Imported: MCB discrimination

This includes types of overcurrent, Short Circuit and RCD protection
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Imported: MCB discrimination

Post by DougP »

Sep 07 2019 14:11

[shim]Can anyone steer me to somewhere other than 3000: (a) (iii) with respect to selection of MCBs to provide required discrimination please?

for some reason i had in my head that a gap of one size was permitted... so a 32A submain could have a 20A mcb in the DB but think i might be wrong...

Sep 07 2019 17:27

[shim]Why would you look anywhere else than the clause that covers it?

Noting that 2018 edition changes this rule to 1.5 x instead of 2x; and that it's only a "should" in any case.

so as a rule-of-thumb; 2 standard rating steps assuming both are same trip curve.

Sep 07 2019 17:55

[shim]cheers Alec... appreciate the rapid response 🙂

Sep 07 2019 18:01

[shim]so do two 'shalls' and one 'should' make a 'should' or a 'shall' 😉 ?
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