What is an MCB and how does it work?

What is MCB

A Miniature Circuit Breaker is an electromechanical device designed to protect an electric circuit from over-current – A term to describe an electrical fault caused by either overload or short circuit. 

Where it is Used

Typical Uses for Domestic MCBs
Whilst every installation is different and should always be designed by the fully qualified professional electrician on site, there are some standards which most domestic wiring schemes adhere to:

6 Amp – standard lighting circuits

10 Amp – large lighting circuits – though these are becoming rarer in domestic settings as technology and trends move towards lower energy lighting sources such as LED.

16 Amp and 20 Amp – Depending on the power rating these are both commonly used for immersion heaters and boilers

32 Amp – Ring Final. The technical term for your power circuit or sockets. A two bedroom house for example may have 2 x 32A power circuits to separate upstairs and downstairs sockets. Larger dwellings can have any number of 32 A circuits.

40 Amp – Cookers / electric hobs / small showers

50 Amp – 10kw Electric showers / Hot tubs.

How an MCB Works:

1. Latch
2. Solenoid
3. Switch
4. Plunger
5. Incoming Terminal
6. Arc Chutes Holder
7. Arc Chutes
8. Dynamic Contact
9. Fixed Contact
10. Din Rail Holder
11. Outgoing Terminal
12. Bi-metallic Strip Carrier
13. Bi-metallic Strip