Types of Electrical Wiring Used in Homes

Simply put, electricity is a blessing to humanity.

It is the current flow through a conductive material that can potentially do useful work or wreak havoc.

Just like fire, electricity can either be a faithful servant or a vicious master. A set of conventions must be followed strictly for its useful and safe deployment.

Similarly, household wiring follows specific protocols and conventions without which the household electrical items cannot work optimally and, in effect, become prone to damage. The electrical engineer or electrician is saddled with the responsibility of following these rules.

This is to avoid the risk of shock or injury to residents.

The protocols seem overwhelming taken as a whole. But broken down (as we’re about to do), they hold no mystery.

 

Wires and Cables: The Distinction

The two words 'wire' and 'cable' are used interchangeably and are taken to mean the same thing, but they’re not.

A wire is a length of conductive material, usually made of bare, twisted strands of copper or aluminum. It is clad in an insulating material like PVC to prevent shock.

Wires are measured using their diameter and assigned a gauge number. The gauge numbers assigned determine the thickness of the wires and their current-carrying capacities.

The thickness can sometimes be expressed in terms of the wire's cross-sectional area (mm²). Smaller gauge numbers mean thick wires, which translates to higher amperage (from the word ampere, the unit for measuring current).

Popular gauges used today and their corresponding amperage are:

• 14 gauge - 15amps capacity
• 12 gauge - 20amps capacity
• 10 gauge - 30amps capacity
• 8 gauge - 40amps capacity
• 6 gauge - 55amps capacity

The 10 and 20 gauge wires are typically used for home wiring.

Cables, on the other hand, are a cluster of two or more (insulated) wires wrapped together as one in another insulator jacket.

In domestic wiring, the cable usually carries one or two hot (or live) wires, the neutral wire, and the grounding (or earth) wire.

The live wire carries the current from the source of electricity; the neural wire returns it to the source and, in effect, makes a close electrical loop called a circuit.

Apart from electricity, cables can be made to transmit telecommunication signals.

 

Different Types of Cables Used in Home Wiring (and Their Uses)

In domestic electrical installations, the wire gauge to be used depends on the current usage of the home appliances to be installed.

For example, a fan typically requires less current to operate than an air conditioning system. Hence, a thicker cable is used to connect the air conditioner while a thinner one is used for the fan.

The home cable needs also vary broadly, in the sense that different types of cables serve different purposes. For example, coaxial cable is used for telephone connections around the home.

Below is a list of wires/cables used in homes, classified according to their purposes.

 

Image credit to AB Electrical & Communications Ltd

The Non-metallic (NM) Cable

This is by far the most commonly used cable in domestic wiring. It is made up of three or more color-coded wires. This means that the live (or hot), neutral, and ground wires are assigned a particular color according to electrical conventions.

The wires come insulated in heat-resistant thermoplastic jackets.

They’re made for the dry indoor environment. For this reason, they cannot be used outdoors because of the risk of environmental degradation, hence, exposing people to harm.

Below is a list of standard NM cable specifications adopted for some common home appliances.

• 2.5mm² diameter used for sockets
• 4.0mm² diameter used for dishwashers, electric cookers, washing machines, dryers, and so on
• 5.0mm² diameter used for automation and general lighting
• 6.0mm² diameter used for air conditioning systems, electric ovens, and the likes

 

Armored Cable

The armored cables offer extra protection for the wires within the cables. They’re favored over NM cables in areas where local electrical policies are rigorous. However, they cannot be used in domestic buildings higher than three stories.

 

Underground Feeder Cables

Initialized as UF, these cables are NM cables with the capacity for outdoor applications. However, unlike NM cables, UF cables have strong plastic sheaths around each wire, covered by a grey outer jacket.

They are specially designed for humid, wet, or moist environments and can be buried underground, hence their name 'underground' feeder. The cables are generally used to supply outdoor electrical accessories like lamps.

 

Low-Voltage Wire

Some circuits like the doorbell circuits, thermostat, and garden sprinklers only require small voltages (50volts or less). The caliber of wire thickness required is usually between 10 and 22 gauge.

 

THHN and THWN Cables

These wires are used domestically in the basement of houses or garages for wiring circuits used for water heating and waste disposal.

The THHN and THWN cables are single conductor cables. This means that they are composed of a single solid conductor rather than several tiny conductors to make up a wire. They can come protected either by a plastic insulator or metallic conduit.

The letters used in the naming of these cables have their significance:

• T - Thermoplastic: This indicates that the cable is fire resistant
• H/HH - Heat resistance: This value indicates that the cable can withstand heat up to 167°F (for H) and 194°F (for HH)
• W - Suitable for wet locations
• N- Nylon quoted: for extra protection

 

Others

• Twisted pair cable: This is made up of a pair of twisted wires that can be used for telephone and Ethernet connections around the home.
• Coaxial cable: Consists of an inner single insulated core wire surrounded by an outer array of foil wires covered in PVC. It is typically used for TV connections in homes.

 

Series vs Parallel Circuits

To connect the electrical appliances and accessories in the home, one of two wiring methods can be adopted: parallel or series connection. The parallel connection is, however, the more efficient method.

 

Parallel Circuits

An electrical circuit consists of elements like lamps, fans, junctions, and sockets connected by cables. The connection is parallel when the various electrical components are powered by only one circuit.

The connection is such that the hot and neutral wires pass through the electrical junctions from which the various elements take their sources. The parallel type of connection ensures that a failure in one electrical appliance (or component) does not bring the whole circuit to its knees.

 

Series Circuits

The series connection is not commonly used in home electrical installation. In this case, the live wire is passed through every element on the electric circuit, and the last element's terminal is joined to the neutral wire to form a closed electrical circuit.

The series connection has useful applications in the making of Christmas light and other fancy lighting used for decoration. The shortcoming of a series circuit is that a fault in one element (for example, one light in the Christmas light) leads to the failure of the entire circuit.

 

Electrical Cables and Wires Color Codes

Cable Color Codes

The outer jackets of cables follow a color code convention to tell you on sight the size and amperage of the cables. Below are the standard color codes for cables.

• White - 14 gauge / 15 amps
• Yellow - 12 gauge / 20 amps
• Orange - 10 gauge / 30 amps
• Black - 6 or 8 gauge / 45 or 60 amps respectively
• Grey - These are underground feeders (UF). The gauge of a UF cable can typically be seen written on the label of the cable jacket

 

Wires Color Codes

• Black/red: These are live (or hot) wires meant to carry electrical current from the source into the element that utilizes them.
• Green: They are the ground wires. They take excess current into the ground in the event of an electrical surge or fault. The ground wires establish a route for returning the current into the circuit breaker and trips off the electricity, effectively saving your appliance from damage.
• White: These are neutral wires meant to carry the current back to the source, thereby completing the electric circuit.

 

The Conduit Wiring System

The conduit wiring system is favored for household wiring and can be divided into two: surface conduit and concealed conduit wiring systems.

 

• Surface Conduit Wiring

It employs recessed PVC tubes called conduits attached to the walls or roof. The laid wires can run throughout the building through the conduit fixtures.

 

• Concealed Conduit Wiring

In this system, the conduits are hidden inside the walls so that no wires can be visible.

 

Conclusion

The codes and protocols involved in electrical home installation can be overwhelming when taken as one. The bulk of the work should be left to qualified and professional personnel -electrical technicians and engineers.

With this article, you know what terms to use if you need to relay the cause of a fault or probably purchase a new cable to replace a faulty one.