The Electrical Infrastructure in a home consists of Electric Wires and Cables. For a successful wiring, you need to use a proper wire which is correct in size and type. But what exactly is the difference between a Wire and a Cable? What are the Different Types of Electric Wire? In this guide, let us explore the basics of electrical wires and cables and also types of electric wire that are frequently used in residential wiring.
A Brief Note on Electric Wire and Cable
An Electric Wire is a conductor of electricity that carries electric current to a device such as a light or an appliance. While Copper is the most common conductor, Aluminum and Copper coated Aluminum are also popular. An electric wire is usually a single conductor. It can consist of a single solid conductor or multiple strands of conductors.
All wires have an insulation on top of the conductors as the electricity travels on the surface of the wire. This insulation is usually PVC and provides protection against electric shocks and fires. The PVC insulation is colored to indicate the function of the wire. For example, in the U.S., we use wires with black PVC insulation for live (hot) in AC Mains wiring and one with white (or gray) insulation as neutral.
If two or more wires are grouped together and enclosed in a plastic (or rubber or metal) sheath, then it is known as a Cable. The individual wires in the cable are still insulated with color codes. If you take a look at the service entrance cable coming form your utility to your main circuit breaker panel, then you will notice it has three wires inside it: black hot wire, white neutral wire and a bare copper wire for ground.
Another important parameter associated with electric wires and cables is their current carrying capacity (or amperage). The American Wire Gauge (AWG) is a standard system for defining the wire gauges and its capacity. For instance, a gauge #10 wire is rated for 30A and 240V (dryers and air conditioners) while a gauge #14 is rated for 15A and 120V (household receptacles and light fixtures).
Types of Electric Wire
Depending on the application, we have different types of electric wire. Some of the wires mentioned in this guide are used for carrying electricity only while some wires carry electrical signals (such as telephone and internet).
Having a basic knowledge of all these essential wires that are used in a typical residential electrical system is very helpful. If you are working on an electrical repair project or installing a new wiring, then selecting the correct type of electrical wire is crucial.
Here is a list of some of the popular types of electric wire that we commonly use in residential wiring.
- Non-Metallic (NM) Sheathed Cable
- Service Entrance (SE) Cable
- Underground Feeder (UF) Cable
- THHN/THWN Wire
- Low Voltage Wire
- Armored Cable (AC)
- Coaxial Cable
- Phone and Data Wire
Let us now quickly see about all these different types of electric wire with their internal layout and applications.
Non-Metallic (NM) Sheathed Cable
The electric wiring in indoor residential and dry locations is usually done with NM Sheathed Cable. As the name suggests, an NM Cables has a non-metallic sheathing, usually PVC.
Earlier, the Rome Wire and Cable Company manufactured these cables with a trademark of Romex. Hence, most electricians call an NM Cable as a Romex cable. Now, the Southwire Company owns the Romex trademark.
NM Cables come in two variants: 2-wire with ground and 3-wire with ground. The “2-wire with ground” type NM Cable has a black conductor (hot), a white conductor (neutral) and a bare copper ground wire.
The “3-wire with ground” type has an additional red conductor (hot) for wiring 240V circuits. There are again three types of NM Cables.
- NM-B: This is the most common type of NM Cable. These cables are flame retardant, moisture resistant and have a non-metallic outer sheathing.
- NMC-B: In addition to being flame retardant and moisture resistant, these cables are also fungus resistant and corrosion resistant.
- NMS-B: A hybrid cable that contains “2-wire with ground” power conductors and also telephone, coaxial and home entertainment conductors.
NOTE: The suffix B in above cables indicate the thermal insulation capabilities. It means the cables have 90°C insulation. This suffix will help you identify newer NM cables as old NM cables without any suffix are rated only for 60°C.
Depending on the application and installation, you can use NM Cables with different gauges and amperage.
Service Entrance (SE) Cable
You might have guessed from the name itself. A Service Entrance Cable is the main cable that comes from your power utility (usually from a distribution pole transformer) and connects to your building’s main service panel. The live (hot) and neutral wires consist of multiple strands of conductors instead of a single solid conductor.
Like NM Cables, even service entrance cables are also available as 2-wire with ground and 3-wire with ground configurations. As they usually have high amperage, you can use these cables for wiring large appliances (50A or 60A) as well.
Underground Feeder (UF) Cable
As regular NM cables are not suitable for wet locations, the Underground Feeder (UF) cables fill that gap. They are a type of NM Cables that are designed for wiring in wet/damp locations, underground wiring and other locations where regular NM cable are not usable.
All the wires in a UF Cable are grouped together with a solid thermoplastic sheathing. Similar to NM Cables, the UF Cables are also available with different gauge wires.
THHN/THWN Wire
If you want to run wiring through conduits, then you need wires with THHN/THWN rating. These wires are individual wires instead of cables and you have purchase them separately. The live and neutral wires have color coded thermoplastic insulation.
As these wires are meant for conduits, the ground wire is also insulated with green color coding. THHN means the type of insulation, which is Thermoplastic High Heat-Resistant Nylon Coated wire. THWN also means the same but the ‘W’ stands for wet insulation.
Armored Cable (AC)
Some old homes don’t have NM or UF Cables. Here, you will find Armored Cable (AC). An AC cable consists of insulated hot and neutral wires and a bare grounding wire. The insulator is usually paper.
Coming to the outer protection, it has a metal sheathing. Modern homes don’t use Armored Cables as NM or UF Cables replaced them over the years.
Low Voltage Wire
If you have any low voltage circuits such as doorbells, thermostats, sprinklers or any low-voltage lighting, then you need a Low Voltage Wire. The voltage rating is usually 50V or less. The gauges of low voltage wires can be anywhere between #12 to #22.
Coaxial Cable
The next couple of wires are not for carrying electricity but they carry electrical signals. First, we have the famous coaxial cable. These cables are very popular for cable television. Even if you have a satellite connection, the connection between the parabolic dish antenna (on the roof top) and the receiver box (in the home) is usually a coaxial cable.
These cables consist of just a single conductor with a round tubular insulation. A braided metal wire covers the insulation and it acts as a ground conductor. There is a PVC insulation on top of that.
Phone and Data Wire
Landline telephones are gradually becoming part of history but if you happen to have one, then you have to use a dedicated telephone cable. RJ11 cables are very common telephone wires.
Coming to Internet data cable, Cat5, Cat5E, Cat6 and Cat6E based twisted pair cables.
Conclusion
Electric Wires form the main infrastructure of residential wiring. We can use wires or cables for wiring and depending on the application, we have different types of electric wire. We saw the differences between wire and cable, types of electric wires along with their applications.
