Two Way Switching Explained | How to Wire a 2 Way Light Switch

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▶ Check out the full blog post over at
realpars.com/two-way-switching/
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⌚Timestamps:
00:00 - Intro
00:21 - SPDT switches
01:15 - Two-way switching Circuit
01:38 - Wiring in the EU and North America
02:10 - NMD90 14/2 & NMD90 14/3
02:56 - Power cable wiring
04:11 - Earth ground wiring
04:32 - SPDT switch wiring
05:27 - Flow of Electricity
In this video, we’re going to show you how a circuit is wired allowing you to turn a light on or off from two different locations. We are going to refer to this light control circuit as a 2-way switching circuit.
If we are going to turn a light on and off from 2 different locations, we need 2 Single Pole Double Throw or SPDT switches.
An SPDT is called a 2-way switch in the European Union, and a 3-way switch in North America.
An SPDT switch has 3 terminals. It will have one terminal in and 2 terminals out.
Each terminal on an SPDT switch has a name. The input terminal is called Common. The output terminals are called Normally-Open and Normally-Closed.
Operating the toggle or lever will cause the Common terminal to connect to the Normally-open or Normally-closed terminal depending on its position.
We have a switch at the bottom of the stairs and another switch at the top of the stairs. And, of course, our ceiling light over the middle of the stairs.
Circuit wiring is very similar in the European Union and North America but there are some differences. Electrical power supply wire insulation colors are different.
In this video, we will be referring to North American cables and wire colors.
In North America, the voltage is 115 Volts AC.
In North America, the 2 electrical power supply wires are called Line and Neutral and originate from a Circuit Breaker in an Electrical Panel. The Line wire has black insulation and the Neutral wire has white insulation.
The cable that leaves the Electrical Panel will contain these 2 wires plus a third wire which is connected to Earth Ground. The Earth Ground wire has no insulation.
The cable is referred to as NMD90 14/2 because of the size of the conductors and the number of wires inside. NMD90 14/2 has 2 wires sized at 14 AWG.
The cable could enter at the light or either of the switches.
We will explore a wiring circuit where:
- The power enters at the Down Switch
- There is a cable that runs between the 2 switches
- And another cable that runs from the Up Switch to the light.
Before we go any further, this is a good time to remind everyone that working with electricity is very dangerous! Leave the electrical work to qualified technicians!
For all electrical circuits, the bare Earth Ground wires are connected and bonded to each electrical box.
We’ve introduced a new cable. This new cable is called NMD90 14/3 and has a third red wire.
The electrical power black wire connects to the Down Switch common terminal.
The power white wire does not connect to the switch at all but is connected to the white wire of the 14/3 cable. The wire connection is completed inside the switch electrical box.
There is another wire connector securing the 14/3 white wire to the 14/2 white wire of the light cable. Again, this wire connection is completed inside the Up Switch electrical box.
The 14/3 cable connects the 2 switches. The red wire connects the switches normally open terminals, and the black wire connects the normally closed terminals.
And finally, the black wire of the light electrical box connects to the Up Switch common terminal.
Let’s see if it works!
With the switches in the positions shown, the electricity will flow from the line wire through the light and back to the neutral wire.
What happens if we change the Down Switch position? The electrical circuit is broken and the light goes off!
Let’s see what happens if we change the Up Switch position.
If all goes well, the light will come on. With the switches in the new positions, the electricity will flow from the line wire through the light and back to the neutral wire.
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[@volkerloebe4563]

Thank you for this video. Only on point. In EU we are using 230VAC (220VAC was the standard before)

[@anoopgeorge9483]

These type such simple videos we never expecting from realpars

[@roseelectronics4582]

True. It surprised me too.

[@archive9994]

This is not simple this is engineering

[@anoopgeorge9483]

I know its engineering but we want advanced technology videos not these type basic wiring

[@archive9994]

@@anoopgeorge9483 you should skip this video

[@solanocorneliofarinafreyre7437]

Real pars no es solo para científico,es también para principiantes.

[@borinvlogs]

SPDT single pole double throw

[@dancurts9300]

fantastic simple diagram and great explanation. saved me about $200. Thanks so much

[@realpars]

Glad it helped! You're very welcome!

[@willpaes]

Great video. Congratulations.

[@realpars]

Thank you!

[@speway]

I was at Homedepot and Lowes looking for a two way switch and couldn't find one for the life of me. 00:37 seconds into this vid and I know why. Oh my goodness.

