Learn the Basics of Home Electrical Wiring

If you need help with your electrical wiring, call Mister Sparky® of San Antonio at (210) 899-2430 and we’ll send one of our professionals to assist you.

Understanding the Colors of Electrical Wires: The Basics

When trying to understand your home’s electrical system, you may encounter a tangle of colored wires. Here’s what those colors mean, and a few things to keep in mind when checking your wiring system. If your home is older or you’re having difficulty with your home’s wiring system, we recommend you utilize a certified electrician.

• What are Black Wires?
  First, you should always be aware of which wires may pose a safety hazard. Black, red, white with black or red tape will always indicate a hot wire. The term “hot” means these wires carry a live current from your electric panel to the destination. While white wiring is permitted— only when clearly marked with black or white tape—using any other color for a wire carrying current is strongly discouraged. This may pose a serious safety hazard that could result in death. Black or red wires always carry power from the service panel (breaker box) to your home’s devices.
• What are Red Wires?
  Red wires are usually used as secondary hot wires. Red wires are also hot and should be clearly marked to avoid the dangers of electrocution. Red wires are commonly used when installing ceiling fans, where the light switch maybe.
• What are Green Wires?
  Green insulated wires are often used for grounding. Ground screws on electrical devices are often painted green, too. Never use a green wire for any purpose other than for grounding, as this may pose a serious threat of electrocution for you or a professional working on your home’s electrical system.
• What are White Wires?
  White or gray wires indicate neutral charged wires. However, neutral wires may carry power and pose a danger of electrocution if not handled properly. White and gray wires carry power back to the service panel. Both hot and neutral wires have the potential to shock and injure you if not handled properly.
• What are Blue and Yellow Wires?
  Blue and yellow wires are sometimes used as hot wires. Blue wires are commonly used for travelers in three-way and four-way switch applications.

A multimeter will help you check and troubleshoot your home’s electrical wiring system. The multimeter can be used to check if there is an electric current flowing and how much. This can be especially useful if your home’s electrical system is old, outdated, or if you are unsure which wires may be hot or not.

If you need help with your electrical wiring, call Mister Sparky® of San Antonio at (210) 899-2430 and we’ll send one of our professionals to assist you.

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Learn the Basics of Home Electrical Wiring

Electrical wiring can be tricky—especially for the novice. That’s why it’s usually best to hire a professional for anything other than a simple job. Otherwise, you could risk injury, damage or fire. If you do plan to complete a DIY project that has an electrical component, there are some basic things to know about wiring installation.

Understanding electrical wiring

Since the 1940s, any house built (or any older home that has been rewired) has had to follow an electrical code: the NEC—written with safety in mind. NEC code identifies types of electrical wires and electrical cable types by color. When you remove a switch plate, you’ve probably noticed yellow, white, black, red or green wires. They are not there to be decorative; each serves a specific purpose, and some don’t play nicely with others.

How to electrical wires

When you’re doing wiring installation, you need to identify the parts of the wiring cable, the non-metallic electrical cable: the outer sheathing (the jacket) and the inner wires. The colored “wire” you see—the green, black, red, blue or white—is actually the sheathing that covers the inner copper wires. If you look closely, you’ll see markings stamped on the sheathing to let you know the number and gauge of wires inside. The color of the sheathing lets you know what each wire does.

The following is sort of an electrical wire types chart:

• Black wires or “hot wires” carry live electrical loads from the electrical service panel to an outlet, light or other destination.
• Red wires are also hot wires used to interconnect smoke detectors, so that if one alarm goes off, all the others do as well.
• White and gray wires are neutral wires that connect to the neutral bus bar, which attracts current and carries it throughout the house. Don’t let the “neutral” part fool you because they can still carry a charge—especially if the current load is not balanced.
• White wires wrapped in black or red electrical tape are also hot wires. The tape just lets you know that the white wire, which is normally neutral, is being used as a hot wire instead.
• Green wires connect the grounding terminal in an outlet box and run it to a ground bus bar in the electrical panel, giving current a place to escape to the ground in the event a live wire touches metal or another conductor. Green wires can only connect to other green wires but can still be live if the electrical system is faulty.
• Bare copper wires are the most common type of grounding wires.
• Blue and yellow wires, although not usually found in non-metallic (NM) cable, are sometimes used as hot wires in an electrical conduit. The blue ones are travelers that might be in the switches at both the top and bottom of a staircase to control the same light.

Carries live electrical loads from the electrical service panel to an outlet
Used to interconnect smoke detectors, so that if one alarm goes off.

Are neutral wires that connect to the neutral bus bar, which attracts current and carries it throughout the house.

What type of wire is used for residential?

Most modern homes use nonmetallic (NM) cable that consists of two or more wires wrapped inside the colored sheathing mentioned previously. The package of wires usually contains one or more hot wires plus a neutral and a ground. To accommodate wiring in an older home or if your wiring just needs work, you can splice the old wires with new NM cable using a junction box that protects wire connections. The larger circuit wires carry circuit voltage that can be really dangerous to touch. If you don’t know what kind of wires you have, consider them all to be dangerous.