To determine line and load wires, you have to find the black and red wires. In most cases, black can be the line wire and the red wire is the load. Because various nations use different colors, it might be difficult to distinguish between the line and load wire colors in an electric circuit.
The quickest approach to determine the line/hot and load wires is to look at the insulation colors. There are, however, methods for recognizing the wires in the house.

How to Determine Line and Load Wires?
The majority of electric cables are insulated to protect consumers from electric shock. Each color on the electric wire has a purpose but may be used interchangeably. The colors include black, red, yellow, gray, bare copper, brown, blue, white, and green with yellow stripes.
Determine Line/Load Wires by Color
White and gray wires are neutral. Green with yellow stripes, green and copper wires are ground wires. Black might be the line/upstream cable or load/downstream wire. And red or black are load/downstream wires. Travelers are either white or black.
By learning the colors used in your nation, you’ll be able to tell which is line wire/hot and which is load wire. Different nations use different color codes for wiring.
Determine Line/Load Wires by Its Position
Line/incoming wires are always attached from the bottom to the electrical panel, whereas load cables are connected from the top. You can tell the difference between the line and load wires in the electrical panel by looking at the position of the connected wire on the panel box.
Wires on the panel box can help you a lot, and if you can’t find them, get help from a friend or an experienced electrician who will be able to help you handle the problem securely.
Determine Line/Load Wires by Voltage Tester
Volt stick/pen measures voltage without touching bare copper wire; use a voltage pen to test every wire linked to the switch. Consider other persons in the house when testing each line, and never leave bare wires unsecured in any case.
If the pen tester lights red, the wire is line wire; if the pen does not flash at all, the wire is load wire. A volt stick is a useful tool for checking the current-carrying wire without having to undo the cable’s connection to the meter box.
Determine Line/Load Wires by Digital Multimeter
A multimeter is a device that measures the electric values, voltages, resistance, and current in an electric circuit. To identify the line wire and load wire in your meter or socket, turn your multimeter knob to AC voltage and read 200 volts. The black probe reads COM, while the red probe points to V. (voltage).
Connect the multimeter’s insulated terminals to the terminals of wires connected to the switch. If it displays 120 volts or above, it is the line and load wire in your meter box or switches. Using a multimeter appropriately can alleviate the problem of recognizing the line wires and load wires, which might be difficult to identify.
How to Differentiate Between Line and Load Wires
A line is a wire that connects a current source to a switch. It is located upstream of the switched device. The line is constantly hot. On the other hand, load is the wire that connects the switch to the device. If the switch is closed, the load will be hot.
Consider a spigot and hose. The pipe exiting the home, like the line wire, is always under pressure. The spigot serves as the switch, while the hose serves as the load. When you turn the handle, you get water pressure (voltage) in the hose, but when you turn the handle off, the hose stops transporting water.
Precautions
When dealing with electricity, avoid working on wet flooring. Wear shoes with rubber soles since they conduct zero electricity. Metallic ladders should be avoided since they carry electricity well. Rubber-insulated tools are always the best to use. Also, make sure not to overload the electrical outlet.
Use only approved and recommended light bulbs, wiring, and equipment. Never work with exposed electric lines. While working, avoid dangling cables over your head. You should know about electrical repairing; if you are not trained as an electrician, seek the services of a certified electrician.
If Line and Load Get Mixed Up
A ground fault (radio in the tub) will not trip the GFCI (Ground-Fault Circuit Interrupters) if the load and line wiring are mixed up. This occurs when the hot and neutral wires are reversed at an outlet or upstream from an outlet. Reversed polarity can provide a shock risk, although it’s typically a simple fix.
Is the line a load or common?
Remember that one side of the three-way common is the line side and the other is the load side or switch leg. Carriers are the two wires that link the three-way switches.
Conclusion
Color code is usually not the most effective way to determine the line and load wires. It is recommended to follow the other methods. Also, make sure to obey the safety precautions before you get involved in these types of operations.
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