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Electrical Wire Types & Colour Codes

There are many different types and sizes of electrical wire, all used for different applications throughout your home. We’ll show you the differences and help you choose the right wire for your job in this handy guide.

Important: Before starting any job, consult the most recent Canadian Electrical Code (CEC), local codes or a licensed electrician for further information related to applications.

Understanding Key Electrical Concepts

Here are some of the most common electrical terms and their meanings:

Wire vs Cable Wire is a single component (one conductor, insulated or not) while cable is an assembly of those components, containing insulated wires. Wire/cable can be copper or aluminum.
Conductor Is the metal component of a wire, commonly made of aluminum or copper.
Gauge
The size or gauge of the conductor. Copper conductors can carry bigger current and the larger the conductor, the more current it can safely carry.
Amperage
Is the current (quantity of electrons) that can flow through wire or cable.
Voltage
The electrical force needed to drive a current between two points, similar to the water pressure needed to flow water through garden hose.
Wattage

The amount of electricity used.

1 Watt = 1 Volt x 1 Amp.

Electrical Wire Colour Code

The colour of a wire tells you the best use for it. White wires are usually neutral wires, green or bare wires are ground wires, and any other color is usually hot (carrying a current). In existing wiring jobs, white wires may also be marked with black or red to indicate that it’s now a hot wire.

White

Typically considered neutral. It can sometimes be used as a hot lead in certain situations, such as switch loops.

Green and Bare Copper

These are ground wires and when installed correctly, do not carry any current.

Black

Hot wire for switches and outlets.

Red

Hot wire for switch legs and hardwired smoke detectors.

Blue and Yellow

Hot wire that is pulled through a conduit. 

Understanding Wire Labels

The information printed on the side of the wire gives you everything you need to know about the wire, from the sheathing to the material used and gauge.

Materials CU means it’s a copper wire, the most common type. An alternative is aluminum wire, but it degrades more quickly and isn’t widely used inside of homes.
Maximum Voltage Rating A number that indicates the maximum voltage the wire can safely carry.
Gauge
The most common gauges of wire are 10, 12 and 14. The larger the gauge the smaller the wire. If your project calls for a long run of wire, increase the gauge to ensure enough electricity can flow through.

Main Types of Electrical Wires by Application

A NMD90 wire stripped to show the contents under the wrap.

Building Wires

  • “NM” stands for non-metallic sheathed, which refers to the flexible, typically PVC sheathing surrounding the cable.
  • “D” refers to dry location, this cable is for indoor use only.
  • “90” indicates a heat rating of 90-degrees Celsius, ensuring that its interior wires can operate at certain levels without overheating. 
  • This is the most common form of indoor residential electrical wiring.
  • Inside the sheathing are at least two thermoplastic insulated wires of the same gauge, though different cables can have different gauges.
  • For indoor use only, in spaces free from moisture and away from any heat sources. Do not bury or run outside of a wall.
  • Best used behind walls and ceilings and inside floor cavities.
A underground wire stripped to show the contents under the wrap.

Underground Wires

  • “NM” stands for non-metallic sheathed.
  • “WU” refers to being rated for wet or damp and underground installation. 
  • Looks similar to NMD90 cable but the wires are embedded as a group in solid thermoplastic (rather than individually encased in flexible thermoplastic).
  • Rated for use at conductor temperatures not exceeding 60 degrees Celsius.
  • Like NMD90 cable, NMWU cable comes in a variety of gauges to meet all electrical code requirements. It is labeled with the same information carried on NMD90 cable, plus the designation NMWU.
An armoured wire stripped to show the contents under the wrap.

Armoured Cables

  • “AC” means armored cable. Also referred to as “BX.” 
  • Consists of insulated hot and neutral wires and a bare bonding wire, all wrapped in paper. 
  • Wire enclosed in metal sheathing that acts as the grounding conductor. 
  • Relatively expensive and difficult to work with. Often found in older homes but not used in new builds. 
  • For indoor use only.
A portable wire stripped to show the contents under the wrap.

Portable Cords

  • Multiple jacket types provide a selection of different combinations featuring oil and water resistance, flexibility and abrasion resistance.
  • Often put to use in custom applications for heavy tools, battery chargers, portable lights, welding leads, marine dockside power, power extensions and even mining applications.
A bare copper wire, tightly wound.

Bare Copper Wires

  • Uncoated copper wire.
  • The most common wire used for grounding.
Low-voltage wire is stripped to show the copper underneath.

Low Voltage Wires

  • Usually rated for 50 volts or less.
  • Common low voltages are 12v, 24v and 48v.

Home Electronics & Communication Cables

An ethernet cable showing both ends.

Phone & Data Cables

  • Common types are phone cable, HDMI, ethernet and speaker cable.
  • Used to connect devices and carry signal to and from electrical devices.
A coaxial cable stripped to show the inside copper.

Coaxial Cables

  • Commonly used to transmit and receive television signals and connect video equipment.

Recommended Wattage Load per Gauge

Gauge

Recommended 80% Wattage Load

Max Wattage Load

Recommended For

14

1440 watts (120 volts)

1800 watts (120 volts)

Common residential wiring: Light fixtures, household receptacles.

12

1920 watts (120 volts), 3840 watts (240 volts)

2400 watts (120 volts), 4800 watts (240 volts)

Common residential wiring: Light fixtures, household receptacles, small appliances.

10

2880 watts (120 volts), 5760 watts (240 volts)

3600 watts (120 volts), 7200 watts (240 volts)

Large household appliances: Window air conditioner units, clothes dryers.

8

7680 watts (240 volts)

9600 watts (240 volts)

Large household appliances: Electric ranges, central air conditioning.

6

10560 watts (240 volts)

13200 watts (240 volts)

Large household appliances: Central air conditioning, electric furnace.

Recommended 80% Wattage Load 1440 watts (120 volts)
Max Wattage Load

1800 watts (120 volts)

Recommended For Common residential wiring: Light fixtures, household receptacles.
Recommended 80% Wattage Load 1920 watts (120 volts), 3840 watts (240 volts)
Max Wattage Load 2400 watts (120 volts), 4800 watts (240 volts)
Recommended For Common residential wiring: Light fixtures, household receptacles, small appliances.

 

Recommended 80% Wattage Load 2880 watts (120 volts), 5760 watts (240 volts)
Max Wattage Load 3600 watts (120 volts), 7200 watts (240 volts)
Recommended For Large household appliances: Window air conditioner units, clothes dryers.
Recommended 80% Wattage Load 7680 watts (240 volts)
Max Wattage Load 9600 watts (240 volts)
Recommended For Large household appliances: Electric ranges, central air conditioning.
Recommended 80% Wattage Load 10560 watts (240 volts)
Max Wattage Load 13200 watts (240 volts)
Recommended For Large household appliances: Central air conditioning, electric furnace.

Safety Information

Electrical work should always be done by a professional. Always be sure to shut down your power, at the breaker panel, before attempting any electrical project. If you need help, our Home Services installers will be glad to assist.

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