This article will help you understand the different methods on how to wire a single light switch. Read on to see which method applies to your application. Hopefully we can clarify it for you.
As per 2018 current electrical code. You are required to have power running though the device box when planning on how to wire a single light switch. Needed is a neutral or white wire present inside the switch box.
10 Methods On How To Wire A Single Light Switch
- Wiring a single pole switch
- How to wire a double pole switch
- 3 way switches
- Wire a 4 way switch
- Terminating several switches
- Does it matter which wire goes on the light switch
- How do I wire a single light switch with 3 wires
- What if the power wire runs to the light first
- What amperage does the switch need to be
- Why is there a ground wire on the light switch
Wiring A Single Light Switch Single Pole
Wiring a single pole switch is relatively easy. Inside of the wall box you will see two black wires coming out to the switch.
Those two black wires break the actual circuit going to the lake. You also see two white wires they get wire nuted.
If you follow the diagram below you can see quite clearly that the power feed comes from the power source. In this case it would be from the power panel.
This would be a 120 V power feed. The power feed then would terminate inside of the switch box. The load side of the switch would then terminate at the light box or in this case spotlights.
This is the most simple form when it comes to how about to wire a single pole switch.
You will notice as mentioned above the white or neutral wire carries right through to the light fixtures. This type of wiring is usually done with NMD 90 14/2 wire.
How To Wire Single Light Switch Double Pole Application
When wiring a double pole switch the process is slightly different. A double pole switch actually breaks both sides of the circuit.
This method is commonly used for shutting off 240 V loads. Since 240 V loads do not have a neutral wire it is considered by code to be safe to break both sides of the circuit.
An example of what this would be used for would be to turn off and on a hot water tank. It could also be used for turning on or off a safety switch for any 240 volt loads like a water pump.
On the back of the switch it will have an actual line side and a load side.
Wiring 3 Way Switches
The diagram below shows common uses and common wiring of a basic three-way switch. Three way switches are used for areas like hallways or top and bottom of staircases.
They help switch a light or several lights from two locations. You may often hear them referred to as a two way however the proper terminology is a three way switch.
In this case the power is coming from the panel through the first switch box to the second switch box and then to the light fixture.
Notice that The wire coming from the panel is a piece of 14/2 nmd. The wire between the two 3 ways is actually a piece of 14/3. This extra wire between the two 3 ways is for the travelers to work.
The commons or terminals on the three ways receive power from the panel.
The last common on the second three-way goes back up to turn the light off and on. The travelers go between the two 3 ways.
This creates a flip-flop action between the 23 ways which actually transfers power from one location to another to then turn off or on the light fixture.
You can find more on 3 way switches here.
How To Wire A 4 Way Switch
Wiring a 4 way switch is more complicated. A 4 way switch is installed between two 3 way switches. This is so you can switch the light from 3 different locations.
These installations are common in larger homes with big rooms that have a few entrances.
To simplify a 4 way it simply changes the direction of the power on the travelers between the two 3 ways.
It would be installed as a center point in the 14/3 wire running from 3 way to 3 way.
The red and black travelers of the 3 wire would be broken by the 4 way switch.
Wiring Several Switches
Since we talked about 4 ways, it is easy to understand that you can have as many as you like in a light circuit.
The 4 way goes between the two 3 ways. You can have as many 4 ways as you like between them. This allows the light to be switches from several positions.
There are also smart switches on the market today that simply wire into any power circuit to control lights.
That simplifies the wiring process however a bit more expensive up front.
You can find out more on this type of switching system here.
Does It Matter Which Wire Goes On The Light Switch?
Most common single pole light switches do not care which black hot wire goes on them. They will still break the circuit and do their job.
With that being said, dimers, timers or anything electronic does matter.
It’s important to get the line and load correct on an electronic device. it will simply not work unless you do.
Unfortunately the only way to really tell the line load of a switch is to test for power with a voltmeter.
How Do I Wire A Single Light Switch With 3 Wires
When you run into a switch with 3 wires it is usually because power was run through the switch to give constant power to an outlet.
We do this when we have power at the light and want to drop a plug below the wall switch box. The piece of 14/2 wire feed from the panel runs to the light box or octagon first.
Then we drop a piece of 14/3 down to the switch box. Another piece of 14/2 drops from the switch box to the plug.
The white wire actually goes right through the switch box down to the plug. The black wire also goes through however has a tail to power the bottom of the switch.
The red wire or third wire goes back up to the light to switch it on and off.
What If The Power Runs To The Light First?
The diagram below show the power coming into the light fixture first. It then drops to the switch to make or break the circuit.
As per new code we are now required to drop a neutral wire to the light switch.
You will notice that the example is actually a set of three way switches. The common coming back up from the switches returns to the light box to turn it off and on.
What Amperage Does The Switch Need To Be ?
Generally a light switch is 15 amp. Some switches have a 20 or 30 amp rating of them but most switches in residential are just 15 amp.
When you get into larger switching applications it usually consists of relays doing the switching.
This is usually done in larger commercial applications like stores, arenas etc.
One switch can control several relays to turn off and on several banks of lights. The relay itself can control multiple circuits at once.
Why Is There A Ground Wire On The Switch?
The ground wire is on the switch to ensure the switch has a good ground. many electrical boxes can contain plastic not making a good ground.
Even worse sometimes when the wall material is replaced like the drywall or plaster.
The electrical box sets too far back in the wall to make proper contact with the device. Having a ground right on the switch ensures a ground.
In a case like this we use what is called a plaster ring or a box extender.
The device screws onto the front of the electrical box which extends its length.
This allows for the plug or switch to make direct contact to metal supplying a good ground.
Careful though some switches can fool you like a 3 way. We have seen ground wires hooked on the common of a 3 way causing a short circuit.
Look for the green terminal screw. This indicates ground.
As a 2018 current electrical code requirement we have to extent the ground wire or bare copper wire from the end of the box long enough to attach to the switch.
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