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MCB vs Isolator - Know The Difference!

If you are looking to add circuit breakers to your home, you have probably encountered these two breakers; Miniature Circuit Breaker (MCB) and Isolator.

The main purpose of miniature circuit breakers is to protect against erratic current flow. While an isolator is used to isolate the part of the electrical system that is mainly needed for maintenance work.

Here I will explain the difference between them, with examples for each type of device.

Miniature Circuit Breaker (MCB)

These circuit breakers perform the vital role of breaking the circuit to prevent damage from the excessive current due to a short circuit or overload.

When a short circuit occurs, a large amount of current begins to flow causing the MCB to trip almost immediately. In the event of an overload, it takes a few seconds to trip and interrupt the circuit.

It generally has a built-in mid-trip function that indicates whether the MCB is switched-off or tripped due to a circuit fault. This makes it easy to recognize a circuit fault as the knob stays in the center in case of overloading or short circuit

Overloading and short circuits in the power supply can be dangerous for both people and equipment. To minimize these risks, MCBs are installed.

Residual Current Circuit Breaker (RCCB)

It is a manually-operated device used to isolate / break the circuit with the power supply. They serve as the perfect companion to ensure complete de-energization of the electrical circuits in residential buildings and business premises.

They are typically used to interrupt the power supply for repair and maintenance work. Visually they look very similar to an MCB, but technically they are different. MCB is an automatically-operated circuit breaker for overload and short circuit protection, while an Isolator is a manually-operated device for simply breaking off the circuit.

They are usually connected to the main power supply to break the circuit when needed. If an MCB is connected instead, it will trip even if one of the MCBs in the circuit trips. An isolator ensures that the power supply is not interrupted due to a malfunction in a certain part of the circuit.

They operate under off-load conditions when the circuit is not drawing any appreciable current from the power source. They are used to isolate part of or complete the circuit with the power source to perform maintenance work. It ensures that no current flows on the load side, even if impulse voltage appears in the circuit.

The main difference between the two is that an MCB is used to prevent short circuits & overload protection and an isolator isolates a certain part of the electrical circuit when needed.


Basic Difference

MCB

Isolator

Cost

More

Less

Manual ON/OFF

Yes

Yes

Overload Protection

Yes

No

Short Circuit Protection

Yes

No

Sensitivity

Relatively Less

N.A

No. Of Poles Available

1,2,3,4

2,3,4

Application

Fuse Alternative, Protective Circuit, Local Control Switch

Aid Maintenance Work, Main Power Switch

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