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Replacing a Standard Light Switch with a Dimmer

By: Alan Cole - Updated: 12 Dec 2016 | comments*Discuss
Dimmer Dimmer Switch Remote Control

A dimmer switch is a perfect of way of becoming more energy efficient and providing attractive enhancement for decorations and furnishings around your home. On this page you will find information about fitting a basic dimmer switch onto an existing standard light switch. It’s a fairly easy DIY job but always make sure you are absolutely sure you know what you are doing before tackling any electrical DIY.

Dimmer Switches

Dimmer switches are plate switches allowing you to control the relative brightness of a light. The dimmer switch works by regulating the amount of current which flows through the circuit. The most basic and cheapest dimmer switch is a simple dial type. You simply turn it to click it on and then you can turn it further around to make the light brighter as required. You can also turn it backwards to make the light less bright and click it to turn it off. There are a good range of dimmer switches including more expensive types such as remote control dimmer switch units. Remote operation can take place from across the room with a similar control to a television.

Replacing a Standard Switch with a Dimmer

  • A standard switch is recognised as a one way switch which switches on or off.
  • First turn off the light circuit!
  • Remove the light switch face screws and pull out the face plate.
  • A red and black wire are connected to the switch. Both of these wires are live wires when the circuit is reconnected. 20px break
  • If you have a metal face plate for your switch there should be a green and yellow earth wire connected to a small terminal. This earth wire should be connected to the metal box in the wall - a pattress box. If the face plate is plastic there is no need for this short earth wire. The small screws are quickly undone to release the wires and they are then re-connected in the dimmer switch to the dimmer switch terminals.20px breakli4
  • If you have more than a red and black wire in your switch then it looks like you probably have two or three way lights. Two/three way switches are used where you want to turn a light on/off from different locations; e.g. at the ends of a hallway or at the bottom and top of the stairs. This is a more complicated job and it is advisable that you contact a suitably qualified electrician for this.20px break

Electrical Safety and Regulations

  • Always contact a suitably qualified person and check the latest Government regulations concerning electrical work, including the height and location of sockets and switches. lig2
  • Never underestimate the risk of danger from electricity including fatal electrical shocks and fire. Even if there is no smoke or flame there can still be a risk of fire. A spark can jump from electrical wires and start a fire.
  • Electricity kills and injures many people each year. In many cases people have died or been injured because they attempted electrical installations without being suitably qualified.
  • Always ensure you are suitably trained and qualified to carry out electrical work.
  • Always check you are fully conversant with the latest laws governing electrical work and installation in your locale.20px break

Changes on Electrical Safety England and Wales

From 1st January 2005 all electrical work in dwellings in England and Wales needed to comply with Part P building requirements and be carried out by persons who are competent. You need to check with the appropriate government authority to ensure you are up to date with this. The 2005 Building Regulations state any electrical installations must be carried out by a competent person. This goes beyond DIY knowledge about which wires go where.It is possible that an incorrect installation if not correctly certified in your home could render your insurance invalid.

All work that involves adding a new circuit to a property will need to be either notified to building control authorities who will then inspect the work or carried out by a competent person who is registered with a Part P Self Certificate Scheme.

Small jobs such as replacing a socket or switch on an existing circuit need not be notified to building control according to the 2005 introduced law, although there will be some exceptions for high risk areas such as kitchens, bathrooms.

While most jobs carried out by DIY folk will be small tasks that do not legally require being notified to building authorities or checked by suitably qualified persons they should still be checked out by a competent electrician for your own safety.

Ask The Experts

Never take any chances with electricity and jeopardize your safety. Always make sure you are up-to-date with the legality of any electrical work and are fully competent before tackling any electrical work. If in doubt contact a suitably qualified electrician or your local government department for advice.

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[Add a Comment]
Hi my husband tried to change a normal single switch to a single dimmer switch. It's a plastic box and so wired the red wire to C and the black wire to L1.However when turning the electric back on it blew a fuse, and the bulb came on and wouldn't turn off.We purchasd another dimmer and tried again, Same thing happened. WHY AND HOW HAS THIS HAPPENED?Thanks for any advice.....
SAL - 12-Dec-16 @ 8:39 AM
What about a 3 switch dimmer? Loads of wires here. Put all blue in L1 and all brown in common? Help!
keith - 14-Nov-12 @ 9:11 PM
@manonamission - if you want to replace a standard light switch with a dimmer it's simple.You just flick the breaker for the lighting circuit, check if the light is on and if not make an addition check for power using a mains tester.If there is no power then you just replace the two wires into the current switch into the dimmer.If it's a two way then it's slightly more complicated and you might want to seek some help.If the switch has a metal faceplate and an earth terminal make sure it is connected to the earth.The earth is green and yellow and should go to a terminal on the backbox.
sparky - 21-May-12 @ 5:18 PM
But this does not tell you how to install the dimmer!!No help at all.
manonamission - 13-Apr-12 @ 8:09 AM
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