Load wire and line wire (what's the difference?)
Content
In houses, two lines come out of the meter: active and neutral wires. The neutral wire is always connected to earth and the live wire goes into the fuse box (SFU). When the main switch is turned on, an electrical potential equal to zero at ground is applied to the load wire and the load draws power.
It is not always easy to distinguish line wires from load wires. As an experienced electrical engineer, I will help you understand the difference between load and line wires using a few simple tricks. Knowing this, you can avoid reversing the polarity of the load and line wires, which can lead to electric shock.
You can distinguish a load wire from a line wire in a circuit by considering the following features:
- Wire placement
- Wire codes
- Wire size
- Measurement of voltage (V) and current (A)
Below we dig deeper.
Fundamentals of Load and Line (Electrical) Wires
It is very important to know the terms "line" and "load" in relation to one device.
Line Wire
As soon as electricity arrives at the facility, the line connections transfer it from the utility grid to the electrical panel. The power is then directed to the devices in the circuit through the load connections. In this case, the load wires from the panel serve as the device's line wires.
Load wire
A device load wire is the line wire of another device downstream. When testing a circuit, this can cause problems; therefore, there are several indicators to distinguish live wiring from live wiring.
What happens when you reverse polarity?
Thus, each device in the circuit must have line and load indicators to ensure proper connection. However, in some devices, the change to these connections may be minor.
Single pole, single position switch works great even with reverse connection. However, since the terminal connections in multi-position switches are directional, they will not work effectively if they are reversed.
In either case, reversing polarity creates the risk of electric shock, short circuit, or fire. This is because after a polarity reversal, the device will remain energized even if the switch is turned off.
Load compared to line wires
Several conventions have been adopted in the industry to distinguish between line and load wires to prevent unintended consequences of polarity reversal in electrical wiring. Here are some of the parameters used to distinguish wires:
1. Wire placement
The connection of line wires to the electrical panel or switch is usually made from below. The load wires enter from the top. In addition, these line and load connection points are labeled to indicate what type of wire they are intended for.
2. Color codes
Color codes are used in electrical connections to identify different types of wires. Similarly, these codes vary by country. In some countries, black indicates line/uplink wires and red indicates load wires. Moreover, in some countries the screws on each terminal are color-coded. As a result, mastering region-specific color coding is required.
3. Wire size
Because devices typically reduce voltage or current, the power carried over the line wire exceeds that of the load wire. Line wires are usually larger than load wires. This is true if the power difference is large. The absence of a change in voltage or current in devices such as overloads or protections makes this method ineffective.
4. Measurement of power characteristics
Because the electrical power at the device's output is less than its input, measuring the voltage or current at these ends can help distinguish between line and load wires. In addition, non-intrusive methods for measuring these parameters are provided by devices such as the voltmeter/pen and digital multimeter. When in contact with a terminal screw or bare wire, a neon screwdriver can check these parameters.
GFCI applications
The dangers of reversing line and load connections have been discussed in previous sections of this article.
If you suspect a polarity reversal, turn off the power to the room or outlet immediately. Then, using a standard outlet tester and a voltage chart, verify that the outlet is wired correctly. If the wiring is not connected correctly, a simple wire switch solves the problem. Unfortunately, this is a reactive approach that leaves equipment and people vulnerable to reverse polarity hazards. Now the ground fault circuit breaker (GFCI) outlets come into play:
How GFCI works
Unlike a fuse that protects devices, the GFCI is built into the outlet and eliminates the risk of electric shock. It constantly monitors the current flow and interrupts it whenever there is a spike. As a result, it protects against any ongoing anomalies.
To protect this outlet and other outlets downstream of the circuit, a GFCI connection is required to both the line and load terminals. Reverse polarity can also occur in GFCI receptacles. As a result, proper connection of the line to the load on that outlet is essential to the safety of all outlets downstream of the electrical circuit.
Take a look at some of our articles below.
- Which wire goes to the brass screw
- What color is the load wire
- How to plug electrical wires
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