Difference Between MCB and RCBO

In this post, we will learn the difference between MCB and RCBO.

Circuit breakers are an essential part of the electrical circuit. It is a device that is used as a protective switch for passing electrical current with tripping conditions checked. When it detects a trip condition, the breaker opens its contact and isolates the input and output voltage from contacting each other.

Many types of circuit breakers are used in a circuit; but in this post, we will focus on two of the most used ones – MCB and RCBO.

Difference between MCB and RCBO

Difference between MCB and RCBO

We will see the difference between both of them in this post. Many get confused in its naming convention and consider both of them as equal. But, there are considerable differences between both of them.

  • MCB stands for Miniature Circuit Breaker and RCBO stands for Residual Current Breaker with Overcurrent.
  • MCB is used to protect against overload and short-circuit. But, RCBO is used to protect against earth leakage fault current with over-current also. Many do not know the exact meaning of earth leakage fault; let us understand it first. In a normal circuit, line and neutral currents will always be equal and balanced. But, whenever there is an earth leakage, as the leakage current flows through the earth, there will be an imbalance in both these currents as the line current will be higher than the neutral current. This difference in current is called residual current.
  • The major difference that separates both circuit breakers is that RCBO has the additional protection of earth leakage current. Basically, it majorly uses microcontrollers and it can also be said as a combination of MCB and RCCB. That is why; it is more useful than MCB; because MCB does not provide protection against the earth-leakage current.
  • MCB is selected based on the load, maximum short-circuit current it can interrupt, and trip curve. RCBO too is selected on the basis of these three things; but apart from that, it also considers maximum leakage current.
  • Cost-wise, RCBO is costlier than MCB.
  • MCB is used to protect lighting circuits, air conditioners, and other home appliances; but RCBO is used mainly to interrupt power to water heaters, power sockets, etc. where there is the possibility of electric shocks to humans.
  • MCB does not provide protection against electric shocks to humans, but RCBO provides protection against electric shocks. This is because the role of RCBO is primarily to detect earth leakage and trip the circuit when detected. Earth leakage is dangerous for the human body. Typically, the human body can withstand a shock of 30mA. After this, it can lead to paralysis or even death for weaker human hearts. And, earth leakage current typically starts from 10mA and can go beyond 30mA.
  • The breaking capacity of RCBO is much higher than MCB (typically up to 10kA).
  • Some RCBO’s also have indicators on them to show any earth fault trip. This feature is very helpful as it quickly aides the engineer in troubleshooting faults. Such a feature is not available in MCB’s.

These are the differences between MCB and RCBO. It must be up to the electrical engineer to decide what to choose if he knows the basic requirements and functions.

About the author

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Electronics Engineer with 8+ years of experience in industrial automation. Blogging is my hobby and I write articles and blogs on industrial automation.

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