The Differences Between Molded-Case Breakers and Insulated Types

Basics

• Understanding the difference between a molded-case circuit breaker and other types of insulated circuit breakers requires some understanding of how circuit breakers work. A circuit breaker will automatically open or trip when too much current is goes through the circuit. What the circuit breaker is made of can play a role in determining the interruption rating of the circuit breaker.

Molded Cases

• The case or the housing for the circuit breaker is important because it helps to determine the interruption rating of the breaker. These molded cases are composed of various types of plastics, such as glass polymer. Molded cases are rated based on factors such as the physical size of the breaker, the maximum voltage it can withstand, its interruption rating and its ampere rating.

Fusible Switches

• Insulated fusible switches differ from molded-case circuit breakers in that they provide you with more of an "all or nothing" approach to dealing with over-current. The insulated switch fuse will trip once and only once, then it must be replaced. The technology is such that it does not automatically adapt itself to the level of current as the molded case breaker does. Instead, it reaches its limit and breaks, causing it to stop working until the fuse has been replaced.

Advantages

• The advantage to the molded-case circuit design is that it provides you with a degree of reliability that you may not get with an insulated fuse. This makes the molded case circuit design a safer bet. Because you can reset a breaker instead of replace it, there's much less downtime of electrical systems.