Electrical Wiring Basics

electric wire switch box

This article describes how to install basic wiring connections in a home and also has a few safety tips basic electrical wiring knowledge.

brief how to

  1. Safety First
  2. What Wire Colors Mean
  3. Wire Sizes
  4. Wiring Switches, Outlets and Light Fixtures
  5. Wiring Lights

safety

Anytime you work around electricity it is very important that you practice safe procedures. Turn off the power to any circuit you will work on. Use a proximity tester to verify that the circuit you are working on is actually turned off. Make sure the tester is working by testing it on a circuit that you know is on before trusting it.

The best way to turn off a circuit is to switch the circuit breaker to the off position in the electrical service panel that feeds the circuit you are working on.

Always use the same size wires on a circuit; for home circuits it is usually 12 or 14 gauge wire.

The handy boxes in the wall that hold the wire connections for switches, outlets are sized to hold a specific number of wires. Building codes require that the amount of wires in the box are equal to or less than what the box is rated for.

step 1 Wire colors

Wires are color coded. Black or red are hot, White is Neutral, Green is ground. All three should be present for a safe circuit. Older wiring may not have the green ground.

step 2 Wire Sizes

wire size color

Homes are most often wired with 14 gage or 12 gage wire. You can identify the wire gage by reading the size on the wires protective sheath or sticking one of the wires thru a size gage on your wire strippers. The larger the wire the more current it can handle. So the wires to an electric stove are usually 8 or 10 gauge, see the manufactures instructions to know exactly what your appliance needs.

The typical amps per gauge of wire are as follows: (these numbers are basic guidelines and may be over ridden by other factors)

  • 14 gage wire = 15 amp breaker
  • 12 gage wire = 20 amp breaker
  • 10 gage wire = 30 amp breaker
  • 8 gage wire = 40 amp breaker
  • 6 gage wire = 50 amp breaker

All UL listed (Underwriter Laboratories) appliances and equipment will state the amperage required to run it.

Wires get bigger as the size gets smaller and wires get bigger as the power requirement increases.

step 3 Types Of Connections

Connections between wires, outlets and switches are fairly simple. When connections are done right they will give years of service but when they are done wrong it is common for electrical problems, including short circuiting to occur.

connectiong to a switch or outlet:

Using the back stab holes on the back of switches and outlets is not as secure a connection as the screws on the sides, but this topic is always heavily debated. I prefer to always use the screws and wrap the wire in the clock wise direction so it does not back off the screw as the screw tightens.

electric outlets connection

White wires connect to the chrome screws

Black wires connect to the Brass screws

Green Wires connect to the green or black screw on the switch, outlet or handy box when it is available; usually when metal boxes and conduit are used. Otherwise the ground will always connect to the other ground wires in the box, they can be twisted together and fastened with a crimping ring.

Connecting two or more wires together is done with by use of a wire nut. Make sure the wire nut is sized for the size of wire and number of wires you are attaching together. I prefer the brown wire nuts shown here because they take a wide range of wire sizes.

twisted wire cap

step 4 Wiring Switches, Outlets and Light Fixtures

single switch:Wiring a switch is simple when you have one switch controlling the light(s). It is done by attaching the black wire coming from the panel to the bottom screw and the black wire going out to the light to the top screw. Then attach the white wires together. Attach the green wires to each other and run a pig tail to the ground screw on the switch.

switch wiring: two switch.

switch wiring: three switch.

outlet wiring: For a more detailed explanation of wiring an outlet see the article How To Wire An Electrical Outlet. Wiring an outlet is also simple. It is done by attaching the white wire to the chrome screw, the black or red wire to the brass screw and the ground wire to the ground screw.

electrical outlet wiringoutlet black wire

The simplest way to wire an outlet is to have it at the end of a power run. Simply attach the white wire to the chrome screw, the black or red wire to the brass screw and the ground wire to the ground screw.

Wire outlet to next boxWire outlet to next box

If the outlet is one in circuit of outlets you will use the second set of screws on the sides of the outlet to attach the new wire to and continue back out of the box to the next outlet.

2 gang outlet

If there are two outlets in the same box, a double gang, and it is the last outlet in the circuit you will use a 5 inch piece of wire, keeping the colors the same, and "jumper from the first outlet to the second.

If there are two outlets in the same box and you are continuing the power down the wall to another outlet you will come into the box and attach two jumpers that go to each outlet and also attach the wire going to the next outlet on the wall.

Step 5 Light wiring

Attach the white wire coming from the switch to the white wire on the light. Attach the black wire coming from the switch to the black wire on the light. Attach the ground wire to the ground wire or screw on the light.

If you are going to a second light you will attach the wires going out of the light box to the same color of wires.

If the lights have a three way switch things are a little more complicated, see the article Wiring a Three Way Switch.

To see a more detailed example of how to wire switches, outlets and light fixtures follow these links:

  • Wiring a Switch
  • Wiring a Outlet
  • Wiring a Light Fixture

 

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