCB immediately trips again, the fault remains and requires professional investigation. The indicator window shows red when ON and green when OFF or tripped.