Because a majority of loads connected to MCCB are of an industrial type which usually have a higher current rating and in case if a short circuit occurs, then SC current will be in the range of 50/100kA (always depends upon impedance value of the connected load).
MCCB react more quickly compare to MCB in the case of overload & short circuit fault condition. Also, MCCB has one more advantage over MCB which is Trip Setting Adjustment (overload current threshold limit can be adjusted depending upon connected load). Our normal MCB’s are not designed to handle such higher short circuit current and also do not have a provision of trip setting adjustment. Hence we prefer MCCB’s when a current rating is higher.
MCCB’s available in market ranges from 10 to 1800/2500 Amp with short circuit rating from 10,000 – 200,000 (200kA) Amp. Whereas MCB range starts from 2 Amp and ends with 100/125 Amp with Max. SC current rating available is 18,000 Amp.
MCB’s are designed to handle the household load. Also, MCCB’s prices are always on higher side compare to MCB of same current rating. Hence we use MCB’s for household and MCCB’s for industrial purpose.