What is an MCB?

Last Update Date : Mar 27. 2018



A circuit breaker (popularly known as CB) is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow.


Difference between a circuit breaker and a fuse?

Unlike Fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.


What is a MCB(Miniature circuit breaker)?

MCB's are low voltage circuit breakers with the rated current not more than 100 A. They are most common in domestic operations.


Why does MCB trips?


● Breakers are a safety device. It is designed to protect not only the equipment but the wiring and the house as well. So when it trips, there is a reason and it should be taken seriously.


● One very common cause for breakers to trip are loose electrical connections and can easily be corrected by tightening them. Try one time to reset it by turning it to the “off” position and then back to the “on” position. Do not just keep resetting it and try to ignore the situation. It is trying to tell you something.


● If it is a result of a thunderstorm, always remember that you are dealing with high voltage, high amperage and possibly high temperatures which can cause serious damage to life and property. Note that breakers should not feel hot to the touch. If it is hot, it indicates a problem and not to be ignored.


● If when you reset it, it immediately trips, that is usually indicative of a direct short. Do not even try to reset the breaker again.


● Sometimes the breaker for the outside unit trips because the compressor is having a hard time starting and will require a “hard start” kit to get it going again or it may be as simple as replacing a defective capacitor.


Items in blue can be addressed or fixed by the homeowner. Those in red usually require a service call.

Severe thunderstorm

Low voltage to the house as in a brown-out
Weak compressor

Under-sized breaker or wire

Defective breaker

Loose breaker

Loose electrical connection

Weak capacitor

Locked up motor or compressor 

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