What Is a Molded Case Circuit Breaker?


If your home has been constructed or remolded in the past 25 years, you're probably familiar with the molded case circuit breaker. These all-in-one components sit neatly inside the main electrical panel of your home and business and perform their service quietly, only to make themselves known when they have performed the task of over-current protection.


  • Replacing glass and long cylindrical fuses, molded case circuit breakers have brought cost savings and reliability with their introduction. At one point in time, if a fuse blew, they would have to be replaced in order for the electrical power to be reinstated to a particular circuit. Many times though, the fuse may blow again as the problem may have not been corrected. A molded case circuit breaker, on the other hand, does not have the problem of a one-time usage.


  • Resetting a circuit breaker is much like turning on a light switch. A simple flip and the over-current protection device can be reset and reused hundreds of times. This type of reliability has saved homeowners countless dollars and time from not having to replace a blown fuse.


  • Molded case circuit breakers are manufactured in such a way so the end user will not have access to the internal workings of the over-current protection device. Generally constructed of two pieces of heavy-duty electrically insulated plastic, these two halves are riveted together to form the whole. Inside the plastic shell is a series of thermal elements and a spring-loaded trigger. When the thermal element gets too warm, from an over-current situation, the spring trips, which in turn will shut off the electrical circuit.


  • Large industrial molded case circuit breakers can also have an adjustable range setting included on the face of the device. Generally used for higher amperages, 100 amperes or greater, these main circuit breakers can be adjusted for spikes that may occur in starting certain equipment.


  • Molded circuit breakers can range in size from 15 amperes for the home and up to 3000 amperes for industrial settings and equipment. The larger industrial breakers can also be enclosed in metal cabinets twice the size of a common household refrigerator.

Related Searches


  • National Electrical Code; NFPA; 1988
Promoted By Zergnet


You May Also Like

  • Parts of a Circuit Breaker

    In a perfect world, a building would be wired for electricity, and every time we turned on a switch, the electricity we...

  • Electric Circuit Breaker Types

    Circuit breakers, whatever their type, share a common function---to protect an electrical circuit against overloading and to avert damage to the circuit...

  • What Is the Function of a Circuit Breaker?

    A properly designed electrical system is very safe. However, when problems occur, electricity can generate dangerous heat and can be fatal to...

  • Square D Circuit Breaker Types

    Circuit breakers detect overcurrent and short circuit conditions and shut off electrical flow to prevent damage to electrical circuits. Schneider Electric manufactures...

  • What is a Current Limiting Circuit Breaker?

    All circuit breakers are current limiting inasmuch as they open or "trip," cutting off the current in a circuit, in the event...

  • What Is a Type D Circuit Breaker?

    Circuit breakers are divided into types based on their instantaneous tripping current. This is the minimum current at which the circuit breaker...

  • GE Circuit Breaker Types

    Circuit breakers perform the management, transportation and stopping of electrical currents. Under normal circumstances, the circuit breaker performs all three functions but...

Related Searches

Check It Out

22 DIY Ways to Update Your Home on a Small Budget

Is DIY in your DNA? Become part of our maker community.
Submit Your Work!