You can’t proceed with a wiring project without learning to interpret color codes. The color tells you what a wire does. Blue is no different. However, determining its function means looking at the color scheme your country uses.
Is Blue Wire Positive or Negative?
IEC AC Power
- Blue – Neutral
- Green/Yellow – Protective Earth
- Brown – Line, Single Phase (L)
- Brown – Line, 3-Phase (L1)
- Black – Line, 3-Phase (L2)
- Grey – Line, 3-Phase (L3)
UK AC Power
- Blue – Neutral
- Green/Yellow – Protective Earth
- Brown – Line, Single Phase (L)
- Brown – Line, 3-Phase (L1)
- Black – Line, 3-Phase (L2)
- Grey – Line, 3-Phase (L3)
US AC Power
- Blue – Line, 3-Phase (L3)
- Green/Yellow – Protective Ground
- Black or Red – Line, Single Phase (L)
- Black – Line, 3-Phase (L1)
- Red – Line, 3-Phase (L2)
- White – Neutral
Canada AC Power
- Blue – Line 3-Phase
- Green/Yellow – Protective Ground
- White – Neutral
- Black or Red – Line, Single Phase (L)
- Red – Line, 3-Phase (L1)
- Black – Line, 3-Phase (L2)
IEC DC Power (2-Wire Earthed DC Power)
- Blue – Negative of a negative earthed circuit
- Blue – Positive of a positive earthed circuit
- Grey – Negative of a positive earthed circuit
- Brown – Positive of a negative earthed circuit
IEC DC Power (3-Wire Earthed DC Power)
- Blue – Mid-Wire
- Brown – Positive
- Grey – Negative
As you can see, color codes will vary with each location. Additionally, the system changes the meaning of each color. For instance, blue is the neutral line in AC power systems in most European countries. This is also true for AC power systems in the UK.
But in the United States, AC systems use the white wire as the neutral. Blue is ‘Line, 3-Phase.’ These color schemes don’t mention the polarity until you shift to DC power circuits. But in IEC DC power circuits, you can see that blue can be positive or negative.
DC power circuits in the US don’t feature a blue wire. They use white instead of blue. This tells you that a blue wire’s meaning depends on the setting. Consider the following:
1). Electrical Socket
Electrical sockets have live, neutral, and ground wires. While many countries use red or black for the live wire, don’t be surprised if you see brown. The ground conductor is green or bare. Blue is neutral. The polarity doesn’t matter in this situation. In other words, blue is neither positive nor negative.
2). Audio Cable
The polarity doesn’t matter because you’re still dealing with an AC circuit. Therefore, you can’t separate these wires into a positive and negative side.
3). Plug
An electrical plug is similar to an electrical socket. You have a live, neutral, and ground wire. The blue wire is neutral. It is neither positive nor negative.
4). Ceiling Fan
You see the blue wire in a ceiling fan when the kit includes a light fixture. The blue wire will bring power to the light fixture. If you configure the ceiling fan without connecting the blue conductor to a power source, the light fixture won’t work. You can ignore the blue line if you don’t want the light fixture to work. But you should cap the blue wire to be on the safe side.
In this case, the blue wire is the negative line. Black is positive. The blue wire runs to the positive terminal. Black connects to the negative terminal.
5). Speaker Wire
Different Methods To Find Whether Blue Wire Is Positive Or Negative
- Color Code
Color codes are the most straightforward solution. If you know the color scheme your local authorities use, you can predict the blue line’s polarity. However, this method is tricky because you can’t prove that everyone who came before you applied the same color scheme.
This is particularly important when you perform repairs on a pre-existing circuit. Unless you consult the contractor that installed the wires, relying on color codes forces you to tolerate a certain amount of risk.
- Multimeter
A multimeter is the only reliable solution to this problem because it measures the wire’s polarity directly. Connect the multimeter’s probes to the wires. Use the small alligator clip to secure the connections.
Check the readings. What polarity do you see? The multimeter will show a negative or positive number.
- Ribbing
Some manufacturers use physical features to show the polarity. For instance, if you have two blue wires in an extension cord, the negative wire is ribbed or grooved.
What Color Wire Does Blue Go To?
The blue wire is usually the neutral wire. A neutral blue wire will connect to the white line or the neutral terminal, depending on the setting.
Let the manual guide your actions if you see the blue wire in an electronic device. It will tell you what the blue wire means and how to use it. Don’t expect the device’s manufacturer to follow conventional color schemes.
In other words, you can’t expect the blue wire to perform the same function in every situation. If the manual and local regulations have given the blue wire different polarities, follow the manual. The manufacturer knows more than the local authorities regarding their electronic device.
What Happens if You Connect Wrong Wire To Blue Wire?
- Neutral To Hot
Connecting the neutral to the live wire will cause a short circuit. You will observe sparks at the point where the wires make contact. A fire may start if the sparks ignite an object in the vicinity. This experiment may blow a fuse or trip a breaker, depending on your setup.
In many cases, the neutral and live conductors touch because of a fault in the appliance. It is rare for people to connect these two lines intentionally.
- Neutral To Ground
The neutral wire carries a current back to the panel. The ground is the opposite. It doesn’t have power. It only becomes hot when a surge occurs. The ground wire takes the excess charge to the earth.
Connecting the neutral to the ground makes the ground hot. This mistake will initially go unnoticed because nothing tangible will happen. However, you can’t forget the function the neutral wire plays.
The neutral wire provides the only path back to the panel. Connecting the neutral line to the ground creates two return paths to the panel. This is problematic because it compromises the functions of the RCD.
If you have GFCI protection, the resulting voltage difference will cause nuisance tripping because the GFCI has detected an imbalance in the incoming and outgoing current.
This assumes that your blue wire is neutral. Again, you should check the color scheme to confirm. The observations you make will change if the blue line in your region is ground or live. Don’t count on the breaker or fuse to protect you every time. Hire a contractor to identify and undo your wiring mistakes before it’s too late.
Related post: