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Discuss 3 phase distribution in the Industrial Electrician Talk area at ElectriciansForums.co.uk.

  1. Leesparkykent

    Leesparkykent Staff Member Trusted Advisor

    Yeah I agree that things become a little more tricky when mixing OCPD types.

    60269-1 is the international standard for Low-voltage fuses - General requirements and 60269-2 is the international standard for Low-voltage fuses - Supplementary requirements for fuses for use by unskilled persons.


    The OP says the new board is for small power and lighting. Looking through various charts and comparing the total operating I2t of a 32A B type MCB and pre-arching I2t of the 63A fuse he should be good up to a maximum fault current value for which full discrimination is ensured of around 2.4KA. If the Zdb at the new board was lower than 0.10 ohms he might have a problem.
    Last edited: Jan 7, 2017
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  3. darkwood

    darkwood Dreams in which I'm dying are the best I ever had. Staff Member

    West Yorkshire
    They are for bs88 fuses hence my original query these standards don't apply to mcb's and rcd's which is what we use commonly... ill try find the discriminating charts for mcbs.
  4. Leesparkykent

    Leesparkykent Staff Member Trusted Advisor

    Yeah but the fuses in the head will more than likely be 1361's now BS88 and the fuse in the switch fuse will be BS88 which will provide discrimination if 100A up stream and 63A down stream. A 32A b type 60898/61009 will partially discriminate with the 63A BS88 but full discrimination can be achieved if Zs/Zdb isn't any lower than .10 ohms.
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