determining MCB rating for home circuit


Joined Jun 15, 2011
Are you asking what current rating of circuit breaker should be installed in your mains distribution board (breaker box) for a particular circuit? This would depend primarily on (a) the rating of the installed circuit wiring and (b) your local electrical standards and codes.

In the U.S.:

15 amps breaker requires 14 AWG wire or larger.
20 amps breaker requires 12 AWG wire or larger.
30 amps breaker requires 10 AWG wire or larger.

But IANALE. (I am not a licensed electrician.) And this may vary by your local standards.


Joined Jun 15, 2011
Oh, I see this is in homework help forum. If this is homework, you had better understand why you give the answer you provide. Think about what the purpose of the breaker is. What is it protecting? The device being powered? The circuit wiring in the building? The mains supply wires coming into the house from the power company?


Joined Dec 26, 2010
How to determine what rating MCB required for home electrical circuit.
For many English-speaking members of this forum, "homework" means assignments set by teachers, for students to do out of class time. If you are a student with such a problem, that's OK, but you need to tell us what you have done to solve the problem, and exactly what the difficulty is - we are not allowed just to do your work for you.

If on the other hand, this is a home improvement or maintenance project, it should really be in the "Projects" section.
A detailed answer to your question would require more information - such as what appliances are to be supplied, but really must be in line with local wiring requirements in your region. For instance, no opinion expressed on this forum will cut any ice with any insurance company or building inspector if it does not conform with the relevant regulations.

As the last poster has mentioned, the starting point must be to decide exactly what is being protected. A "home electrical circuit" could be a few amps' worth of lighting in a small flat, or the entire circuit of an electrically heated mansion. Some countries have 110V mains, others 230V, so the size of that breaker is anyone's guess.