Our Home DIY Guide: How To Install A Dimmer Switch

Dimmer switches aren’t just a trendy way to control the lighting in your home, it’s also a great way to be more energy efficient and use light to enhance your interior style. With LEDs becoming more common and fashionable these days. Installing a simple dimmer switch can be a daunting task, and we would be the first to say if you have any fears in dealing with live electrics to hire a professional electrician, but for those of you keen to learn more DIY skills and save money, this process is quite easy, if you have the right equipment and know the dos and donts,it can be an easy thing to do yourself when it comes to installing this alternative type of stylish light switch.


  • Dimmer Switch

  • Cutting & Needle Nose Pliers

  • Wire Strippers

  • Slotted & Phillips Head Screwdriver

  • Voltage Tester

  • Outlet Wall Plates

  • Wire Connector Nuts

  • Electrical Tape


Check the UK Government Regulations for electrical safety in the home, as these are designed to help and ensure you and your home are not at risk of electrical shocks or fire. Most small DIY tasks do not legally require notifying building authorties but, if in doubt, contact a local qualified electrician who is registered with a Part P Self Certificate Scheme to handle the job, otherwise ensure you are aware and suitably trained to handle any electrical work before you start. These guidelines also suggest height and location of sockets and switches and other mandatory criteria, and not adhering to these guidelines could be dangerous and render your home insurance invalid. On a superficial front, it could make your interiors end up looking incredibly amateur and potentially devalue your property in the future.


A dimmer switch works by regulating the amount of current which flows through the electrical circuit. Most dimmers are designed to fit a standard wall box opening, which makes it easy to replace the switch for any incandescent or halogen light. A ‘dial’ type dimmer is the simplest and usually the cheapest style of dimmer you can buy, but it is worth looking at high end alternatives out there like remote control dimmer units and can be found through designers such as Buster + Punch, Dowsing & Reynolds, or B&Q.


There are two types of dimmer:

Standard single-pole - A single switch controls the light.

A Three-Way Switch - A light controlled with two switches, which will need a three-way dimmer and a three-way switch, letting you dim from one location and turn the lights on and off from another.


If you’re using LED bulbs, these bulbs themselves need to be specifically marked as ‘dimmable’ otherwise you will experience flickering when using a dimmer switch. Also ensure you use a specific type of dimmer switch for LED lights, these are called a Trailing Edge dimmer switches. These are slightly more expensive than regular dimmers, but fitting them is exactly the same.

LED Ceiling Chandelier

LED Ceiling Chandelier


  1. Cut the power to the switch at your circuit breaker box or fuse box, and confirm power is off by flipping the switch on and off.

  2. Ordinary dimmer switches are not intended for use with most fluorescent lights, so only use CFLs (compact florescent energy saving bulbs) labeled as ‘dimmable’.

  3. Do not use an ordinary dimmer switch with a ceiling fan as the current fluctuations can burn out the motor.


  1. Remove the existing wall plate and the screws mounting the switch to your wall box and gently pull the switch away from the wall - if you see a bundle of white wires in the back you can leave these in place.

  2. Do not touch any of the wires until you’ve confirmed they aren’t carrying electrical current. you can do these by using a voltage tester. If it detects voltage you need to switch off the appropriate circuit breaker or remove the appropriate fuse and test the circuit again.

  3. A red and black wire are connected to the switch, both of these are the live wires when the circuit is reconnected. With a three-way switch, one wire will be connected to a screw that is colored differently or labeled ‘Common’, this is different from the wire connected to the green screw - the ground wire. Tag the common wire with a piece of electrical tape to identify it when wiring the new dimmer.

  4. Disconnect all wires from the old switch.


Standard Single-Pole Dimmer

  1. If the house wires are bent, use a wire stripper to cut off the twisted ends. Remove 2cm of casing from the end of the house wires if needed.

  2. Connect the ground wire from your dimmer to a green or bare copper wire in the wall box by twisting the ends together clockwise and capping them using a wire connector nut.

  3. Connect each dimmer wire to a house wire by gripping the wire ends with a pair of pliers and twisting them together. The wires from the dimmer will typically be black. The two house wires may be black, red, or white with black marking. Tighten a wire nut over each pair of wire ends. If there is bare wire exposed, unscrew the wire connector, remove the wires, trim the ends of the wires with your wire cutter and then re-cap the wires.

Three-Way Switch

  1. If the house wires are bent, use a wire stripper to cut off the twisted ends. Remove 2cm of casing from the end of the house wires and the dimmer switch wires, if needed.

  2. Connect the ground wire from your dimmer to a green or bare copper wire in the wall box. Twist the ends together clockwise and cap them using a wire connector nut.

  3. Connect the black dimmer wire to your tagged common wire and remove the electrical tape.

  4. Connect the two remaining dimmer wires (called traveler wires) separately to each remaining wire in your wall box.

  5. Use your screwdriver to mount the dimmer to the wall with the provided screws.


  1. Carefully tuck the wires back into the electrical box, and tighten the screws holding the dimmer to the electrical box.

  2. If you are installing a dimmer that has a removable knob, remove it from the dimmer by gently pulling outward before attaching the wall plate.

  3. If the dimmer has a separate wall plate, tighten the mounting screws that hold the wall plate to the switch. If you are using a wall plate with a ‘screwless’ design, screw the wall plate adapter to the dimmer, and then carefully snap the wall plate onto the adapter.

  4. Turn the power back on at the breaker and test the dimmer.

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