B type MCBs operate at an overload of 3 to 5 times the rated current. Type B MCBs are usually used in domestic installations where the inrush currents and surges are low.
C type MCBs operate at an overload of 5 to 10 times the rated current. These MCBs are used in commercial and industrial installations where high inrush current are likely due to motor starting or due to large no of fluorescent lighting.
D type MCBs are used in special applications such as x-ray machines and transformers which can draw heavy inrush current.