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Posted By Topic: MCB discrimination

broadsword
Sep 07 2019 14:11

Can anyone steer me to somewhere other than 3000: 2.5.7.2.3 (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...
   

AlecK
Sep 07 2019 17:27

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.
   

broadsword
Sep 07 2019 17:55

cheers Alec... appreciate the rapid response :)
   

broadsword
Sep 07 2019 18:01

so do two 'shalls' and one 'should' make a 'should' or a 'shall' ;) ?