How To Identify Switch Live Wire?

How To Identify Switch Live Wire? |

Sometimes when changing a light fitting and after removing the old one. You find yourself lost between all these wires and do not know to wire up the new fitting. The first thing to do is to identify every wire, and the most important wire to identify is the live one. So, how to identify switch live wire?

How To Identify Switch Live Wire?

Even though you may be dealing with a low voltage circuit, you need always to be careful when dealing with electricity. Always try to be safe and stick to the safety guidelines. You can identify any switch live wire through some easy steps, and they are:

1- Isolate The Supplies

The first thing before getting to work is to make sure that everybody knows you’re going to work on a certain circuit. You can either label the switches of the circuit or isolate its supplies. The next thing is to shut down everything connected to electricity through the house, for example, the watching machine or the computer.

Switching everything off avoids any damage that any unexpected power surge can do. After knowing that it’s safe to work, grab your equipment and safety tools.

2- Unscrew The Switch Cover

Get your screwdriver, then start unscrewing the switch cover. After uncovering the switch, you will see all wires and where they are coming from. A circuit could have many breakers; for example, you could have a breaker for upstairs fitting and another for downstairs. Usually, circuits can have up to 1200 watts of breakers.

Therefore, if you unscrewed a light fitting on the upstairs circuit and cannot get it back working, this can cause all of your upstairs fittings to stop working.

3- Prepare Your Test Meter

To start identifying the live wire, you will need a test meter. It doesn’t have to be expensive; you can use any test meter you have. The next thing to do is to put your test meter on the bleep test, so you would know when you touch the right wire. You can touch the two arms together to test that it’s working, and there should be no resistance.

4- Start Testing The Wires

Usually, the live wire is the black-colored one, or sometimes it can be a red-colored wire. So, using the test meter clips, start testing the wire, and if it bleeps, it’s the right one. An important fact when trying to identify a live wire, the wire always has brown stripes on it. After knowing the live wire, you can put a label on it to help you in any future electrical tasks.

Related Readings:

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How To Wire a Single-Pole Switch in 3 Ways?

The single-pole switch is the most simple and common, and it consists of two terminals and one ground connection. Inside the switch, there’s a track that controls the electricity passage. You can either turn the circuit on or off; the toggle is the button or the switch you press. So, you can wire this switch in three different ways, and they are:

1- The First Method

The methods differ from each other in the order of the components. In this method, the switch will be the first thing in the circuit. So through these steps, you can start:

  1. The Black Live Wire
    Before doing anything, turn the power off next, then connect the black live wire to the switch’s bottom terminal. Then grab another wire that will be a live wire, and connect to the appliance you want to connect to the switch.
  2. The White Neutral Wire 
    In the switch’s box, there should be two wire nuts; grab a white-colored wire and connect it to one of the nuts in the box. And this will be the neutral wire. Then, as we did before, connect another white wire from the nut to the appliance that needs to be connected to the switch.
  3. The Ground Wire
    There should be an empty wire nut in the switch’s box; grab a ground wire and then connect it to the nut. Then, connect another ground wire from the ground nut to the switch ground terminal. And the last step, connect a ground wire from the appliance to the ground nut.
  4. Give it a Test
    Power on the circuit again, then turn the switch on. Now, the electricity can pass from the source to the appliance perfectly.

2- The Second Method

In this method, we will change the arrangement of the circuit. Instead of having the switch as the first component, we will put the appliance first in the circuit. You can follow this method through these steps:

  1. The Black Live Wire
    Like the method before, turn off the power before starting to work. Unlike the previous method, the wire nuts here will be in the appliance box. For example, if you’re using a lamp, the wire nuts will be in the ceiling box. Grab a black-colored live wire and connect it to the wire nut.
    Then, connect a black-colored live wire from the appliance to the top terminal in the switch.
  2. The White Neutral Wire
    Grab a white-colored neutral wire and connect it to the appliance. Next, grab another white-colored from the same wire nut of the black-colored wire and connect it to the bottom terminal in the switch. However, due to the arrangement of the components in this method, the white wire will act as the live wire.
    So, it would be best to mark it with a label or electrical tape; to warn anyone about it.
  3. The Ground Wire
    This is an important step; first, grab a ground wire and connect it to the empty nut, then connect the nut using two ground wires, one to the switch ground terminal and the other to the appliance. For example, if you’re using a lamp and a ceiling box, there should be a ground wire connected to the ceiling box.
  4. Give it a Test
    Turn on the power and connect the circuit; as you can notice, the electricity can pass properly from the switch to the appliance. You can control the circuit by toggling the switch on and off.

3- The Third Method

This method is nearly identical to the previous method except that, instead of having the white wire carry a current to the switch. We use a red-colored wire to be the second live wire in the circuit. In addition, to make the white-colored wire work properly, you will need to use another wire nut in the switch box.

So, the circuit works the same as the previous one, and you can use the switch to turn it off and on.

Here’s a detailed video on how to do it:

What Are the Types of Wire Lighting Systems?

Lighting systems can differ from one house to another, and you can often see both of them. But how does knowing which system is which will benefit you?. Knowing which system you have and understanding how it works can help you know which products can work on your system. For example, if you have a 2-wire system, you can install relays.

The wire lighting system has two main types, and they are:

2-Wire System

It’s the most used system in Europe, and you can find it in every house, especially if you live in the UK or Nordic regions. If you saw the 2-wire system, you might get confused. Because despite what it says in the name, the system consists of 3 wires:

  • The live wire or the brown-colored wire is responsible for carrying the current to the switch.
  • The switched wire or the blue-colored wire is responsible for carrying the current to the appliance or the light. So, it’s never liver when the switch is turned off, and that’s why it’s called the switched wire. The switched wire has brown sleeves or strips on it for safety purposes to warn that it’s a live wire.
  • The ground wire or the one with yellow/green strips, its main job is protection and disperse any power surge during a short circuit.

So, the system is called a 2-wire system due to having only 2 main wires, the hot/live wire, and the switched wire.

3-Wire System

The 3-wire system is not common as the 2-wire system. It mainly consists of 3 main wires the live wire, the neutral wire, and the switched wire. The neutral wire is used to complete the circuit by carrying back the current to the source. Other than that, the 3-wire system doesn’t differ that much from the 2-wire one.

How To Know Which System Do You Have?

It would be best to assume that you have the 2-wire lighting system, as it is more common, especially if you’re a UK resident or your house is older than 3-5 years. However, you can know by checking some points in your house:

  • All the wires must be connected to the switch
  • All the wires have brown stripes on them

If the two previous points are true, you have a 2-wire system. Other than that, you have a 3-wire system.

How To Know Which Products Will Work With Your System?

It’s very simple to know which product will work properly with your system. After knowing which system you have, search for a label on the product. It should have an image of two colored wires and a number beside them, either the number 2 or 3. The number refers to the system suitable for the product.


To sum up, identifying the switch live wire is a simple job if you have the needed equipment. But always remember, electricity can be fatal and cause many injuries. So, before working, make sure the power is off and leave a notice to everyone to not turn it on again until you finish. Be cautious and stick to safety guidelines.

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