Learn the basics of home electrical wiring. Electrical wiring can be tricky, especially for beginners. For this reason, it is usually best to hire a professional for anything other than a simple job. Otherwise, you could risk injury, damage, or fire. If you are planning to do a DIY project that has an electrical component, there are some basic things to know about installing wiring.
Understand electrical wiring
Since the 1940s, any home built (or any older home that has been rewired) has had to follow an electrical code – the NEC, written with safety in mind.
The NEC code identifies the types of electrical cables by color.
When removing the plate from a switch, you’ve probably seen yellow, white, black, red, or green wires. They are not there to be decorative; each serves a specific purpose, and some don’t get along with others.
How to connect electrical cables
When installing wiring, it is necessary to identify the parts of the wiring: the non-metallic electrical cable, the outer sheath (the jacket), and the inner wires.
The colored wire you see (green, black, red, blue, or white) is actually the sheathing that covers the inner copper wires.
If you look closely, you will see the markings stamped on the coating identifying the number and gauge of the inner wires. The color of the coating allows you to know what each wire does.
The following is a kind of electric wire type cheatsheet:
- Black wires or “hot wires” carry live electrical charges from the electrical service panel to an electrical outlet, light, or other destination.
- Red wires are hot wires that are used to connect smoke detectors. If one alarm goes off, all the others do, too.
- The white and gray wires are neutral wires that connect to the neutral bus bar, which draws the current and carries it throughout the house. Don’t let the “neutral” part fool you, because they can still carry a load, especially if the current load is not balanced.
- White wires wrapped in black or red electrical tape are also hot wires. The masking tape only indicates that the white wire, which is normally neutral, is used as the hot wire.
- Green wires connect the ground terminal of an outlet box and lead it to a ground bus bar in the electrical panel. This gives the current a place to escape in case a live wire touches metal or other drivers. Green wires can only be connected to other green wires, but they can still be live if the electrical system is faulty.
Bare copper wires are the most common type of ground wire
Blue and yellow wires, although not commonly found in non-metallic (NM) cables, are sometimes used as hot wires in electrical conduits. Blues are travelers who can be on switches at the top and bottom of a staircase to control the same light.
These carry live electrical loads from electrical service panels to electrical outlets.
Red wires are used to interconnect smoke detectors.
White and gray cables
These are neutral wires that connect to the busbar, which draws the current and carries it throughout the house.
What type of cable is used in homes?
Most modern homes use non-metallic (NM) wire that consists of two or more strands wrapped within the aforementioned colored sheathing. The wire bundle typically contains one or more hot wires, plus a neutral and ground.
To accommodate the wiring in an old house or if your wiring just needs some work, you can splice the old wires to the new NM wire using a junction box that protects the wire connections.
The largest wires in the circuit carry a voltage that can be really dangerous to touch. If you don’t know what kind of cables you have, act as if they are all dangerous.
DIY tips for wiring and switching
If you are confident and want to tackle a DIY wiring job on your own, you need to be prepared with information and tools.
Have the right tools. These can include a multimeter that checks electrical voltage and a combination of wire strippers.
Familiarize yourself with the different cables. Make sure you know which color wire goes where and its purpose to avoid electrical shock and to wire your home safely.
Have more cable than you need. Make sure the cable extends at least three inches outside of the electrical box.
Patch the drywall with large plates. Have you made too big a hole in the plaster wall? Fix it with a large electric hob.
Pay for quality. Don’t skimp on the quality of the switches and sockets.
Check the voltage before touching the wires and circuits. The multimeter will let you know if it is safe to touch them.
Investigate. Watch video tutorials on YouTube.
Electrical wiring mistakes to avoid
An electrical oversight can be very serious and cause short circuits, shocks, or fires. These are some of the most common mistakes to avoid:
Never connect cables outside of electrical junction boxes. If there is no box, add one and connect the cables inside it.
Remember the minimum three inches of cable length. Don’t cut the cables too short. If they are, add six-inch extensions.
Never leave siding unprotected between frames, such as in a ceiling installation. Staple the sheathing to a 2×2 or use a metal conduit if the cable runs along the wall.
Avoid loose switches or poorly wired outlets.
Never install a three-slot receptacle without a ground wire.
Do not embed an electrical box behind a wall surface. Instead, add a wall extension.
Secure the cable with a clamp so that the cable insulation does not cut or come apart.
Common electrical problems around the home
If you have old wiring, you probably have a whole host of problems. One of the most common is fraying insulation, as there was no grounding and the wiring was not made to withstand today’s heavy-duty appliances. There are other common electrical problems that are not limited to old wiring:
- Frequent power surges caused by lighting, damaged power lines, or faulty appliances or wiring.
- Dips in power supply due to faulty devices (or devices made of poor quality materials) connected to the electrical network
- Light switches not working properly
- A circuit breaker that trips frequently
- An overloaded circuit breaker
- Lights too bright or too dim
- High electricity bills
- Bulbs that burn out too often
- Recessed lights that turn off and on again