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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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