The ultimate guide to types of domestic electrical wiring - knoweasy

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The ultimate guide to types of domestic electrical wiring

October 16, 2022


The ultimate guide to the types of electrical wiring used in the home

Becoming an apprentice electrician can take as little as 100 hours in trade school to earn a four-year degree at university. This should tell you how much training and knowledge you need to become a licensed electrician.

But understanding the basics of electrical wiring in your home doesn't have to be that in-depth.

Also, if you're doing a simple DIY electrical project around the house, you'll need to know the different types of wiring in your home.

You should also be aware of standard sizes, codes, labels and usage.

Luckily, we've broken down everything you need to know in this ultimate guide to household wire types.

Let's get started.


Why do you need to know about the electrical wiring in your home?


If you're doing any type of electrical project around the house, it's best to have a little knowledge of the electrical wiring you'll encounter.

A little electrical knowledge will allow you to work safely and efficiently. There are different types of electrical wiring you will need to know about in the following situations:

  • Installing new wiring (you need to know which type of wire to use)
  • Solving electrical problems around the home (knowing the circuit the wiring belongs to can help you determine the cause of the problem)
  • Carrying out electrical repairs
  • Remodeling

Before we go any further, we should tell you that any changes you make to the wiring in your home must be up to code and comply with the National Electrical Code and local ordinances.

Local codes are often more stringent and should be strictly adhered to to prevent any errors.

Failure to comply with the required codes and regulations can increase the risk of hazards such as fire.

Also, if you decide to sell your home and an inspector finds it, you may have to spend more money to correct the problem than if you had done it right the first time and hired a professional electrician.


The basics of domestic electrical wiring


Before we dive into the types of domestic electrical wiring, you should understand some basic terminology, coding and labeling standards.

If you understand these conventions, you can ensure a more comfortable journey to the hardware or electrical shop.


Wires and cables


Believe it or not, cables and wires are not the same things. Shocking? (See what we did there?)

Wires are defined as "any material that conducts electricity". They are separate conductors in a jacket and can be either insulated or bare.

Cables, on the other hand, are any combination of two or more wires, assembled from a single jacket.


Colour coding of cable jackets


The outer sheath of a cable is color coded to inform you of the size of the wires inside the cable. The color code also indicates the current strength of the cable.

The following are typical colors and their associated dimensions and current strengths.

  • Black. 8 or 6-gauge wire, 45 or 60-amp circuit
  • Orange. 10 gauge wire, 30 amp circuit
  • Yellow. 12 gauge, 20 amp circuit
  • White. 14 gauge wire, 15 amp circuit

If you see a grey cable, it is an underground feeder (UF) cable. All UF cables are grey. To find out the specifications and circuit information of the UF cable, it is necessary to check the cable jacket label.

Cable sheath color coding is relatively innovative. It was not introduced to the electrical industry until 2001.

Companies are not even obliged to use it, so you should always contact the manufacturer of the cable to ensure that the color coding is in line with current standards.


Colour coding of electrical cables


In contrast to cable sheath color coding, wire color coding is the standard for all conductors. House wiring is usually limited to the following colors.

  • White - neutral wire that completes the circuit by carrying current back to the panel.
  • Black/Red - Hot wire that carries current from a circuit breaker or panel to a device such as a socket, switch, light fixture or appliance.
  • Green / Bare - A path for current to return to the circuit breaker, blow a fuse and cut off power in the event of a ground fault.

There are other wire colors, but these are the ones you are most likely to encounter in your home.

By knowing what each wire represents, you can better understand its role in the overall structure of your home's electrical system.



In addition to the color coding on the sheath, both wires and cables use labels to provide you with information on



  • Number of wires in the cable
  • Type of insulation
  • Other ratings

These labels are printed on the wire insulation or the outer sheath of the cable.


Wire size


When you hear the term "wire size", it refers to the diameter of the actual conductor. Interesting fact: the US wire gauge system, in short, the smaller the wire, the larger the gauge.

It is important to know that the wire sizes you choose must match the amperage of the circuit they are used on. If they do not match, the risk of short circuits and fires is significantly increased.

The gauge of the wire determines its current carrying capacity. 


What is the current carrying capacity?


The current carrying capacity is the number of amperes the wire can safely handle.

Household electrical wiring is usually size 12 or 14, unless you are using it for an appliance. In that case, you would use a 10, 8 or 6 gauge.  

Appliances such as furnaces, dryers, water heaters, heaters and air conditioning units require larger gauge wires because they draw more current.


