Type B MCB:
Type B devices are generally suitable for domestic applications.
They are designed to trip at fault currents of 3 - 5 times rated current.
Type C MCB:
Type C devices are the normal choice for commercial and industrial applications
These devices are designed to trip at 5 - 10 times rated current
Type D MCB:
The Type D devices have more limited applications, normally in industrial use where high inrush currents may be expected.
Type D devices are designed to trip at 10 - 20 times.