According to, Health Electrical Services, 2022; every year, 1.2 million people globally suffer injuries from electrical accidents1. So, safety is the most important factor in electrical installations. Two vital components that are essential to maintaining user safety and securing electrical circuits are Miniature Circuit Breakers (MCBs) and Residual Current Circuit Breakers (RCCBs). Both provide a level of safety that is necessary for reliability and security, but they also both have pros and cons of their own. In this article we will discuss MCB and RCCB differences and provide advice on when to use either for you.

MCB and MCCB diagram
MCB and MCCB diagram

Miniature Circuit Breaker (MCB)

MCB (Miniature Circuit Breaker) is an electromagnetic device that contains the whole compound in a molded insulating material. MCBs are automated switches used to protect against overcurrents in electrical circuits. This indicates clearly that an MCB connected to a circuit will break the connected circuit if an excess current flow condition occurs through the MCB over the designated value. They serve as the first line of defence, lowering the danger of fire and preventing damage to equipment by tripping and disconnecting the circuit when an excessive current is observed. The maximum current that the MCB is capable of accepting before tripping is indicated by the ampere rating. The current rating in standard MCB circuits ranges from 2 Amp to 125 Amp 2.

Working principle of MCB
Working principle of MCB

Residual Current Circuit Breaker (RCCB)

RCCBs (Residual Current Circuit Breakers), often referred to as ground faults or residual currents, are specialist devices made to protect against the risk of electric shock hazards Protecting the electrical circuit or equipment from two major electrical failures is the primary purpose of an MCCB: 1. Overcurrent fault 2. Short Circuit Fault3. The function of MCCB is almost that of MCB.  The only difference is that MCCB is made for high to extremely high currents. The majority of MCCB applications include high current in sectors such as motor circuits, LT Panel incoming breaker applications, CNC machines, elevators, electric cranes, etc. The range of rated current is up to 1000 amperes 2.

Structure of RCCB
Structure of RCCB

Key Functions of RCCB

  • Electric Shock Protection: The primary and critical purpose of an RCCB is to protect people from the risk of electric shock. It measures the current passing through the live and neutral wires. It instantly disconnects the circuit if it detects a significant imbalance or residual current, which might suggest current leakage to the ground.
  • Residual Current Detection: RCCBs continually monitor the current flowing in the live and neutral conductors. The current in these conductors should be equal in a fully operating circuit. However, if a fault occurs (for example, a human comes into touch with a live conductor), some current may leak into the earth. When the RCCB senses an imbalance, it trips the circuit.
  • Tripping Mechanism: When a residual current is detected, RCCBs use an electromagnetic tripping mechanism to quickly disconnect the circuit. Tripping times are often very short, enabling rapid response to dangerous electric shock situations.
  • Sensitivity Variability: RCCBs have various sensitivity ratings, which are often referred to as Type AC and Type A. Type AC detects just alternating currents, whereas Type A detects both alternating and pulsing direct currents. This adaptability provides adjusting for individual applications and environments.
  • Preventing Fires: In addition to protecting against electric shock, RCCB Installation help to prevent electrical fires. The immediate disconnect of a damaged circuit decreases the danger of overheating and fire caused by electrical problems.
  • Safety Standards Compliant: RCCBs are designed and manufactured to meet specified safety standards (such as IEC/EN standards). This ensures that they fulfill the necessary performance and safety requirements for securing electrical installations and people.

Types of RCCB

There are multiple RCCB in Electrical Circuits varieties on the market right now. The kind of circuit or power system determines the different design characteristics and application-specific capabilities available for these. These typically comprise single and 4-pole RCCB kinds and RCCB types determined by the features of the tripping curve (A, AC, F, or B). RCCB types are determined by pole numbers (single and 4-pole) and types of RCCB by tripping curve characteristics (A, AC, F, or B) 4.

  1. Single pole RCCB: Particularly designed for single-phase systems. Single pole or single phase RCCBs are generally used in residential and small commercial applications due to low voltage systems.
  2. 4-pole RCCB: The 4-pole RCCB is designed for higher voltage three-phase systems. It has one output (neutral wire) and three inputs (live wires). As this kind of equipment can better manage higher current flows, it is commonly used in industrial settings.
  3. Type AC RCCB: This type of RCCB is conventional and designed for use with sinusoidal AC circuits. It is unable to accurately identify smooth or pulsed DC current problems. It will also not work with circuits that use different frequencies than the standard 50/60Hz 4.
  4. Type A RCCB: You can consider the type A RCCB to be an upgraded version of the AC type. It can detect pulsed DC current faults in addition to AC current faults from sinusoidal circuits. Because of this, it can be used with any kind of appliance.
In a PV system, using type A RCCB
In a PV system, using type A RCCB

When to Use MCB and RCCB?

Use MCBs when:

  • Protecting against overloads and short circuits is the primary concern.
  • There is a need to protect electrical equipment from excessive current flow.

Use RCCBs when:

  • Protecting against electric shock hazards is the primary concern.
  • There is a risk of leakage currents due to moisture or faulty insulation.
  • There are electronic devices in the circuit, which may produce pulsating DC currents.

Electrical safety is an essential concern for both MCBs and RCCBs, as they each solve different issues. A safe and dependable electrical installation requires an understanding of these distinctions and when to apply them. An electrical distribution system can be fully protected against overcurrents and electric shock risks by including both MCBs and RCCBs.

The following table provides an overview and detailed comparison between MCB and RCCB:

Feature MCB RCCB
Main Function Protects against overcurrents Protects against earth leakage currents.
Mechanism of Tripping Magnetic and thermal tripping Electromagnetic tripping for earth faults
Trip Characteristics Faster than average tripping time Shorter trip time to avoid false trips
Type of Protection Protection against overcurrent Protection against earth faults (residual currents)
Sensitivity Sensitive to overcurrents Sensitive to minimal leakage currents
General Use Electrical circuit protection Protection from electric shock
Tripping Test Button Present Present
Site of Installation Distribution boards and electrical panels Near the power source or in distribution boards
Neutral Connection No neutral connection is necessary. For proper operation, a neutral connection is required.
Commonly Used Ratings Normally up to 125A Up to 100A (higher ratings for particular applications).
Polarity Sensitivity It is not polarity sensitive. Sensitive to current flow direction
Applications Residential, commercial, and industrial Residential, commercial, and industrial

Both MCBs and RCCBs play vital roles in electrical safety, and the best choice is determined by the specific needs of the electrical system. In many circumstances, a combination of MCBs and RCCBs, or an integrated RCBO, can provide the most comprehensive protection. It is important to follow electrical rules and standards and to consult with specialists for unique applications.


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