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Is it safe to replace B10 MCB with C10?

Discussion in 'Power Electronics' started by patkim, Oct 7, 2019.

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  1. patkim


    Dec 7, 2017
    As the title suggests, I just wish to know if it's all right to replace a B10 MCB (Miniature Circuit Breaker) with C10.
    I think B & C are curve ratings and related to tripping mechanisms I suppose, the multiplier of the current at which it will trip.

    Also what does the number 6000 stand for on the MCB?
    Can 6000 be replaced with 10000?

    The operational info is B10 240/415V 6000. The load on this MCB is just typical 230V 5A devices like household ceiling fan, tubelight, LCD TV and a desktop PC.

    In my house all Single Pole MCBs are B type. The master Double Pole is B40 10000A
    Thanks and regards.
  2. 156MHZ


    Oct 7, 2019
    Hi, a C curve mcb has a slightly longer tripping time than B curve. They are normally used on inductive loads such as motors and transformers because of the initial inrush or start up current. I would not install a C curve mcb unless you are getting repeated tripping when a device is started. Not sure about the 6000a & 10000a. I think it relates to what the mcb will withstand if a major fault occurred. My advice is always run it past a qualified electrician.

  3. patkim


    Dec 7, 2017
    Thanks for the reply. So will a slightly longer tripping time cause any issues or possible damage to the device being protected? Device list is as mentioned in the earlier post. It seems yes, as you said that number in thousands appears to be the max fault current the MCB can sustain.

    After more Googling I found one article here It does explain details about various parameters printed on MCB.
  4. Bluejets


    Oct 5, 2014
    The 6 and 10 are indeed the KA rating of the breaker.
    In many instances it is desirable to have a higher KA rating breaker installed.
    In Aus, 3KA breakers were the standard for many years but now it is 6KA.

    No idea what country you are from but in many with MEN system, double pole on the main isolator switching the neutral is illegal. You may of course have 2 phase supply which negates this comment.

    As to why you would want to replace a B curve breaker with a C curve is a bit of a mystery.
    To begin with they are, as far as domestic installations and many commercial, not the norm, simply not required.
    Cost is probably many times greater as well.
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