Wires are usually made of copper or aluminum, these conductive materials act as wire insulation and can supply power to various parts of your home.
Choosing the right wire or cable is half the battle when you are installing new wiring. On the other hand, when inspecting old wiring in your home, identifying the type of wiring can tell you a lot about the circuit the wiring belongs to (for example, if you open a junction box and need to determine which wiring goes where). Wiring in modern homes is fairly standard, and most homes built after the mid-1960s have similar wiring types. Any new electrical installation will require new wiring that complies with local building codes.
Below, learn about the different types of domestic wiring to choose the correct option to complete your electrical project accurately and safely.
It helps to understand some of the basic terms used to describe wiring. A wire is a conductor, a material that conducts electricity. In the case of home wiring, the conductor itself is usually copper or aluminum (or copper sheathed aluminum) and is a solid metal conductor or stranded wire.
Most wires in the home are insulated, which means they are encased in a non-conductive plastic coating. A notable exception is the earth wire, which is usually solid copper and either insulated with a green sheath or uninsulated (bare).
Many of the larger wires in your home carry 120 to 240 volts of circuit voltage, often called line voltage and can be very dangerous to touch. There are several other wires in your home that carry much less "low voltage" current. These are less dangerous and some carry such a low voltage that there is little chance of electric shock. However, until you know exactly what type of wire you are dealing with, it is best to treat them all as dangerous.
Non-metallic (NM) cable, often known by the popular brand name "Romex", is a type of circuit wiring designed for indoor use in dry locations. It consists of two or more individual wires wrapped in a protective plastic jacket.
These conductors are installed with white (usually neutral) and black (usually hot) insulation. Most NM cables have a flat, tubular shape and pass invisibly through the walls, ceiling and floor cavities of your home.
Almost all of the wiring in sockets and light fittings in modern homes is NM cable. This type of wire is used for concealed applications in walls because it is cheaper than using a conduit. The most common sizes and their amperage (amp) ratings are
NM cables are now sold with a colour-coded outer jacket to indicate their gauge.
Grey sheathing is not used for NM cables but is reserved for underground (UF) cables or service entrance cables (SE or SER).
It is dangerous to handle NM cables when the circuit conductors are energized.
An underground feeder (UF) is a non-metallic cable designed for use in wet locations and directly buried underground. It is typically used to supply outdoor fixtures, such as lamp posts. Like the standard NM cable, the UF contains an insulated fire and neutral wire, as well as a bare copper earth wire. However, while the jacket on the NM cable is a separate plastic package, the UF cable jacket is a solid plastic surrounding each wire. This type of wire is also a little more expensive than NM wire because of its durable insulation. UF cable is usually sold with a grey outer sheath.
UF cable is also used for main circuit wiring, which carries dangerous voltages whenever the circuit is opened.
THHN and THWN are the codes for the two most common types of insulated wire used within the conduit. Unlike NM cables, where two or more individually insulated conductors (copper or aluminum) are bundled within a plastic jacket, THHN and THWN wires are single conductors, each with its colour-coded insulation. These wires are not protected by NM cable sheaths, but by tubular metal or plastic conduits.
The conduit is typically used in unfinished areas such as basements and garages, as well as for short periods of exposed wiring inside the home, such as wiring connections for rubbish disposals and water heaters. The price of these wires is usually similar to that of NM wires (plus the cost of the conduit). Letters indicate the specific characteristics of the wire insulation.
THHN and THWN wires have coloured sheaths, which are usually used to identify their function in a circuit.
THHN and THWN wires are electrical lines and should never be handled when opening a circuit.
Low voltage wiring is used for circuits that normally require 50 volts or less. A few common types are landscape lighting wires, sprinkler system connections, bell wires (for doorbells), speaker system wires and thermostat wires. Wire sizes range from approximately 22 gauge to 12 gauge and these wires can be made of copper or aluminum. Low voltage wire is usually insulated and can be contained in a cable sheath or combined into a twisted pair, similar to a lamp wire. It can only be used for low-voltage applications. These are usually very small wires, which are very different from standard circuit wiring, and they tend to cost less than other household wires.
Serious electrical shocks are rare with low-voltage wiring, but it is best to turn off equipment before using it.
Telephone and data cables are low-voltage wires used for 'landline' telephone and internet connections and are usually made of copper. Telephone cables may contain four or eight wires. category 5 (Cat 5) cable is the most common type of domestic data cable and consists of four pairs of eight wires twisted together. It can be used for telephone and data transmission and offers greater capacity and quality than standard telephone cables. As with low-voltage wire, it is usually cheaper than other types of household wire such as NM or UF cable.
Although data cables do carry a small amount of voltage, anything below 30 volts is generally considered safe (domestic circuits carry about 120 volts of power).1 However, there is always a risk of contact with domestic wiring, so data cables should be handled with care and avoid contact with bare wires.
Coaxial cables are starting to become less common due to the use of other forms of data cable (e.g. HDMI) to carry TV data. A coaxial cable is a round sheathed cable characterized by an inner conductor (usually copper) surrounded by tubular insulation and surrounded by a tubular conductive shield made of braided wire. It can be identified by the threaded connectors used for connections and equipment connections.
Coaxial cable was once the standard for connecting a television to an aerial or cable service delivery and is still often used to connect a satellite dish or to bring a subscription television service to a home distribution point. It usually has black or white insulation and is perfectly round, so it is easily distinguishable from NM circuit cables. Affordable coaxial cables are available from most hardware and electronics shops.
Coaxial cable signals carry very little voltage and are therefore unlikely to cause any type of electric shock - provided the cable is not in contact with another current source.
Whether you're replacing old wiring in your home or adding new wiring, it's important to choose the right type. Always choose the cord that is designated for the purpose for which you intend to use it. For example, where it is wet outside, always choose UF wire to ensure that your home's electrical system is protected from the elements. The amperage and volts of each wire should also be considered, and the wire should be matched to the correct needs for each electrical project. If you are unsure of which type of wire you need, it is helpful to consult a professional electrician before you install any type of wire in your home.
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