Legrand MCB and PULS ECB - MCBs vs ECBs - which is best for securing a DC circuit?

2025-06-17

MCBs vs ECBs: Which is best for securing DC circuits?

In DC circuits, two primary forms of protection are commonly used: MCBs (Miniature Circuit Breakers) and ECBs (Electronic Circuit Breakers).

Choosing the right circuit breaker requires a clear understanding of the application, careful system planning and often requires significant engineering resources.

Each time the application changes, it’s necessary to reassess whether the existing circuit breaker still provides adequate protection for the connected loads.

Learning hub

MCBs – How they work

Miniature circuit breakers are electrical switches that trip when excessive current is flowing, to prevent damage to electrical circuits. When an overload or short circuit is detected MCBs automatically trip to interrupt the flow of electricity.

MCBs typically use a bimetallic strip or magnetic coil to detect overcurrent conditions. This strip heats up and bends under excessive current, tripping the switch and interrupting the circuit. For short circuits, a magnetic coil generates a strong field to trip the switch, quickly cutting off current.

Legrand miniature circuit breaker DX3 series

Puls PISA series electronic circuit breaker

ECBs – How they work

Electronic circuit breakers use electrical components and controllers to detect and interrupt current in a circuit. ECBs switch much faster than traditional circuit breakers and offer more precise control over current limitation, improving protection of sensitive loads.

ECBs use components to monitor the flow of current in a circuit. When the current exceeds a predetermined limit, the controller detects a fault, overload or short circuit. A MOSFET switch is then triggered interrupting the flow of current and protecting the circuit and load. The breaker can then be reset for continued operation once the fault is resolved.

Advantages & Disadvantages of MCBs and ECBs

Advantages of MCBs

Compact and lightweight - Designed to be small and lightweight, meaning they are easy to install in confined spaces or where weight is a concern.
Quick acting and highly sensitive - MCBs act quickly when a fault is detected, interrupting flow within milliseconds, as well as being highly sensitive to detecting even minor overloads and short circuits.
Reliable - Reliable and consistent performance in protecting electrical equipment and systems, preventing electrical fires, wire degradation and appliance damage.
Easy installation and maintenance - MCBs are easy to install into electrical circuits and can be reset easily after tripping.

Advantages of ECBs

Temperature independent - The modules can also be installed in a control cabinet without minimum spacing from other units and only a minimum distance of 15 mm to heat sources.
Compact - Although MCBs are also compact and lightweight ECBs are even smaller and lighter.
Adjustable - ECBs often allow for adjusting the current value at which they trip, offering greater flexibility in application.
Precision and speed - ECBs typically react faster and more precisely when compared with MCBs, since they do not reply on a thermal or magnetic mechanisms and continuously monitor current.

Disadvantages of MCBs

Breaking capacity - MCBs generally have a lower breaking capacity compared to ECBs, so cannot handle higher fault currents
No earth protection - Primarily protecting against overcurrent and short circuit, additional devices may be required to protect against earth leakage faults.
Original designed for AC - MCBs were originally designed for AC applications, therefore they require multiple times the nominal current for a few milliseconds to trip.
Temperature Dependant - The bimetal responsible for tripping is temperature dependent. This means: the higher the ambient temperature, the more the bimetal heats up and trips earlier.

Disadvantages of ECBs

Cost - ECBs generally cost more than MCBs in hardware and installation costs, as they may require more specialised skills to install.
Susceptible to damage - ECBs can be more susceptible to damage, if not well maintained or connections are loose.
Dependent on electricity - Susceptible to failure due to electrical issues, power surges and electromagnetic interference.
Additional components required - ECBs require other components such as power supplies to function, increasing complexity and installation time and cost.

Comparing typical attributes of MCBs & ECBs

See the info graphic below which compares some typical attributes of MCBs and ECBs for an easy comparison of the two devices.

Typical applications of MCBs & ECBs

mcbs applications

Automotive manufacturing using miniature circuit breakers

MCBs in DC applications are typically used to protect against overcurrent and short circuits, in low voltage applications. They can be commonly used in solar power generation, automotive electronics, ship electrical systems and industrial machinery.

ECBs applications

Wind turbines - renewable energy with electronic circuit breakers

ECBs have many uses in DC circuits, protecting against overcurrent and faults. They are particularly useful in constant DC flow applications, including renewable energy, transportation and industrial power applications.

Summary

When choosing DC circuit breakers your application and requirements should be carefully considered.

MCBs use a bimetallic strip or coil to trip a circuit in the event of overcurrent and short circuits. These are more suited to low voltage, less complex applications.

ECBs use electronic monitoring to trigger a switch and interrupt the flow of current, protecting the circuit and load. Ideal for constant DC flow applications and sensitive loads.

Choosing a trusted manufacturer

At OEM Automatic, we supply high-quality MCBs and ECBs from trusted manufacturers including Legrand and Puls. Contact our experts for help with your DC circuit application.

Need Help with a DC Circuit Application?

Our Panel team is ready to assist with expert advice, product recommendations, and proof-of-concept support.

Phone: 0116 284 9900

Email: [email protected]

Live chat: Available on our website

Onsite support: Book a visit with one of our experienced engineers for demonstrations and application advice - email [email protected] to arrange a visit.