Stacey has been a freelance writer in the home goods and home improvement industry for more than five years, where she’s researched and tested products ranging from mattresses and bathroom cleaners to vacuums and drills. Her work has appeared on Bobvila.com, theSpruce.com, ChicagoNewsTribune.com, TheNewYorkDailyNews.com, and Greatist.com.
Any electrical project around the home requires you to be aware of some common electrical knowledge before you begin. The following is a list of need-to-know tips that will help you feel confident and safe when dealing with your own wiring needs, and steer you well away from looking like the crispy dinner appetizer no one wants to eat.
It's important to note that if you feel at all unsure or out of your depth, there's no shame in hiring a professional. Safety first is always a good rule of thumb when tackling any DIY project!
Before we jump into all of the house electrical wiring types, it pays to get on the same page when it comes to the terminology around common home electrical wiring. House electrical wiring consists of either one thick wire strand made of aluminum or copper, or several strands of conductive wire wrapped together to form and function as a single wire.
Different types of electrical wires and cables run all throughout the average home. For safety purposes, all wires should be insulated with a plastic coating, called insulation, that doesn’t conduct electricity. This insulation isn't just there to protect you, it also acts as a way to prevent the wire from coming into contact with other conductors.
The color of plastic coating used to insulate each wire has a very specific purpose:
Hot wires for outlets and switches, DO NOT TOUCH.
Hot wires for hardwired smoke detectors and switch legs, DO NOT TOUCH.
Hot wires for three- or four-way switches, DO NOT TOUCH.
Hot wires that often control fans and lights, DO NOT TOUCH.
Neutral. Safer than black or red, but err on the side of caution and DO NOT TOUCH. These wires can be hot if marked with red or black.
Ground wire, (in theory) is safe to touch because it doesn’t carry electrical current. That being said, if the wire isn’t properly bonded or there’s faulty equipment involved, it could still shock you. As always, please err on the side of caution.
For the most part, homes built after the 1960s have similar wiring. If your home happens to be older than that, there’s potential for a few surprises. However, many older homes have updated wiring, reflecting these common types of electrical wiring.
Most homes built in the last 50 to 60 years have NM wire (or Romex, named for a popular NM wire brand) throughout their structures. NM wire consists of a cable covered in non-conductive, heat-resistant thermoplastic sheathing. Each cable is made of at least three wires, though sometimes more, with each covered in color-specific insulation.
NM wire is designed for dry places, which is why you’re likely to find it behind drywall and next to insulation throughout your home. The one place you shouldn’t find it is outside. That’s a big no-no.
NM wires come in different gauges or sizes—the higher the number, the smaller the wire. Each gauge carries a certain amperage, which is the amount of electrical current. Under current electrical wiring standards, NM cables have an outer jacket (different from the insulation) that’s color-specific to indicate the gauge. The most common house wire gauge for NM wire, with amps and jacket color, include:
NM cables carry a current. Therefore, they’re dangerous to handle unless you cut the power.
Underground feeder (UF) cables go where NM cables dare not tread, namely, outside and underground. This non-metallic cable consists of hot, neutral, and ground wires, much like NM cable. The difference between the two lies in how the wires are sheathed. In UF cable, the wires are contained in a solid plastic sheathing rather than each being wrapped separately as in NM cable. You can identify UF cable by the gray outer sheath.
While UF cable can be used outside, it shows up in major wiring because it can carry high amounts of voltage. Be careful if you come across UF cable in or around your house. Do not touch the cable unless you’re certain the power is off.
The next electrical wires on this list are THHN and THWN wires. These are individual conductors labeled with color-coded sheathing rather than conductors bundled together as in an NM wire. Each letter in the name stands for a type of wire:
The wires are run through either metal or plastic conduit to unfinished areas of the home, like the garage, to connect the hot water heater.
Colored sheathes help identify the wire’s function, namely:
Like other wires, THHN and THWN wire shouldn’t be handled if it carries a current.
Among the different types of electrical wire, low-voltage wires are among the least dangerous. These thin wires are insulated and come in twisted pairs or in a cable sheath. They connect to low-voltage devices like a doorbell or thermostat. Low-voltage wire cannot be used for anything over 50 volts. Your chances of getting shocked are pretty low, but it’s still a good idea to turn off the device or cut the power before messing with low-voltage wires.
You might not expect to find phone and data wiring on a list of different types of wires with their specifications. However, these low-voltage wires still show up in many homes, so it’s best to know about them in advance.
Telephone cables contain either four or eight wires. However, more common is data, called Cat 5 (short for Category 5) cable, which has eight wires wrapped in pairs. Cat 5 cable is used for data because it can transfer more information than a typical telephone wire.
Phone and data wiring carry under 30 volts, so there’s not much danger here. However, you could still get a slight shock.
Remember the days when coaxial cable was the wave of the future? We’re well past that wave now, but coaxial still shows up. These cables connect televisions to satellite dishes or cable TV services.
Each cable has inner conductors with an insulating layer and a braided wire conducting shield. Coaxial cables are always perfectly round, unlike NM or UF cable. This cable doesn’t carry a very high current, so your chances of getting shocked are pretty small. However, always err on the side of caution.
Whether you’re planning to DIY or just make sure you don’t shock yourself while connecting your cable TV, a little knowledge about electrical wire types and uses can keep you safe. For the electrically adventurous, make sure you’re confident in your wire identification before starting a project. Most importantly, turn off the breaker before touching any wiring.