All electrical projects have one thing in common: electrical wiring. When installing new wiring, it is essential to know what type of wire or cable you need. Having a basic knowledge of electrical wiring types will help you learn more about the current circuits in your home. For example, when looking in a junction box, it will be easy for you to identify which wire goes where.
Modern homes and homes built after the mid-1960s generally have the same type of wire. In addition, any new wiring must comply with requirements established by local building codes or national electrical codes. Electrical wiring is the connection of wires and cables to various devices and equipment such as appliances, switches, lights, outlets, etc. at the main switchboard.
Cable against Wire
It is important to understand some of the basic terms used to describe wiring. An electric wire is a conductor, a material that conducts electricity. For household wiring, the material is either copper or aluminum (or copper-clad aluminum), although aluminum is not really used anymore. It can be stranded wire or a solid metal conductor and in most cases is insulated with a non-conductive plastic coating.
On the other hand, a cable is a combination of two or more wires, which are put together using a sheath. In modern homes, NM (non-metallic) cable is the most common type. It consists of two or more separate wires wrapped inside a protective plastic sheath and composed of:
one or more “hot” wires (current conductors)
a neutral wire
a ground wire
1. NM cable
The most common type of household electrical wiring is NM cable, also known as Romex cable after the most popular brand of electrical wiring. NM cable consists of three or more individual conductors wrapped together in a sheath, which is a flexible plastic sheath.
This type of cable is typically used for dry internal household wiring and includes appliances, light fixtures, switches, and outlets. Today, NM cables are color-coded, which means that the outer jacket of the cable is available in different colors to indicate the gauge of the wire. Here are the most common NM cables that you will most often find in modern homes:
55 Amp 6 gauge circuits come with a black jacket
8 gauge and 40 amp circuits come with a black jacket
10 and 30 amp gauge circuits come with an orange jacket
12 gauge and 20 amp circuits come with a yellow jacket
14 gauge and 15 amp circuits come with a white jacket
The gray sheath is reserved for underground cables (UF).
2. Shielded cable
When it comes to electrical wiring, local ordinances are stricter than national codes. This is why you may find that the use of NM cables is not allowed in some areas and shielded or AC cables are used in these locations.
AC wiring, also known as BX, dates back to the early 1900s and is designed with a flexible metal jacket, which provides additional protection for the conductors inside. Air conditioners cannot be used in commercial buildings or residential constructions higher than three stories.
3. Underground power cable
UF (Underground Feeder) is an NM cable specially designed for damp locations and directly buried in the ground. When running wires underground or in outdoor projects, you must use UF cables. Another option chosen by electricians is to run PVC conduit underground and run the wires.
This type of cable is typically used to power outdoor light fixtures and consists of insulated hot and neutral wires, as well as a bare ground wire. Unlike the NM cable, the UF type has a strong plastic sheath around each wire and a gray outer sheath. In addition, this type of cable can be used for major circuit wiring.
4. Low voltage wire
Low voltage wiring is used for circuits that use less than 50 volts. This type of wiring is the perfect choice for items that don’t require a lot of electricity, such as doorbells, thermostats, sprinkler systems, or landscape lighting.
Low voltage wiring ranges from 12 to 22 gauge and is either insulated or covered with a cable sheath. Although shocks generally do not occur with low voltage wiring, it is advisable to turn off your equipment before beginning to work with them.
5. THHN/THWN WIRE
THHN and THWN are the two most common types of insulated wire. Unlike NM cables, these are single conductors, each with color-coded insulation. And they are protected by a plastic or tubular metal conduit.
Hotwires are black, orange, or red;
The neutral wire is white or grey;
Ground wires are green or yellow-green.
With regard to insulation, the letters designate their properties:
T stands for thermoplastic;
H stands for heat resistant and HH is very heat resistant;
W means rated for wet locations;
N stands for nylon coated for extra protection.
This type of wiring should only be used in areas such as basements or garages, and indoors, for short exposed distances, such as wiring connections to a water heater or disposal garbage. Since these circuits are wires, they should never be handled with a current circuit.
6. Telephone and data wire
Telephone and internet wiring both use low voltage wires. Although the most common type of cable for this is Cat (Category) 5, your phone and data cables may have four to eight wires. Category 5 cable has eight wires wound together in four pairs and is the most efficient type for telephone and data transmission. Additionally, Cat 5 cable brings more capacity and quality than standard telephone wire.
Even if the data wiring does not carry high voltage, it is still dangerous for the data wiring to come into contact with household wiring. Therefore, treat it with care and avoid touching bare wires.