Residual Current Circuit Breaker (RCCB)

While electricity has become an indispensable component, it comes with its own hazards. Electrocution and fire being the two major risks. One cannot afford to be negligent when it comes to insulating the equipment.Aimed at protecting a person from the risk of electric shocks and fires, RCCB is helpful. In cases of sudden earth fault, the RCCB ensures that the circuit will trip immediately. The person is thus protected from an electric shock.

What Is RCCB (Residual Current Circuit Breaker) ?

It is a Leakage Current Sensing Device used to protect a Low Voltage Circuit in case of a current flowing through an abnormal path towards earth.An RCCB is an important safety measure. It is a current sensing device, which can measure and disconnect the circuit. It can happen whenever a fault occurs in the connected circuit or the current exceeds the rated sensitivity.

Purpose Of RCCB

RCCB is mostly beneficial in circumstances where there is a sudden earth fault occurring in the circuit. Example – a person meets an open live wire in the circuit. In such situation, in dearth of an RCCB in the circuit, an earth fault could happen. Also, the person is at the risk of receiving an electrical shock.

But, if the same circuit is protected with RCCB, it will trip the circuit in fraction of a second. Thus, preventing the person from getting an electrical shock. So, it is a good and safe practice to install RCCB in your electrical circuit.

Principle Behind RCCB

RCCB works on the principle of Kirchhoff’s law. It states that the incoming current must be equal to the outgoing current in a circuit. RCCB, hence, compares the difference in current values between live and neutral wires. The current flowing to the circuit should be the same for both the live and the neutral wire. In case of a fault, the current from the neutral wire is then reduced. This disparity between the two is known as Residual Current. On spotting a Residual Current, the RCCB is triggered for tripping off the circuit.

A test circuit involved with the residual current device confirms the reliability of RCCB. It also checks whether it has been tested or not. When the test button is pressed/pushed, the current starts flowing. As it creates an imbalance on the neutral coil, the RCCB further trips. Hence, the supply gets disconnected. Thus, checking RCCB’s reliability.


The RCCBs are designed in such a way that, they are capable to sense and compare the difference. Any small change in the current value would trigger the RCCB (to trip off the circuit). Thus, we can say that RCCBs sense the difference between current values in phase and neutral and breaks the circuit in case of an imbalance. Hence provides complete electrical protection.

In an RCCB, the ON and OFF Positions are visible with the help of window provided at the top of housing or the chamber. The ‘Green’ colour indicates ‘OFF’, while the ‘Red’ colour indicates ‘ON’ position.

With advanced technology, some manufacturers have come out with protection for short circuit. The device is also called as RCBO. In such a situation, MCB is not required.

Benefits Of RCCB

• Provides protection against earth fault
• Provides protection against any leakage current
• Automatically disconnects the circuit when the rated sensitivity is outstripped
• Offers possibility of dual termination both for cable and busbar connections
• Offers protection against voltage fluctuation.
• Guards against transient voltage levels.

Sensitivity of RCCB

A human being can sustain an electric shock to the extent of 30 mA. While up to 10 mA may evoke a prickling sensation, 10 mA onwards may lead to muscular contraction. Also, further leading to a respiratory paralysis at around 30mA. RCCBs thus designed to look for small changes in residual current. In cases where protection from fire is required, RCCBs are used to track higher changes in residual current (up to 300mA).

Ultimate Protection Of People and Equipment

The Residual Current Circuit breaker are the safest device for detecting and tripping. Thus, ensuring protection against electric shock. Also, caused by indirect contacts. These devices should be used in series along with an MCB or fuse. It protects them from the damaging thermal and dynamic stresses of any over currents.

Main benefits

• Safety performances ensured worldwide by international marks approval
• High quality execution and attention to details
• Complete range of products and related accessories

Limitations of RCCB

Along with the advantages that RCCB holds, it has some limitations as well:

• RCCB does not guarantee to operate if no waveforms are generated by the loads. It’s because RCCB is designed to operate on normal supply waveforms.
• In RCCB, there might be some unwanted tripping. It’s because whenever there are sudden changes in electrical load, there can be small current flow to earth especially in old appliance.
• RCCB does not protect from current overload. It has been designed to protect only when the live current and neutral current are not the same. But an overload in current cannot be detected.
• RCCB does not shield against line-neutral shocks. It is because the current in them is stable. The current gets balanced as both the terminals are carried together.
• RCCB does not protect from the overheating that strike if conductors are not screwed into terminals.

Types of RCCBs

2 Pole RCCB:

It is used in single-phase supply cases. Mostly that involves only a live and neutral wire. It contains two ends. On these, the life and the neutral wires are connected. A Rotary switch is also worn. It is used to switch the RCCB back to ON or OFF positions. A test button helps to test the RCCB functionality.

4 Pole RCCB:

It is used in three-phase supply cases. It involves three phase wires and a neutral wire. It consists of two ends where the three phases and the neutral wire is connected. In construction and operation, it is like 2 Pole RCCB.In both these types of RCCBs, a Rotary switch is used. This helps in switching the RCCB back to ON or OFF positions. A test button is also provided to test the RCCB functionality.

Difference Between MCB and MCCB, ELCB, RCCB

1.MCB-Miniature Circuit Breaker

It is an electro-mechanical device. It guards the circuit against an over-current. It may affect from short circuit, overload or imperfect design. This is a better option to a Fuse since it doesn’t need alternate once an overload is identified. An MCB can simply be rearranged thereby providing better operational protection. It also offers greater handiness without incurring huge operating cost.

2.MCCB-Molded Case Circuit Breaker

The MCCB is used to control electric energy in distribution having short circuit and overload protection. This Circuit Breaker is an electromechanical device. It guards a circuit from short circuit and over current. They offer short circuit and over current protection. The ranges vary from 63 Amps-3000 Amps.

3.ELCB -Earth Leakage Circuit Breaker

The ELCB is used to defend the circuit from the electrical leakage. When one gets an electric shock, this circuit breaker cuts the power off. It provides personal safety and avoids the gear from the circuit against short circuit and over-load.

4.RCCB (Residual Current Circuit Breaker)

This is essential current sensing equipment. It is used to guard a low voltage circuit against the fault. It comprises of a switch device which is used to turn off the circuit whenever a fault occurs. RCCB is aimed at guarding a body against the electrical shocks. This type of circuit breaker is used where there is a sudden shock or fault happening.

Residual Current Sensitivity

RCCB is designed for protection from earth fault and its consequence to human life such as electrical shocks.As per studies, a person can sustain electrical shocks only to the magnitude of 30 mA.

Thus, RCCBs in low voltage protection are also designed such a way that they will trip off the circuit. And even for a small change in the residual current value of up to 30 mA. The response time is usually within 40 mSec, ensuring that the person is always protected.


Higher values of 300 mA are used where protection from fire hazard is required. This is useful in places where the storage of flammable material is done.

Different Ratings oF RCCBs

RCCBs come in different ratings like 30 mA, 100 mA, 300 mA.

For your household need, 32-63A RCCB of 30-100 mA is considered enough. 30 mA is very sensitive, and you may encounter a few tripping without any clear fault.

RCCB is thus important in providing real-time protection for circuits. In industries and high voltage commercial setups, its importance cannot be undermined. There is always the risk of shocks and accidental deaths. Never forget that only with complete protection, electricity is your friend. Short cuts are harmful. Never apply them. Always consult your electrician for electricity-related issues.

In your electrical circuit, RCCB is an essential protective device. A correctly set RCCB will ensure that there is no fatal injury that can be caused to human being.