Single pole switches are used when only one switch is needed to control one or more lights. They are the only switch labeled "ON" and "OFF" and the only switch with two terminal screws (with a third green ground screw). They are identified on blueprints as S1. The methods that follow are explained with 1) Line diagrams 2) Wiring schematics and 3) Photos . Line diagrams help electricians figure out how to make wiring connections by simplifying the circuit. Line diagrams are drawn with the hot on the left and the neutral on the right. Wiring schematics are more like a drawing of the real thing, like a road map. To keep the illustrations simple, the grounds are not shown. Green or bare wire grounds are connected together and to any metal parts in the circuit that are not supposed to be electrified, parts like a metal box (instead of theblue plastic box used here) and the metal canopy of a light fixture (instead of the white plastic light used here) and the metal yoke of the switch that has the green ground screw.
S1 Method #1-1 Basic Single Pole RatingExcellent A+ ☺
This is the most simple and common method of wiring a single pole switch. LevelBeginner DescriptionPower (a hot and a neutral) is fed to the switch with a switch leg run from the switch to the light: A 2 wire feed is pulled from the nearest source of power like a receptacle or the panel to the switch. 2 wire meaning; either 14/2 with ground (wg) for 15 amp circuits or 12/2wg for 20 amp circuits. A 2 wire switch leg is pulled from the switch to the nearest light.
A photo, diagram and schematic of a basic single pole switch circuit with one light.
Basic single pole switch circuit with one light. The cord plug at L1 (hot) and N (neutral) represents power feeding this
Compare the wiring schematic with the photo. To make switch wiring easier, try to visualize how the electrical current is moving through the circuit. For example, look at the wiring schematic and say to yourself, (the current is moving) ✘ "From the hot, through the switch, to the light and back on the neutral" *
"From the hot "
Electrical current begins at L1. This current is coming from the electrical panel or a nearby receptacle and arrives at L1 where it enters your light circuit. From L1, the current flows through the black wire to terminal #1 on the single pole switch.
"through the switch"
The switch is shown in the open or off position. Inside the switch, after the switch blade is closed, the current flows through the (purple) switch blade from terminal screw #1 to terminal screw #2.
"to the light"
It then leaves #2 and follows the next black wire called the "switch leg" to terminal screw #3 on the light fixture. The switch leg wire is only hot when the switch is on (closed). From terminal #3 current flows to a small point on the base of the light bulb where it then enters the bulb, flows through a highly resistant filament wire and then exits the bulb through the base shell which is connected to terminal screw #4 on the light fixture.
"and back on the neutral"
From terminal #4 current returns through the white neutral wire to the red wire nut connection and back to the neutral.
The part that is not shown is how current continues from the neutral to the panel to a transformer coil, through the coil in the transformer from N to L1 where it starts all over again, as explained in the "Introduction to Switch Wiring"
S1 Method #1-2 Basic Single Pole with 2 Switch Legs RatingExcellent A+☺ An easy and common single pole wiring method.
LevelBeginner Description Power is fed to the switch and 2 separate switch legs are pulled from the switch to 2 separate lights: A 2 wire (14/2wg or 12/2wg) feed is pulled from the nearest source of power to the switch. The first switch leg is run from the switch to the closest light at the left. A 2nd switch leg is run from the switch to the closest light to the right.
Remember our saying; ✘ From the hot through the switch, to the light and back on the neutral.
The only thing different here is that "light" and "neutral" are plural; ✘ From the hot (L1), through the switch (1,2), to the lights (3,4 and 3,6) and back on neutrals (5,8,N and 7,8,N).
A line diagram and wiring schematic of a basic single pole switch circuit with 2 lights.
Question; Does the 2nd light have to connect directly to the switch?
Answer; No. The 2nd light can be connected to any point on the switch leg (the switch leg is from 3 to 4 and 5 to 8) The next best connection point would be to connect the 2nd light to the first light (A black wire from 4 to 6 and a white wire from 5 to 7) Splicing into any other point along the switch leg is permitted as long as your connections are contained in an accessible junction box and the lengths of wire inside the box is 6 inches long. Additional lights can be added as shown below; A line diagram and wiring schematic of a basic single pole switch circuit with 3 lights.
Why run 2 switch legs to the switch? Answer; If the switch is located between 2 distant lights you will save wire.
Look at the house photo. A switch located by the door at #2 will control 2 lights; one light at #1 and another light at #3. Each light is 50 feet away from the switch. Installing one switch leg (14/2 with ground Non Metallic Sheathed Cable) from the switch at #2 to the first light at #1 (50 feet away) and interconnect the first light to the second light at #3 (100 feet away) would use 150 feet of wire. If you install 2 switch legs, one from the switch at #2 to the light at #1 (50 feet away) and a second switch leg from the switch at #2 to the light at #3 (50 feet away) you would use 100 feet of wire saving you 50 feet of wire. If you paid 20 cents a foot for the wire, you would save $10 (20 cents x 50 feet= 1000 cents or $10)
This savings only applies if the switch is between the lights. If the switch was located at #1 you would waste 50 feet of wire installing 2 switch legs; #1 to #2 (50 feet) and #1 to #3 (100 feet) (50 + 100 = 150 feet of wire)
In these first 2 methods we fed power to the switch box. In the next method, on page 2, power is fed to the light box; Page 1 / page 2 / page 3 / Key
Footnote; * In AC (alternating current) circuits, the flow of electricity "alternates" back and forth from the Line (the hot) to the Load (the light) and then reversing direction from the Load to the Line. When electricians talk about AC current moving through a circuit they speak as though the current is DC (direct current) flowing in one direction from Line to Load. The descriptions in these articles are also written as though the current is DC even though it is really AC current. Think of it as electrical current that is frozen in a split second moment in time moving from Line to Load. In the next split second the current will reverse direction and flow backwards from Load to Line, from the light to L1.