Location: Breakers Vs Fuses

Breakers vs fuses

Breakers, and fuses are both designed to limit the current, or amperage through a circuit when it is at an unsafe level. Both breakers and fuses are designed to operate over a fairly tight range of voltages so that they can "SENSE" the amperage flowing through the circuit accurately. However, this is about where the similarities end. Fuses protect electronics, sensitive equipment, because the blow faster than breakers. Breakers are designed to protect wiring circuits, motors, and other more rugged electronics as they blow more slowly. Let us look at the physical characteristics of both breakers and fuses to see why...

What is a Fuse?
Electronics are sensitive, so IC boards like this are best protected by fuses.Fuses are simply a piece of metal that melts when it gets hot. Built inside a non-conductive insulator, a filiment of metal melts at a prescribed temperature, which in turn mathematically corresponds to a certain voltage and amperage. This being said, fuses are simple, they get hot and they melt. Usually the process happens very quickly, protecting pricey electronics behind the fuse.

Pros:
Blows fastest to protect electronics. Available in a wider variety of voltage and amperage increments. Other positive characteristics of fuses include operation in a variety of temperature, environmental, and atmospheric conditions. You can put them nearly anywhere, fuses are pretty resilient, but they detect power surges nearly the same under any circumstance.

Cons:
After it melts it must be replaced with a new fuse. Fuses are usually fantastic for electronics, but not usually as nice for motors which need a spike of power to start. The speed of the fuse (fast blow vs slow blow) can help to avoid costly fuse replacement daily with a motor install, but typically a breaker is best for these applications.

What is a Breaker?
Motors and Wiring Systems are best protected by breakers.Breakers on the other hand are very complicated little mechanical devices. Usually consisting of at least 2 contacts, and a spring loaded contacter. When too much current flows through the breaker, the Bi-Metallic contactor, (aka two types of metal) bends according to the heat. When the contactor bends far enough it separates the connection, allowing the spring to pull and "break" the connection. These are great when you don't want to replace a fuse, but there are limitations to their usage. Typically a breaker will react to the situation more slowly than a fuse. And breakers don't like any vibration or movement. It can lead to funny "breaks".

Lastly, let's not assume that breakers last forever. Breakers can be reset a finite number of times as each break causes a bit of damage. Each time a breaker is tripped or thrown, the circuit must be interrupted. As the circuit is interrupted, a small amount of electrical arcing takes place, which corrodes and damages the contacts at the point of the arc. As the contacts are continually corroded, the operation of the breaker is deteriorated.

Pros:
Best for applications where more loose limits are enforced. No cost to reset the breaker. Best for applications where a motor blows a circuit routinely and should be shut down for duty cycle reasons.

Cons:
Breaks slowly which can allow electronics behind the breaker to sustain damage. (why we use surge supressers on computers). Breakers are susceptable to vibration and shock, causing the breaker to break the connection when no over current situation exists.

FINALLY A WORD OF WARNING TO HELP YOU DECIDE!
Neither fuses nor breakers "limit" the current in a circuit perfectly. A short circuit will cause a flow of power until the breaker or fuse stops the flow. The speed with which the current is arrested defines the damage sustained to the circuit. Heat doesn't take long with power. So the question for you is simple, can you afford to wait on that spring? Your TV, Monitor, and Computer can't wait.

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