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Residual Current Circuit Breaker, How it Works and Use

Residual current circuit breaker
Residual current circuit breaker
Resource: https://www.youtube.com/watch?v=OvQsZ7ImeEM

The residual current circuit breaker, as its name implies, helps guard against electrical shocks during a leakage current. It works by separating the system from the main supply when current imbalance occurs, thereby preventing damage or injury. Read this post to learn more about the residual current circuit breaker, how it works, its purpose, and even price.

What is a Residual Current Circuit Breaker?

To begin with, here’s the residual current circuit breaker definition: Residual current circuit breaker is the name given to a type of breaker that will trip to prevent shock or electrocution. This happens when the current flowing in the live wire (incoming) and that of the neutral wire (outgoing) does not match.

In a normal situation, the incoming currents must remain equal. In the event of a fault, a deviation from the normal will occur. Therefore, a residual current circuit breaker, RCCB, is an electrical protection device that’s designed to detect and react to this change.

A leakage current may occur when electricity in the live wire finds an alternative path, say the body of a human if they happen to touch a live conductor via faulty electrical equipment. In such cases, RCCB will trip and break the circuit to protect the person from getting electric shock.

What Does a Residual Current Circuit Breaker Do?

A residual current operated circuit breaker is designed to protect people from severe electric shocks by disconnecting the system from the main power supply. It helps prevent fires that fault currents may cause. Sometimes, this RCCB comes with an additional overload protection for extra safety. The purpose of this type of breaker and its overprotection feature is explained below.

Residual Current Circuit Breaker function

The main residual current circuit breaker function is to detect a change in the outgoing current that electric leakage may cause. While there’s usually a small leakage due to insulation wear and other causes, any significant change indicates a potentially dangerous situation.

The amount of current that the residual circuit breaker measures is usually in the order of 10-100mA, depending on the type of system it is being used for. In typical situations, a human body can be exposed to electric shocks at as low as 30mA, so the RCCB trips and disconnects the system before it reaches this level.

Residual Current Circuit Breaker with Overload Protection

Some RCCBs are fitted with an additional overload protection which helps detect and disconnect the system when it is overloaded. A residual current circuit breaker with overload protection is usually abbreviated as RCBO.

This type of breakers could be taken to be a residual current circuit breaker and MCB (miniature circuit breaker combined). It has the ability to protect against electrical shock and fire due to earth faults, as well as the effects of overcurrent.

Residual current circuit breaker working principle illustrated
Residual current circuit breaker working principle illustrated
Resource: https://www.youtube.com/watch?v=CL1zIVWvr9g

How Does a Residual Current Circuit Breaker Work?

A residual current operated circuit breaker works by measuring the current leaving its terminal and comparing it with the current returning to its terminal. Once an imbalance is detected, the breaker trips and disconnects the power supply from the system. To help you understand this process better, we’ll first look at the construction of RCCBs then explain their working principle.

Residual current Circuit Breaker Diagram

As you can see from the residual current circuit breaker diagram above, the breaker consists of a As you can see from the residual current circuit breaker diagram above, the breaker consists of two parts; a core balancing current transformer and a switching device.

The current transformer measures the amount of current flowing in the circuit and when it surpasses a preset threshold a limit, it triggers the switching device to open the circuit, thereby stopping the flow of electricity during a fault condition.

Residual Current Circuit Breaker Working Principle

The residual current circuit breaker working principle is typically based on the different of current in the live and neutral circuit of the system. According to a law called Kirchhoff’s Law, the total current entering a node must be equal to the total current leaving the node.

When this is not true (due to an imbalance) it means that there is leakage of current somewhere in the system. This can lead to electrical shocks if left unchecked, or even a fire. The RCCB breaker monitors the two points and trips if a certain amount of change is detected.

Using a residual current circuit breaker in an electrical system
Using a residual current circuit breaker in an electrical system
Resource: https://www.electriciansforums.net

Residual Current Circuit Breaker Advantages

The RCCB is an important safety component in any electrical system, especially those that involve residential or commercial buildings. Apart from providing protection against electric shocks, other residual current circuit breaker advantages include the following:

  • Since these devices are designed to trip immediately on sensing a fault, they can help prevent damage to expensive electronic equipment.
  • RCCBs are very effective in preventing fires caused by electrical faults.
  • A residual current circuit breaker will usually come with a test button. This helps you ensure that the RCCB is working correctly.
  • Residual current circuit breakers come in an array of sizes and ratings, making them suitable for a variety of applications.
  • They are relatively easy to install and don’t require complicated wiring.

The above residual current circuit breaker advantages notwithstanding, it helps to ensure your RCCB is adequately rated for the system it is used in. This rating depends on the size of the wiring and load connected, as well as its capacity.

With this information, you can choose an appropriately rated RCCB for optimal protection. Plus, unless your RCCB comes with an overload protection feature, it remains important to install a separate overload protector. This will help protect your system from overcurrents.

Residual Current Circuit Breaker Price

The residual current circuit breaker price ranges depending on the type of RCCB, its capacity, and other features. Generally, however, they are usually quite affordable and can be found in most electrical supply stores, both online and physical.

The range of RCCB price will usually start at around $30 and can go up to about $100 or higher. The exact price will depend on the features and capacity of the RCCB, such as its amperage rating. The higher the amperage rating, the more expensive it is likely to be.

It’s important to note that many other factors can also come into play when determining residual current circuit breaker prices, such as tripping capabilities. For example, a type B RCCB will be more expensive than a type A as it can detect and respond to more types and levels of fault currents.

Ensure that you get an RCCB that meets the safety standards of your region, so be sure to check with your local electrical code. Also, it’s a good idea to research and compare prices between different brands and models before making your purchase.


Residual current circuit breakers, RCCBs, are a vital safety feature in an electrical system. They prevent electric shocks, which can be fatal, by detecting any imbalances in the live and neutral circuits. RCCBs can also prevent fires that may result from leakage currents. When selecting an RCCB for your system, be sure to choose one that is adequately rated and has all the features you need.

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