Difference Between MCB and RCCB:
MCB is Miniature circuit breaker and RCCB is Residual current circuit breaker. Both are most commonly used device in electrical. Combination of MCB and RCCB are used to protect from electrical shock, overload, short circuit and Earth fault. However, both mcb and rccb has advantages over each other. In this tutorial we are going to see the main difference between miniature circuit breaker (MCB) and residual current circuit breaker.
What is circuit breaker:
Circuit breaker is an automatically operated device to protect an electrical circuit from flow of excessive current or fault condition such as short circuit, overload, Earth fault etc. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.
The Main difference between normal switches and mcb is, they can trip the circuit when the fault detects and to switch on the circuit you have to press upward in mcb the same can be done downward in normal switches.
Difference Between MCB and RCCB:
|Definition||Miniature Circuit Breaker||Residual Current Circuit Breaker|
|Construction||Miniature circuit breaker consists of Body of MCB, Incoming Terminal, Magnetic Coil, Bimetal Strip, Arc Chute, Copper Braid, Operator ON/OFF handle etc.||RCCB consists of CBCT (Core Balanced current Transformer), Magnetic relay coil, incoming and outgoing terminal and tripping mechanism|
|Over load Protection||It used to protect against overload.||No|
|Short Circuit protection||Yes||No|
|Earth Fault Protection||No, It does not protect against earth fault||Yes, It is used to protect the electrical circuit against Earth Fault|
|Cost||Less Cost||high cost|
|Working Principle||Principle of thermal overload protection. when the current flow through the conductor increases, which increases the temperature of the conductor. Due to, increase in temperature of the bimetallic strip get bend, this activate the tripping mechanism. Watch the Video for better understanding||It is working under principle of core balanced current transformer. The phase wire and neutral wire will be passed through the CT. Since the output of the CBCT will be vector sum of the phase and neutral current. Here, The CBCT compares phase current and neutral current. The output of the CBCT will be connected to the relay operating coil. Under Normal condition the current in the phase wire and neutral wire will be equal. Since CT does not produce output. During Earth fault, the leakage current flows through the earth, since phase current will be higher than the neutral current. This unbalance current will be deducted by CBCT. If the output current exceeds the operational threshold, then RCCB isolate the circuit from the fault.|
|Rating||63A Full load current||63A Full load current, 30 to 300 mA Earth leakage current|
|Nuisance tripping||Less||Frequent, Sudden changes in electrical load can cause a small, brief current flow to earth, especially in old appliances. RCDs are very sensitive and operate very quickly; they may well trip when the motor of an old freezer switches off. Some equipment is notoriously `leaky’, that is, generate a small, constant current flow to earth. Some types of computer equipment, and large television sets, are widely reported to cause problems.|
|Protection against Shock||No, MCB does not protect the human against electrical shock||Yes, It is mainly used for protecting the human from electrical shock. The lower range 30mA RCCBs are used. Here 30mA mentions that, the difference between line current and neutral current should not be exceeded more than 30mA.|
|Number of Poles||Single Pole, two pole, three poles and four pole||It does not have single pole option. Only Possible of two pole, three poles and four pole|
|Application||Homes, Commercial, Industrial etc.||Mostly used in Homes|
|Terminal Connection||Bottom terminal Consider as incoming (Line) and Top terminal consider as outgoing terminal (Load)..refer the picture||Top terminal consider as incoming terminal (Line) and Bottom terminal consider as outgoing terminal (Load).see the picture|
|Test Operation||No Test Operation||We can Test the device Working Condition using Test switch|
MCB and RCCB Connection:
Most of the time MCB and RCCB are used jointly in an electric circuit to protect the circuit from short circuit, overload (From MCB) and earth fault (from RCCB). The MCB should connect before RCCB connection. Let see why!
Case 1: MCB is connected before RCCB:
If the short circuit fault occurs on the house load side, then MCB detects the short circuit and trip the circuit. At the same time, Now fault occurred in between MCB and RCCB means, MCB detects the fault and trips the circuit.
Case 2: MCB is connected after RCCB:
Fault on the house load side, MCB detects the fault and trips the circuit. At the same time, if the fault occurred in between RCCB and MCB means the MCB cannot protect the circuit against short circuit and RCCB does not deduct the fault. The fault will be remaining in the line. That’s why MCB should be connected before the RCCB.