Your home consists of two possible electrical services, depending on when it was built. 1. 120v two wire system, 2. 120/240v three wire system. You can easily determine the type of system by simply looking at the wires coming into your home. You will either have two or three wires. Most new homes today have three wire systems, but a great deal of older homes still have two wire service. If your home still has a fuse box instead of a breaker panel, you can almost bet you have a two wire system. The difference between the two types is simple. Two wire systems have (1) "HOT" and (1) "Neutral" wire. Three wire systems have (2) "HOT" wires and (1) "Neutral" wire. So if one "HOT" wire delivers 120v to the house, logic would state that two "HOT" wires can deliver 240v. See, now that's not so hard....right?
Overload Protection
These devices are your best friends when it comes to the electricity in your home. We're speaking offuses and circuit breakers of course... You know how you've been told not to overload an outlet, but yet you still have six surge protectors strung together with who knows how many things plugged into them? Fuses and circuit breakers are the watchmen of the current. When you demand too much from a outlet, one of two things can happen. 1. You "trip" the breaker, or blow a fuse. or 2. That wire that is only meant to carry 15 amps of current has now gotten so hot it has melted the plastic insulation jacket off, and the wires are touching. What's that smell you ask? Oh, never mind, it's just your house burning to the ground.... Perhaps that scenario is a bit drastic...but we want you to understand the importance of overload protection devices.
A "standard" single pole breaker
A GFCI Breaker. Notice the white "TEST" button, much like what you will find on a GFCI wall outlet. GFCI circuit breakers are designed to protect against ground faults of 6 mA or more.
Arc-Fault Breakers are the newest style of breaker to be developed. They work on a different principle than the other two styles of breakers. The arc fault circuit breaker continuously monitors the shape of the sine wave of the electricity passing through the AFCI breaker. If the sine wave is uneven or jagged, it can be an indicator of a sparking condition somewhere down the line.
The AFCI uses a very simple computer chip that constantly checks for a sparking condition between the hot wire and the neutral wire. It also checks for a high resistance or over-heating condition in either the out-going hot wire or the returning neutral wire. Generally it checks for any sputtering, sparking or overheating condition that might indicate a loose or overheating connection.
Fuses
Many people with older homes have fuses. These work on the same principle as standard breakers in that they "pop" when an overload occurs. However, when this happens, you can't simply flip a switch on fuses; they must be replaced. Replacing them is no harder than changing a light bulb, if you follow the rules...... NEVER use a bigger fuse than what is supposed to be installed. If you are unsure, call a electrician. If a 15 amp fuse blows, do NOT just throw a 20 amp in its place....that's the PERFECT way to start a house fire. Don't do it.
There used to only be one style of fuse, known as a "plug" fuse. These were all the same size and thread pattern; they just had different amp ratings. It was easy to get confused and replace a fuse with one having a different amp rating. And many people did. As a result, many people lost their homes to fires. To combat this problem, Type S Fuses were released. These fuses had a special base that threaded into the fuse box. Each base was designed for a specific size fuse; you couldn't mix and match the sizes. A 15 amp fuse would only fit a 15 amp socket. No more overloading the fuse panel.
The original Plug Style Fuse.
Type S style plug fuse. Notice the different base threads.
Outlets
Believe it or not, there is a reason that one slot on your wall outlet is bigger than the other. The wide slot is for the neutral and the narrow slot is for the hot.
There are certain outlets for certain jobs. They are not all created equal.
1. A "standard" 15 amp outlet.
You can tell it's a 15 amp plug by the missing short horizontal slot.
2. A 20amp outlet looks very similar to a 15 amp, except it has the extra slot.
3. GFCI outlets are required on all new homes built today. Not every outlet must be a GFCI, but they must be placed throughout garages, bathrooms, outdoors, etc. You may recognize them as the outlets with the button on them. Have you ever figured out what that buttonis? It's simple really. It's a Ground-Fault Circuit Interrupter (GFCI), and it's there to protect people from electrical shock. A GFCI monitors the amount of current flowing from hot to neutral. If there is any imbalance, it trips the circuit. It is able to sense a mismatch as small as 4 or 5 milliamps, and it can react as quickly as one-thirtieth of a second.
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