A dual switch gives you the convenience of operating two lights or electrical equipment from the same location. Dual switches, sometimes called "double poles," make it easy for you to separately control the power delivered to different places through the same switch. For example, you might want to turn on the bathroom lights separately from the ceiling fan. Although installing a dual switch is not difficult, special safety precautions are essential to prevent injury.
Notes:
This article only describes how to install the switch itself, not for re-wiring two sources that you want to separate. If you are trying to separate two lamps that use the same connection instead of two separate sources, you will most likely need a trained electrician.
Step
Step 1. Disconnect the power to the room where you are working
Walk over to your circuit breaker and turn off the electricity in the room you are working in. Usually the circuits in that room are labeled, otherwise turn them off for your safety.
- The energy going to a switch should not be underestimated, and can cause serious damage if you come into direct contact
- You should still wear insulated gloves and shoes, with rubber soles to stay safe while working.
Step 2. Use a voltage detector to make sure no power is flowing
Touch the tool against the old switch connections and exposed wires to make sure no power is flowing. Some contractors tend to pile multiple room connections together while working, meaning that a bathroom near you that you thought was turned off might still be connected to the bedroom fuse.
- Touch the tip of the detector to the lamp joint in several places. If the detector light is on, it means that power is still flowing to the switch.
- Always check and double check to make sure no power is flowing to you while you are working. There is no such thing as being too careful when working with electricity.
Step 3. Remove the old switch bolt and pull it out of the wall
Remove the two screws and save it for later. Carefully pull out the connection, remove the switch from the wall-mounted switch box. There should be three to four wires connected to the switch screw, the wires are usually not labeled. You will have to find out the connection of each cable through a few tests for the next.
- Cable source is a current-carrying cable, which means it is always electrified. This cable conducts electric current to the switch, which then controls the electrical connections to lights, fans, and so on. These wires are generally red or black, although not always that color, and have a metal label or plate on the side.
- There will be two wires neutral connected to your electrical equipment, and each will be connected to your dual switch when you are done. This neutral wire is generally white, but not always that color.
- Cable grounding, which are generally green, yellow, or copper metal, and are connected to green screws, helping to protect your switch and housing from short circuits. Since this cable has not been legally required for some time, some switches may not be grounded.
Step 4. Take a picture of the current connection for future reference
If you are not an experienced electrician, take a quick picture to see where the wires are located. You can also draw a simple diagram. Mark each cable and the location of the connection.
Step 5. Remove the screws and pull out all the wires connected to the old switch
The wires are locked with screws, this part is generally called the "terminal". The screws are tightened to clamp the exposed parts of the wires together, thereby joining the circuit and powering the switch. To remove the cables, remove the screws and pull the cables off the screw rods.
- If you can keep the cable in its current shape it will make it easier to put it back in later.
- You should have three to four wires exposed coming out of the switch box.
Step 6. Carefully mark and disconnect the connected cables
This is likely why two lamps or electrical devices are connected to the same switch. For example, one of these wires might connect to your fan, and the other to the lamp. The two connected wires are wrapped or connected at the terminals, and are twisted on the same screw. It is likely that these two wires are your source wires, which will need to be plugged into different terminals later.
Part 1 of 2: Installing the Dual Switch
Step 1. Make sure none of the wires touch the metal
Now you have to do a test on the wires, and if they touch the metal switch box or metal wall you can cause a short circuit. Let the wires hang in the open air. You'll need to turn on the power to test the source cable if you're not sure.
Step 2. Turn the power back on to find the source cable if you don't know which cable is the source cable
If your wires aren't labeled yet, you'll need to know in advance which wire is supplying power to your switch. You also need to remember that the source wire is usually red or black and the neutral wire is usually white. To find the wires without looking at the color, turn the power back on at your job site. Using a voltage detector, touch the ends of each wire. The wire that makes the detector light is the source wire, because it is the wire that is now powered by electricity. Turn off the power before marking the cable.
Be careful with these cables when the power is on. Only touch these wires with a voltage detector and be sure to wear insulated gloves when working
Step 3. Determine which side of the switch is for the source wire and the other side is for the neutral wire
There is a metal square plate, which is usually found on a double switch which indicates the side to which the source cable will be attached. This is where you plug in your power tools. The other side is for the source cable and provides the switch with electrical power.
