The main difference between molded case circuit breakers and low-voltage power circuit breakers are that the power breaker is built to withstand heavy short circuit current on delayed opening. The power breaker contacts must remain closed under the electromagnetic short circuit forces, this is why it is built heavier and larger than molded case breakers of equivalent ampere rating. The low-voltage power circuit breaker can be readily inspected and some damaged or worn parts may be replaced during its life (depending on the manufacturer's recommendations). On the other hand, most molded case breakers are permanently sealed. They are designed for a set life without adjustment or parts replacement.
LVPCB are frequently used as main breakers and on large feeders where selectivity would be difficult without the flexible controls they provide (especially the use of delays). Newer versions of the molded case breaker have microcomputer chips and electronic trip schemes may also be appropriate. However, the simpler molded case devices would probably still be used for smaller circuits due to cost. Fused switches are also widely used.
