Replacing a Light Switch and Changing the Wiring
Dina in Maryland asks; How do I connect the wires when replacing my light switches? How to Replace a Light Switch and Make the Wiring Connections, Identifying the Wiring, Connecting the Wiring for Your New Switch.
Wiring Light Switches
Electrical Question: How do I connect the wires when replacing my light switches?
I need to replace a single light switch, but when I pulled the old switch out of the wall here is what I discovered:
The switch has three wires attached to it, in addition to the grounding wire. Two of these wires are pushed into the back of the switch, the 3rd one is around one of the screws on the side. The new switch that I bought only has two screws, not counting the grounding screw. How do I connect this? I’m not sure if all three of the wires going into the old switch are “hot” or if only two are hot, which ones they are. What would that third wire be from? I also noticed on the old switch that it says “CU and CU Clad Wire only.” This means that I have copper wires, not aluminum, correct?
Thanks in advance for any help you can provide.
This home electrical wiring question came from: Dina, a Homeowner from Baltimore, Maryland.
Thanks for your electric wiring question Dina.
How to Replace a Light Switch and Make the Wiring Connections
Application: Wiring for a Light Switch.
Skill Level: Beginner to Intermediate – Best performed by a Licensed Electrical Contractor.
Tools Required: Basic Electricians Pouch Hand Tools and Voltage Tester.
Estimated Time: Depends on personal level experience and ability to work with tools.
Precaution: Identify the light circuit, turn it OFF and Tag it with a Note before working with the wiring.
Notice: Installing additional electrical wiring should be done according to local and national electrical codes with a permit and be inspected.
Electrical Wiring for Light Switches
Identifying the Electrical Wires When Replacing a Light Switch
- The top portion of the switch where the one black wire is closest to the terminal for the bare ground wire should be the wire that leads to your light fixture.
- The two wires attached at the bottom portion of the switch should be a power source coming in and a power feed going out to other devices.
When Connecting the Wiring for Your New Switch, this is what I Recommend:
- Reconnect everything as it is, except the bottom two wires should be pig-tailed.
- This means that the two wires should be spliced together along with a third wire (the pigtail) which will be connected to the switch.
- A yellow or red wire nut can be used for this splice.
- If the length of the two wires is long enough, you can trim them shorter and use one of the cut wires for the pigtail.
- Attached the pigtail to the side of the bottom screw terminal of the switch.
Electrical Wiring Abbreviations and Terms about Light Switch Wiring
- AL is the abbreviation for Aluminum, and CU is the abbreviation for Copper, which are used to describe the compatibility or designation for electrical wiring and the associated components.
More about Wiring Light Switches
- Wiring a Light Switch – Diagram 1
- Fully explained pictures and wiring diagrams about wiring light switches describing the most common switches starting with photo diagram 1.
- Electrical Wire for the Home
- Complete listing of electrical wire types and parts used for home projects with electrical code information serves as selection guidelines.
Consult your Local Building Department about Permits and Inspections for all Electric Wiring Projects.
The Safest Way to Test Electrical Devices and Identify Electric Wires!The Non-Contact Electrical Tester
This is a testing tool that I have had in my personal electrical tool pouch for years, and is the first test tool I grab to help identify electrical wiring. It is a Non-contact tester that I use to easily Detect Voltage in Cables, Cords, Circuit Breakers, Lighting Fixtures, Switches, Outlets and Wires. Simply insert the end of the tester into an outlet, lamp socket, or hold the end of the tester against the wire you wish to test. Very handy and easy to use.
The Quickest Way to Check for Faulty Electrical Wiring!The Plug-In Outlet Tester
This is the first tool I grab to troubleshoot a problem with outlet circuit wiring. This popular tester is also used by most inspectors to test for power and check the polarity of circuit wiring.
It detects probable improper wiring conditions in standard 110-125 VAC outlets Provides 6 probable wiring conditions that are quick and easy to read for ultimate efficiency Lights indicate if wiring is correct and indicator light chart is included Tests standard 3-wire outlets UL Listed Light indicates if wiring is incorrect Very handy and easy to use.
Strip Off Wire Insulation without Nicking and Damaging the Electric Wire!The Wire Stripper and Wire Cutter
My absolute favorite wire stripping tool that I have had in my personal electrical tool pouch for years, and this is the tool I use to safely strip electrical wires.
This handy tool has multiple uses:
The wire gauges are shown on the side of the tool so you know which slot to use for stripping insulation.
The end of the tool can be used to grip and bend wire which is handy for attaching wire onto the screw terminals of switches and outlets..
The wire stripper will work on both solid and stranded wire. This tool is Very Handy and Easy to Use.
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