Stranded vs. solid wire


If you need to run a wire through a conduit, use a solid wire. Conversely, if you need to pull a wire through a conduit, consider using stranded wire. Because it is more flexible, stranded wire is easier to get around hard-to-reach areas and corners.


What types of electrical wiring are available in the home?


There are several types of wires and cables that can be found in and around your home.

Let's go into more detail.


Non-metallic (NM) cables


If your house was built around the mid-1960s, then it probably has NM cables.

NM cable is the most common type of domestic wire. You may have heard it referred to as Romex, which is the brand name for this type of wire.

You know, kind of like in South Louisiana, any weed whacker is "weed killer" and any soft drink is "Coke".

But we digress back to NM cables.

NM cables usually have three or more separate conductors wrapped in a flexible plastic jacket (sheath). An NM cable usually has a firewire, an earth wire and a zero wire in it.

Non-metallic cables are used for indoor domestic wiring in dry environments. NM cables are commonly used for appliances, junction boxes, lamps and sockets and the most common NM sizes found in modern homes are:

  • 14 gauge, 15 amp circuits
  • 12 gauge, 20 amp circuit
  • 10 gauge, 30 amp circuit
  • 8 gauge, 40 amp circuit
  • 6 gauge 55 amp circuit

In some cases, the wiring in your home may be installed in conduit, flexible metal or plastic tubing, but this is usually when your wires are exposed.


NM Cable Regulations


Before we move on to the next type of wiring in your home, we think you should be aware of a few regulations regarding NM cables.

Firstly, NM cables cannot be used in residential buildings over three stories. Although designed strictly for domestic use, NM cables are prohibited for commercial applications.

As with anything code-oriented, variances and deviations are always allowed, so if you have any questions, it's best to consult your local building official.

Secondly, NM Cable is designed as a permanent domestic wiring system and should not be used as a replacement for extension cords and not as a wiring pigtail for appliances.

Finally, you must fully support NM Cable where necessary. The use of nails or staples is prohibited and anything that could damage the cable is not allowed as support. In addition, NM cables should be secured at intervals of no more than 4.5 feet.


Armored cables


As we mentioned before, local domestic wiring regulations are often stricter than national codes.

In some communities, NM (Romex) cables are not allowed. Instead, these locals require the use of armored cable (or AC).

This type of wire, also known as BX, has been in use since the early 1900s and is still in use today.

AC wire has a flexible metal sheath that provides additional protection for the internal conductors.

As with NM cables, AC (BX) is not permitted in residential or commercial buildings over three stories.  

The rules and regulations for supporting armored cables are similar to those for unarmoured cables, but again, if you have any questions, it is best to consult your local building official.


Underground feeders


Armored (AC) and non-metallic (NM) cables are used for dry indoor conditions, while underground feeder (UF) cables are designed for outdoor or wet conditions.

When you need to run wire for an outdoor project or underground, you need to use UF cable, a non-metallic cable that can be buried underground without a conduit and can get wet without any problems.

Just like NM cables, UF cables consist of three wires.

  • A hot wire
  • a neutral wire
  • A bare earth wire


Metal-clad cables


Metal-clad cables are often used when wires are run through unfinished areas such as basements. Even though we don't have many basements in South Louisiana, we will continue to.

If your wiring is exposed and at risk of physical damage, use metal-clad cable.


Low voltage wiring


Low voltage wiring is permitted for any circuit that uses less than 50 volts (items that do not require significant power), such as

  • doorbells
  • Thermostats
  • Landscape Lighting
  • Alarm systems
  • CCTV

Low voltage wires are available in sizes from 12 to 22 and are usually insulated or covered in a cable sheath.


Telephone and data cables

Your telephone (landline) and internet use low-voltage wires. Although your telephone and data cables may contain four to eight wires, the most common type of cable used for these purposes is Category 5 (Cat 5).

Cat 5 cable looks like a large telephone cable (if you remember) and it consists of four pairs of eight wires twisted together.


Key points


Your home's wiring system is complex. But by now (hopefully), you have a better understanding of its components and are better prepared to diagnose problems, complete repairs and plan renovations.

Now that you have read this ultimate guide to domestic electrical wiring, we hope you have a better grasp of:

  • The relationship between size and amperage
  • The world of cable sheathing and wire coding
  • How to read a cable or wire label
  • The difference between wire and cable
  • When to use solid versus stranded wire
  • How to choose the right wire for your application
  • But don't go beyond yourself. Knowing and understanding your home's electrical system does not necessarily qualify you to repair or replace it.

When it comes to your home's electrical system, you are best suited to seek the help of a professional.


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