Color codes matter, and they’ve been around for longer than you realize. This article from The Institution of Engineering and Technology has a picture of wiring rules from IEE’s 7th Edition (1916).
That picture is eye-opening because it identifies red as the positive line and black as the negative. Yellow and white are neutral. But how does that compare to contemporary color codes? Where do brown and blue fit in this equation? Consider the following:
1). Wiring Codes
It should be noted that wiring codes are constantly changing. Your country may associate ‘Red’ with the live wire, but other regions on other continents are not obligated to follow that scheme. Whenever you migrate to a new location, make it a point to consult the local regulatory body.
Locate a handbook and determine whether their color codes match the scheme you know. Why? Because manufacturers use colors to specify the role each wire plays. Therefore, if you get the color codes wrong, you run the risk of wiring your home, application, or appliance poorly.
2). Red/Blue/White
Many laypeople can identify positive and negative wires with relative ease. This is because they are accustomed to this convention:
- Red – Positive
- Black – Negative
- White – Ground
This standard applies to DC devices such as solar cells and batteries. Some DC applications have two black wires. In that case, a white stripe will set a black wire apart as the negative line. The positive wire is plain black. What about AC power? It also follows a familiar scheme:
- Black – Positive
- Red – Positive
- White – Neutral
- Green – Ground
The red wire is the phase 2 line. You should also look for a blue phase 3 wire. The AC power color scheme is widespread, and the colors mean what you expect:
- The black or red wire brings the current to the application. It is the most dangerous because it is always energized.
- The white wire is equally dangerous because it takes the current back to the source.
- The ground is only dangerous during a surge when it provides a path of least resistance for the excess electricity.
The number of hot wires in your system will depend on the phase (Single or Three-Phase). Some applications require multiple live cables. Don’t forget that color schemes change with the location. For instance:
- Europe uses brown for ‘Line, Single Phase’ and ‘Line, 3-Phase.’ Black is the old color. Neutral is blue.
- The UK uses brown for ‘Line, Single Phase’ and ‘Line, 3-Phase.’ Red is the old color. Here, blue is also neutral.
- The US uses black or red for ‘Line, Single Phase’ and black for ‘Line 3-Phase.’ The neutral is white.
- Canada uses black or red for ‘Line, Single Phase’ and red for ‘Line 3-Phase.’ The neutral is white.
All-About-Circuits has a more comprehensive collection of color codes. As you can see, some of the differences are minor. However, they still matter. Don’t proceed without consulting the local handbook.
3). Brown/Blue
If you’ve encountered blue and brown wires for the first time and don’t know what they mean, there’s a way of making sense of their polarities.
The brown wire is live, while the blue wire is neutral.
Interestingly, the ground wire is still green or yellow. Although, don’t be surprised if yours is bare. How does this help you?
In the black/white/green color scheme, the black wire is live and positive. Therefore, you can safely assign a positive polarity to the brown (Live) wire in your circuit. What about blue? RS calls this color ‘Negative.’ You will find it at the end of the circuit.
You need a ground connection to prevent the appliance’s energized metal casing from shocking you when a short circuit occurs.
Again, the wiring code matters. Some wiring standards include blue but not brown. Consider the guide Mr. Electric has published. It mentions a black wire that brings electricity to the switches and outlets and a red wire in 220V circuits that acts as a secondary hot line.
Blue wires are live as well. You find them in conduits. They may appear in three and four-way switches as traveler wires. Don’t be surprised if the live wire takes on a yellow color.
White and gray are neutral, while the green electrical line is the ground. By the time you read this, the scheme above may have changed.
According to Household Quotes, brown and blue became the live and neutral wires in the UK in 2006. Before 2006, ‘Live’ was ‘Red’ while ‘Neutral’ was ‘Black.’ Therefore, don’t assume that brown and blue are still ‘Live’ and ‘Neutral’ in your country today.
Try to stay abreast of changes in your local electrical code. If you have doubts, talk to a local electrician. They have the expertise to interpret and apply the updates in the electrical code.
4). Wiring Brown/Blue Connections
- The brown wire runs to the black wire on your property. Both lines are live and energized in an active circuit. This makes them highly dangerous.
- The blue wire runs to the white wire. Both lines are neutral and negative. They carry the current back to the source.
Experts will encourage you to test the wires before taking action, especially if you don’t recognize some of the colors. A voltage tester will light up if you place its metal tip on a live wire’s exposed end. If the wire is neutral, the tester won’t light up. A multimeter will provide more concrete results:
- Set the multimeter to the highest AC voltage range.
- The red probe runs to the wire’s exposed end, while the black probe connects to any metal surface.
- A 0V reading points to a neutral wire. A live wire will show the same voltage as the socket.
If you need clarification, the below video will show you how to test the wires and interpret the readings.
Apply the necessary precautions before handling the live wires, such as de-energizing the circuit and wearing rubber gloves.