What are MCB, Isolators and RCCB and What’s the difference between them?

Many people use MCB rather than using RCCB because in earlier times, MCB was the only option which was available. Thus, many people rely on it rather than RCCB. In the case of RCCB, the fault zone of the electrical circuit can be easily identified. When there is a fault in the circuit, the MCB trips off. On the other side, MCB is very simple to resume again to support the supply. Well, in this article, we will be telling you the difference between MCB, isolator, and RCCB. Here, have a look!

MCB (Miniature Circuit Breaker)

As we all know that, all fuses need to be replaced with the MCB for safety and control purposes. MCBs are electro-mechanical devices which are used to protect an electrical circuit from an over-current. It can be re-closed without any hand-operated restoration.

MCB is used as an option to the fuse switch in most of the circuits. Unlike a fuse, MCB does not have to be replaced every time after a failure as it can be reused.

Another huge advantage of MCBs is that the detection of a problem is easy. Whenever there is a fault in the circuit, the switch comes down automatically and we are hereby informed that there was a fault. We can then manually go and put the MCB back up and the electricity will start flowing again.


1) Rates current, not more than 100 Amp.

2) Trip characteristics are normally not adjustable.

3) Thermal or thermal-magnetic operation.

RCCB (Residual Current Circuit Breaker)

RCCB (Residual current circuit breaker) or RCD (Residual-current device) are aimed to protect people from the risk of electrocution and fire that are generally caused due to the faulty wiring. An RCCB is also very useful when a sudden earth fault occurs in the circuit.

RCCB is basically an electric wiring that trips or disconnects when imbalance or mismatch in electric current is detected. The best part about RCCB is that it does not take much time to take the control over the imbalanced electric current; RCCB takes only about 20 milliseconds to trip.

RCCB is essentially a current sensing equipment that is used to control the low voltage circuit from the fault. It comprises a switch device which is used to turn off the circuit when there is a fault.

Why is it necessary?

There are two types of electrical faults which are very dangerous. One is when there is a high current fault due to some short circuit current, which can be protected by an MCB. Second is when earth leakage arises due to wet hands touched by someone. And an MCB cannot detect this fault, whereas it can be detected by the RCCB. The main principle behind the function of the RCCB is when current is flowing through the appliances it may return in full. There is the difference of milliampere and it may detect and trip the power supply in the circuit. When the current flows out from the appliances, then it is known as residual current. The RCCB is designed in such a way so that the difference can be compared between residual current values between the live and the neutral wires. If there is a small change between the current value of an account, it will trigger the RCCB to trip the circuit. Now it can be said that RCCBs sense the difference between the current value in phase and neutral and can break the circuit.

In the RCCB circuit breaker, the ON and OFF buttons are clearly visible with the help of a window provided at the top of the housing. With the use of advanced technology, some of the manufacturers have come out with the entire protection for the short circuit as well as for the earth fault, this device is also known as the RCBO. In such a situation, the MCB is not required.


A Double pole Isolator

Circuit breaker always trips the circuit but when there is an open contact of the breaker, it cannot be physically seen from outside of the breaker and that is why it is considered as the “not to touch” area of the electrical circuit. Thus, the isolators are created for the safety so that, one can see the condition of the section of the circuit before touching it. The isolator is a switch which isolates the part of the circuit system when it is required. Electrical isolators are the separate part of the system that is created for the safe maintenance. Isolators are generally used at the end of the breaker to repair or to replace.

The main difference between MCB, RCCB, and Isolators

Isolators are generally used in power system while on the other hand, MCB is the circuit breaker. Isolators are manually-operated device, and on the contrary, the circuit breaker is the automatically-operated device. Isolators cut the portion of the substance when a fault occurs. The other devices like MCB and RCCB operate without any interruption. The circuit breaker is the device of an Automatic circuit breaker or Miniature circuit breaker which trips the entire system and if any fault occurs, MCB is to protect the wires from the damage. Whereas, on the other hand, residual current device protects the life-threatening problems. RCCB detects the leakage current and protects from the electric shock.

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