[@andreyace8768]

Thank you!

[@realpars]

You're very welcome, Andrey!

[@elektriskietikli8497]

Good video for our design engineers. Thank you.

[@realpars]

Thank you!

[@NipkowDisk]

I read a number of years ago that the reason they are called "3-way" switches in North America, is because "way" is an older definition for "terminal". Looking also at a 4-way switch, that would make sense.

[@davidcooper4385]

4 way switch is a double pole double throw switch 15 or 20 amp spec,tech spec commercial grade switchs ,blue is 15 amp,20 amp red....

[@sukruuluslu3422]

Thank you for your sharing. Please make videos about Robot Programming and communications. Like ABB Robots

[@realpars]

Hey! Thanks for your comment and your suggestion. I will pass this on to our course developers! Thanks for sharing and happy learning!

[@ricardobarabad7131]

Pls make video 4-way switch. Thanks

[@vishyandypurandat6208]

Very well explained.

[@realpars]

Thank you!

[@amyjojinkerson]

we used B.X cable with antishorts

[@ricardogarcia3900]

Good video. Back to the basics. Congrats.

[@realpars]

Thanks a lot, Ricardo!

[@bryanz5904]

Thanks a lot for teaching! May I ask, how to define the neutral wire？ I mean IEC up to 16mm2 the neutral wire could be half size of the Line Cable. Where can I find the regulations in IEEE codes or other US codes? Please help.

[@realpars]

Hi @Bryan Z. Thanks for your question. As you probably already know, neutral size is dedicated by country and sometimes regional electric codes. The National Electrical Code (NEC), or NFPA 70 Section 220-22 deals with Neutral Size.

[@bryanz5904]

@@realpars Thank you so much for your help, thanks:)

[@mavamQ]

I came here from the website, the only quibble I have is with 14/3 wire. If there is a 20 amp breaker, the wire should be a 12/3 wire, even though a light circuit will not have high amperage, unless there is a short and then the 20 amp breaker protects the 12/3 wire, but not as well for 14/3. At least that is my DIYer understanding.

[@realpars]

Hi there. Thanks for reaching out. Yes, you are correct. 12awg wire should be used in a 20 amp circuit. Thanks for pointing that out. Next time, we'll use a 15-amp circuit. 😊

[@JinxedJax]

Did you know some surgens prefer obsidian over a metal scalpel? 😂

[@archive9994]

Please makes more videos in Electrical motors transformer generator switchgear troubleshooting Thank you

[@realpars]

Thanks for your feedback, Nikola! Happy learning.

[@sazzadhossan4206]

I am a Fresher BSC engineer in EEE.Can Anyone suggest some skills for remote job related to EEE field?

[@emailfilters]

[edit] 4:35 - The image is of AC90 (armored cable) not non-metallic cable! 0:08 - Unless your target audience is in a foreign country, you might want to just stick with the terminology that will be encountered in the field: "Three-way switch circuits and three way switches" (and the four-way switches included when controlling the device from more than two locations)! An electrician in Texas, for instance, would look at you like an idiot with three heads if you called it a two way switch! It's a good way to get fired the first day on the job.

[@realpars]

Hiya! Yes, you are 100% correct. The image is armoured cable. We do have a very large international audience so when it comes to using certain terminology we might look like "an idiot with three heads" in one country, but an electrician with only one head in another. We appreciate your interaction and feedback! Thanks a bunch!

[@emailfilters]

@@realpars Sorry for the trollbridge (pay at the other end what it's worth), just want everyone to be clear!

[@ddee2501]

... or you could use a PLC.... 😉

[@archive9994]

No more wiring

[@davidcooper4385]

Residential lol,a plc NO most electricians don't know what a plc is lol....

[@MaNemUmar]

Yes and pay 350-500 dollars for a situation that can be solved in less than 50 dollars

[@ddee2501]

@@davidcooper4385 I am an electrician and i have wired countless two, three, four way switches. But a PLC would be more fun :-)

[@ddee2501]

@@MaNemUmar its called "upselling" lol

[@adfggffffffddffd]

Once again, America gotta do things the stupid fucking way by calling a switch, that switches between TWO fucking contacts, (that's TWO functions) a 3 way switch.... FML

[@TefenCa]

Well, other North American countries joined them... The real question is: Why didn't people just use SPDT to begin with so that nobody screwed it up and it could have been universal? uhg...