What Is A Switch Loop & How Does It Work?


Electricity is fundamental to the modern household. It’s used to power your lights, heating, cooking and even recharge your cell phones and tablets. It’s easy to forget that electricity didn’t exist before about 1880.

Now it is in every part of your home and your life which is why it is important to understand how it works. You may not wish to adjust your home electrics and prefer to use a reputable electrical services firm. But, this doesn’t mean that you shouldn’t understand the basic operation.

What Is The Switch Loop?

The switch loop is an integral part of your home; another way of describing it is as a connection between your light and a switch, allowing you to turn it on and off at will without removing the bulb.

This loop can be used to create one switch or several switches; all operating the same light. In fact, there are a couple of different ways in which you can wire a switch loop depending on whether the live feed is going directly to the switch or to the light.

The switch loop works by turning a neutral wire into a live; this is why it is important to be aware of how it works; in case you ever expose the wires in your light fitting and assume only the brown wire is live.

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Creating The Switch Loop – Power To The Light First

The first stage is to identify the live wire coming from the light bulb.

You can then connect this to a neutral wire that runs to the light switch; the power doesn’t go to the bulb at this stage.

It is important to mark the neutral wire to ensure you know it is acting as a live one.

The neutral supply to the light should be connected as normal.

At the switch you will have power coming in via the neutral wire. This should be connected to the live in terminal on your switch. You can then connect the live wire of the cable between switch and bulb to the L1 connection on your switch. The other end of this should be connected to the live in on your light.

Finally you want to continue your neutral feed. This means running the fourth wire in your switch feed to the neutral terminal on your switch and the neutral in your light fitting. Your earth wires should be connected as normal.

The power has now been rerouted to the switch, allowing you to turn the light on and off whenever you need to.

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It is possible to add lights to this circuit. The live, neutral and earth for each of the lights simply connect to the cables entering the light fitting. This ensures the switch loop wiring is no disturbed and remains effective.

Switch Loop When Power Arrives At the Switch First

This is actually very similar to the above method. The key difference is in where the live power is coming from.

You may think that you can simply add the incoming power to the switch and send it out to the light, allowing the switch to control the light.

Fortunately this is possible, making this the easiest option but the most unlikely one that you’ll come across.

Adding Two Switches To A Loop

When you have a large room or you need to be able to turn a light on or off from up and downstairs then you need to add a second socket into your switch loop.

This is surprisingly easy to do; once you know how.

Assuming the power is arriving at the light you’ll need to run it to one of your switches via the neural cable; as described in the first example.

You can then attach the neutral cables together for the power in, both switches and the light.

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The next step is to run a cable between the L1 sockets on both switches. This connects them and allows both switches to work independently.

You can then run a cable from the power in on the second switch to the live connector on the light. Again, you should connect the neutral in from the mains onto the light and ensure this is connected to both sockets; this is why you’ll need a four core cable.

Don’t forget to mark the cables that are carrying power but aren’t the usual live color. This will ensure no one gets accidentally electrocuted.

As soon as you’re finished you can test the switches, you should be able to turn the light on and off from either switch.

Remember, electricity is dangerous; if you’ve not tried this before then at the least you should get your work checked by a professional before you start using your new switch on a regular basis.


  1. Can you add an example of how to add an an “always on” GFI Outlet to a pre-2011 Switch Loop that has power at the fixture and 1 switch? I have a bathroom that has an integrated light fixture and outlet today and would like an outlet on wall thats always powered.


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