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Circuit Breakers & Residential Electric Wiring

Circuit Breakers

Circuit breakers are so common today that many people take them for granted. They are the silent guardians of our household electrical systems. Without circuit breakers, the possibility of electrical fires would dramatically increase.

Prior to the advent of circuit breakers, fuses were used to protect the wiring in houses. Many people fail to realize that the wiring which originates in the fuse or circuit panel and terminates at each receptacle, switch, or fixture must be protected. Fuses and circuit breakers serve this purpose.

Short Circuits & Fire

The wiring which allows us so many conveniences has to be insulated. This insulation not only prevents you from being electrocuted, but also prevents wires from short circuiting. Short circuits occur when a wire energized by single phase 120 volt current touches a ground or neutral wire without the benefit of resistance.

When a wire short circuits, the electricity flows extremely rapidly through the wire. It's not much different than you pushing the accelerator in your car to the floor. Things can rapidly go out of control. This rapid flow of electricity creates friction which in turn creates heat. The heat can quickly melt the insulation covering the wire.

This heat can easily start a fire. Also, short circuits often create sparks. The heat is incredible. In fact, anyone who has witnessed a welder using an arc welder has seen a continuous short circuit. The short circuit is somewhat controlled in that the welding rod is used to 'control' the direction and flow of the electricity.

Resistance = 'Yellow Light'

We all know that electricity flows through wires, because we have to pay for it. However, what is different about this flow of electricity as opposed to the flow during a short circuit?

The difference is speed. When electricity encounters an electrical motor, a light bulb, an oven or toaster heating element, it has a tough time getting through those materials. In other words, it slows down. The heat or energy that otherwise would have arc welded is now being put to work for good purposes. That's it in a nutshell.

Wire Capacity

Electric wires are available in different sizes. They are sized according to their thickness. This is often referred to in the industry as its 'gauge.' Common household wiring is usually 14 and sometimes 12 gauge.

The numbering system used for these gauges is somewhat confusing. As the gauge number gets higher, the wire gets thinner. Thinner wires cannot carry as much current (electricity) safely as a thicker wire.

Electric wires carry electricity much like pipes carry water. You can only force so much water through a certain sized pipe. The same is true with electricity. Wires are rated as to the amount of electricity they can safely carry or transmit. The rating is a measurement of the electrical current or amperes (amps).

It just so happens that circuit breakers are rated the same way! That is so you can match the wire size in a particular circuit to the proper sized circuit breaker.

What's a watt?

Homeowners usually are familiar with two measurements of electricity: volts and watts. For example, virtually everyone knows that the voltage of the electricity in their house is 120 and 240 volts.

People also deal in watts on a daily basis. That's how you buy light bulbs. 75, 100, 150 watt bulbs are very common. Electrical appliances are often sold based on their wattage. Electric hairdryers are often 1,200 watts.


Very few homeowners I have dealt with, however, know how to relate all of these numbers. It is extremely easy. It is also very helpful, as you quickly begin to understand why a circuit breaker pops or a fuse blows.

The conversion formula is simply this: Watts = Amps x Volts. So, in numeric form, 1,800 watts = 15 amps x 120 volts. Is it beginning to get less fuzzy?

Your bathroom breaker pops if you try to operate your hairdryer, mirror lights, and curling iron all at the same time. Too many watts at one time are trying to get past the breaker! Watch those watts!

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