If you’re an electrical apprentice, electrician or home DIY’er, knowing the difference between a single pole switch vs 3 way switch is important. Switches come in a variety of configurations designed for specific use cases.
In this article we will look at various switch types and explain the difference between a single pole vs 3 ways switch configuration as well as other common switch configurations.
What is a Single Pole Switch?
A single pole switch, in simple terms, is what you use everyday to turn a light on or off in a room. It is simple in construction and wiring a single pole switch is straight forward. Sometimes referred to as a toggle switch, a single pole switch has two terminals and one contact.
By turning the switch on or off, you effectively open or close the contact. When the contact is closed, electrical current will flow. When the contact is open, no electrical current will flow. If you connect the switch in series with a light then you have created a control circuit for you light.
The example wiring detail below shows a simple single pole switch circuit controlling a light. Notice the conductor (wire) color coding scheme that uses Non-metallic Sheathed Cabling (NMSC) also known as Romex.
This type of cabling comes with two conductors, one Black conductor and one White conductor, as well as a bare copper bonding conductor.
It is clear that two NMSC cables would be needed to complete this circuit if the Source indicates the feed originates from the circuit breaker distribution panel.
What is a Double Pole Switch?
A double pole switch, as you may have guessed, has four terminals and two sets of contacts that operate together. Sometimes referred to as Double Pole Single Throw (DPST) switches. This is because it has one operating handle (similar to your simple wall light switch), however, turning the switch on or off opens and closes two contacts.
The image below shows a double pole switch schematic representation. The dashed line between the to contacts means they are mechanically linked. If you open one you open up the other, and vice versa.
These types of switches are usually used to control two-phase type systems. For example, it is more efficient to operate motors at 240VAC than at the standard 120VAC. At 240VAC you have two line conductors (wires) that connect to your motor.
Therefore, to control a two-phase motor operating at 240VAC, you need to make or break both phases, otherwise, you will single-phase the motor. See the illustration below:
What is a 3 Way Switch?
Things start to get a little more complicated when we talk about a 3 way switch. Three way switches are commonly used in homes where you have an elevation change. For example, if you have a two-story home it is required for a light to be above the staircase.
In this scenario you will have a 3 way switch at the bottom of the stairs to turn the light on before you walk up. Then, at the top of the stairs, there will be another 3 way switch to turn the light off. This allows you to control the light from two different locations.
A 3 way switch has three terminals, they are, a common terminal and two traveler terminals:
Below, we provide a schematic of the simplest 3 way wiring configuration. Notice that when using a three way switch, you are required to use a three conductor NMS cable.
These cables typically come with a Black, Red and White conductor (also included is the bare copper bonding conductor, however, this isn’t usually counted).
Spend some time to analyze the schematic representation below. How many 3-conductor NMS cables will you need to wire up this lighting circuit? How many 2-conductor NMS cables will you need?
Did you figure it out? If you said, one 3-conductor cable and two 2-conductor cable you are right!
The first 2-conductor NMS cable is used to connect the Black wire to the common terminal of the 3 way switch from the circuit breaker (Source). The White wire is the neutral conductor. The adjacent pictorial representation of the actual box wiring shows this White wire is spliced (connected) to the White wire of the 3-conductor NMS cable.
The 3-conductor cable is used to go between the two 3 way switches. The Black and Red wire is used as the travelers (or signal wires), and the White wire is used to continue the neutral conductor to the light.
Finally, we use one more 2-conductor NMS cable to go from the common terminal of the second 3 way switch to the light. Again, the White wire is spliced in the box to connect the neutral conductor to the light.
We’ve omitted talking about the bonding conductor here. However, it is extremely important to bond all metal parts throughout the entire circuit using the bare copper conductor inside the NMS cable. It is always a good idea to contact a local professional when doing any wiring of any kind.
There are many different ways to wire a three way switch depending on where the Source feed originates. We encourage the reader to check out this video on different 3 way switch wiring configurations:
What is a 4 Way Switch?
If we didn’t confuse you enough on the 3 way switch wiring, let’s introduce another common switch type and that is the 4 way switch.
A 4 way switch has four terminals and still one operating mechanism like a single pole switch or a 3 way switch. However, when you switch a 4 way switch on or off, it effectively crisscrosses the travelers.
Head scratcher right? Let’s use an illustration to show you what we mean.
Depicted in image A, when the 4 way switch is off, the travelers are permitting flow in a straight fashion. However, in image B, when the 4 switch turns on, the travelers are crossed.
It is important to realize that a 4 way switch is never used on its own. It is only used in conjunction with two 3 way switches. Meaning, when you need to span a great distance (say in a gymnasium or theater and not just a staircase), it is sometimes useful to have switch control at intermediate places along the way.
To accomplish this intermediate control, you can insert one or more 4 way switches in between your two end-point 3 way switches. The other cool thing is, there is no limit on how many 4 way switches you can install. You can have one or one-hundred! So long as they are inserted between your 3 way switches you’re good to go!
The schematic representation below shows one 4 way switch installed in between two 3 way switches. As already mentioned, there really is no limit on how many 4 way switches we can install, it will still work as intended from a control perspective.
As you can see, with the introduction of a 4 way switch into our 3 way switch light circuit we will need another 3-conductor NMS cable.
We hope this article has provided you with the answer to a single pole vs 3 way switch. Our goal was to provide as much insight into this question as well as provide some additional knowledge with other common switches.
If you enjoyed this article, we recommend you check out some of our other articles on similar topics. You can check them out here.