Cable & Wires

All You Need to Know About Electric Wiring of Your House

All You Need to Know About Electric Wiring of Your House

Knowing the basic wire types is essential for almost any electrical project in your home. For example, choosing the right cable or cable when installing a new cable is half the battle. Wiring is pretty much standard in modern homes, and most homes built after the mid-1960s have similar wiring. All new electrical systems require new wiring by local building codes.

Here are some common types of home electrical wire.

Wiring Terminology

 It will help you understand some basic terms used to describe wiring. The wire is a conductor made from a material that conducts electricity. In household wiring, the conductor is usually made from copper or aluminum (or copper-clad aluminum), which is a hard metal conductor or filament wire. Most house wiring is insulated. They are wrapped with a layer of non-conductive plastic. One notable exception is the ground wire. It is usually pure or insulated copper with a green or non-insulating (bare) cap.

Cable terminology

The most common type of cable in modern homes is non-metallic (NM) cable. It consists of two or more individual wires wrapped in a protective plastic sheath. NM cables usually consist of one or more wires: a neutral wire and a ground wire. Instead of NM cables, individual wires can be inserted into rigid or flexible metal or plastic pipes called conduits.

Cable trays are often used where cables are exposed and not covered by walls, floors, or ceilings. These large wires carry circuit voltage throughout the house and are very dangerous to touch.  

NM Cable

NM cables are often referred to as Romex; a brand for round wires for indoor and dry use. Most NM cables have a flat tube that passes invisibly through gaps in walls and floors. Almost all socket cords and modern household lamps are NM cables.

The most common sizes and current ratings in amperes are:

  • Gauge 14 (15 amp-circuits)
  • Gauge 12 (20 amp-circuits)
  • Gauge 10 (30 amp-circuits)
  • Gauge 8 (40 amp-circuits)
  • Gauge 6 (55 amp-circuits)

Cables are currently sold with colored outer casings to indicate conductor cross-sections which are explained as follows:

White sheath: 14-gauge conductor NM cable

Yellow sheath: 12-gauge conductor NM cable

Orange sheath:  10-gauge conductor NM cable

 Black sheath:  6-8-gauge conductor NM cable

Grey sheath: Reserved for underground wiring only.

It is important to note that it is dangerous to handle Nm cables when the circuit conductors carry voltage.

UF Cable

Underground Feeder (UF) is a non-metallic cable designed for wet areas and direct burial. Widely used in supplying outdoor lighting fixtures such as light towers. Like standard NM cables, the UF consists of a high temperature, neutral wire, and an insulated ground wire. The NM cable jacket is a separate plastic jacket whereas the UF cable jacket is a solid plastic surrounding each wire. UF cables are usually sold with a grey outer jacket. This is because the UF cable is connected to the main circuit and carries a dangerous amount of voltage flow during circuit operation.


THHN and THWN are the two most common types of insulated cables used in pipes. Unlike NM cables, where two or more insulated conductors are connected by a plastic sheath, THHN and THWN wires are two separate conductors each with colored insulation.

 Instead of shielding the NM cables, these wires are protected by a metal or plastic tube. These pipes are often used in structural areas such as basements and garages, and for short-term household purposes such as cabling. For drains and hot water boilers, the letters indicate special insulating properties of the wires which are explained as follows:  

  • T: Thermoplastic
  • H: Heat resistance
  • HH stands for high heat resistance
  • W: Suitable for wet locations
  • N: Nylon sheaths for additional protection

THWN and THHN are usually marked with colors used to identify the function of the circuit with sheath:

Hot cables: Black, Red, Orange  

Neutral Wires: White and Brown

Ground Wire: Green, Yellow

It is important to note that THHN and THWN wires are round wires and must not be used when working on electrical circuits.

Low-Voltage Wire

 Low voltage wiring is typically used for circuits that require 50 volts or less. The most common types are landscape lighting cables, irrigation system connections, alarm cables (for door alarms), speaker system cables, and thermostat cables. Cable sizes vary from 22 gauge to 12 gauge, and low voltage cables are usually insulated and can be inserted into conduits or run-in twisted pairs such as lamp cables. These cables are usually very short and, unlike standard circuit cables, low voltage cables rarely cause strong shocks, but it is recommended to turn off the equipment before handling.

Phone and Data Wire

Phone and data cables are low-voltage cables used for landlines, phone connections, and the Internet. Telephone cables have either 4 or 8 conductors. Class 5 (Cat 5) cables are the most common type of household data cable consisting of four pairs and eight conductors. It can be used for both telephonic and data transmission. It offers greater capacity and quality than traditional telephone cables. Always be careful not to touch the exposed cables as there is always a risk of the data cables coming in contact with household cables.

Coaxial Cable

Coaxial cables are slowly evolving as a way to transmit TV data using other types of data cables, such as HDMI. A coaxial cable is a sheathed cable in which the inner conductor is surrounded by a tubular insulating layer and a tubular conductive screen made of filament wire. This can be seen in the connection of devices and the threaded connections used to make unions.

Coaxial cable was once the standard for connecting TVs to antennas and cable services. It is still used today as it connects satellite dishes and provides shared TV services to home distribution points. The insulation is usually black or white and has a perfectly round shape, making it easy to identify cables containing NM electric circuit cables.

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