Ask a Tradesman
Is it true that if you have a 40 amp 60898 breaker feeding a single phase D.B. that the 61009 circuit breakers in the D.B. that none of the breakers can be over 20 amp ?
No its untrue! Provided the main circuit breaker (40amp BSEN60898 in this case) is correctly selected to provide overload and fault protection for the type and size of cable feeding the distribution board, then its possible to fit 32amp BSEN60898 MCB's or 32amp BSEN61009 Residual Current Circuit Breakers within the distribution board itself for final circuits and remain compliant with BS7671:2008 wiring regulations.
This said, if you have a number of high amperage circuits being fed from the distribution board then even allowing for some diversity, a 40amp supply is quite a poor design! Ideally it would be better to upgrade the supply cable to 16mm/25mm and fit an 80amp or 100amp BS1361 cartridge fuse. Although without knowing what cable size you have installed already it maybe possible to upgrade the MCB to a 45, 50 or even a 63amp if the current carrying capacity of the cable will allow it.
Answered 10th Apr 2013