- Often, the source wire terminals (screws) are black or silver.
- The neutral side is usually copper in color.
- The green screw is usually for grounding.
Step 4. Bend the end of the cable until it bends and attach it to the bottom of the screw
We recommend that you bend the cable clockwise. This will make it easier for the cable to rotate as the screw is tightened. The order of the wiring is not a problem, but it is best to install the ground wire first.
- Only one cable is connected to each terminal.
- Make sure you remember to install the ground wire.
Step 5. Tighten the screws on the terminals so that the wires don't move anymore
It is recommended that the cables fit snugly against the terminals to ensure a good, strong connection. Tighten each screw to keep the cable from moving.
Step 6. Turn on the power again to test the connection
With both switches in the "off" position, turn the power back on and check each switch separately. The switch that has been installed will immediately turn on the connected electrical equipment.
Step 7. Turn off the power again and cover all terminals with electrical insulation
Wrap electrical insulation around each terminal, to protect against the risk of short circuits.
Step 8. Re-screw the new lamp connection
With the electrical power still in the off position, place the connection back into the wall and secure it with the screws provided. Turn on the power and celebrate! You have the new dual switch.
If this is a new connection, position the switch against the wall and mark the location of the screws on the wall with a pencil. Using a drill, make a hole at the mark you made in the wall and start drilling, screwing in the hole you just made
Part 2 of 2: Examination
Step 1. Turn off the power again before performing the inspection
If you are disconnecting or removing screws, for the sake of safety, turn off the power to the area where you are working first. Use a voltage detector to ensure that no electrical power is flowing to the switch before continuing to work
Make sure you check light bulbs and electrical equipment before continuing with work, as there is a possibility that the problem is not with the switch
Step 2. Make sure that no exposed wire parts touch the metal switch box
This will cause a short circuit and prevent electric current from flowing into your lamp. Cover all exposed wires with electrical insulation, or cut the exposed parts and pull the wires in so that there are no excess wires in the switch box.
Step 3. Check the connection of the cables
Many problems come from poor or loose joints. Unscrew some of the screws from the source and neutral wires. Make sure the cables are securely attached to the screws before tightening the screws again.
- Use pliers with slender clamps to secure the ends of the wires around the screws.
- Make sure that the exposed end of the wire is sufficient for connection to the terminal. Use a pair of cable strippers to strip at least half an inch of the cable.
- If the ends of the wires are falling apart or chipped, cut them off, strip the wire back 2.5 cm long, and use the ends that were just peeled off.
Step 4. You have some live power source wires
This is commonly found in older switch boxes, i.e. when two single switches are linked together instead of using a double switch. The electrified wire (red or black) goes out of the wall and into one of the switches, then out of the switch and into the other switch. In some cases, it may re-enter the wall after exiting the second switch. But don't be confused, just connect the source cable to the new connection as you found in the old cable connection. This is the reason why there are two terminal screws on the source side of the switch.
Some electricians will cut the cable cover in the middle, then twist the wires around the terminals, and allow the remaining wires to re-enter the wall. It's a good idea to do the same when you find this on an old switch
Step 5. Make sure you attach the source cable to the correct side of the switch
If after checking the connection of the switch it is not working, you should make sure that the source cable is connected on the correct side of the switch. If your switch doesn't have a marking, it's usually the one with the metal label, or "metal plate" on the correct side. The screws are generally black.
- If there are two black terminals on the same side, connecting the source cable to one of them is not a problem.
- If the problem persists, swap the connections and check your switch's user manual.
Step 6. You don't have a ground wire
Many older homes don't have a grounding wire, but this isn't a problem. Your switch box is already grounded to your home, which means you don't need a ground wire anymore.
Tips
- Be sure to read the instructions on the switch and on the connection you are going to connect as you will need to know the amperage in amperes required; both must match the equipment to be powered by the switch and its connecting cable.
- Mark the wires you already know with insulation so you don't get confused for the next one.
- Put a piece of electrical insulation along the circuit breaker when you turn it off to warn others not to turn it back on.
Warning
- Tell people around your house that you are working with electrical equipment.
- If you are not comfortable working with power tools, call an electrician.
- If you find that your cable is made of aluminum, stop your work and contact a professional cable specialist.
- Anticipate emergencies and have your first aid and emergency kit ready near you, even if you believe you can work without problems.
