The maximum ZS for a type B 6 amp mcb to BS EN 60898 is listed as 5.87 ohms by my calculations (and NICEIC , iCertify) this is incorrect.
6 x 5 (from 3-5 current trip) = 30 , 230/30= 7.666666 (I believe this is correct with BS7671 brown book , 7.66666 x 0.95 (cMin)=7.283333 x 80% (conductor temperature adjustment) = 5.826666
therefore 5.82 should not be exceeded .