How to control a light circuit from three locations

 

This is useful for example, you might use this to control the lights on certain stairwells leading to different floors, 

or from either side of the beds and one at the bedroom door, as in a hotel room.

Using two 3-way switches and one intermediary switch, the wiring schematic shows how to control a light from three separate locations.

Both switches have an identical appearance on the front, however, the three-way has three terminals on the rear. The switch can only be flicked up or down, but energy can flow through it in four different ways depending on how it's linked to the circuit. 

The intermediate switch can only be flipped up or down, although there are four terminals on the rear. Depending on how the circuit is constructed, electricity can flow through this in 14 different ways. I've included some sites below where you can get both of these switches for a reasonable price. 

The design of these intermediate switches is quite brilliant. The switch contains a mechanical component, which means that when it is flipped, it crosses its rails, changing the direction. These two tracks are kept fully separate and do not touch. We can therefore reroute the power and make or break the circuit by crossing its pathways to change the direction.

How to connect 1 light control by 3 three switches

At each end, we have three-way switches, with an intermediate switch in the middle. We attach our live conductor to the common of the three-way switch 1. Then we connect terminal 1 of three-way switch 1 to terminal 2 of the intermediate switch with a wire. Then we run a wire from the intermediate switch terminal 1 to the three-way switch 2 terminal 1. After that, we run a wire from three-way switch 2 common to the lamp's live side. We connect terminal 2 of three-way switch 1 to terminal 4 of the intermediate switch with a wire. Then we run a wire from the intermediate switch's terminal 3 to the three-way switch 2 terminal 2. Then we run a last wire from the neutral to the lamp's neutral side.

How does work? 

• Current begins to flow from the source through the common terminal on three-way switch 1 when three-way switch 1 is flicked. Then from the three-way switch 1 terminal 1 to the intermediate switch terminal 2. Then from the intermediate switch's terminal 1 to the three-way switch 2 terminal 1. Then to the light via a common terminal on three-way switch 2. Then through the neutral, back to the source.

Any of the three switches can be flicked to turn off the light.

Three-way switch 1 flicked

Intermediate switch flicked

 

Three-way switch flicked

• When three-way switch 2 is flicked, current begins to flow from the source through the common terminal on three-way switch 1. Then from terminal 2 of three-way switch 1 to terminal 4 of intermediate switch Then from terminal 3 of the intermediate switch to terminal 2 of the three-way switch 2. Then, via a common terminal on three-way switch 2, to the light. Then back to the source via the neutral.

Any of the three switches can be flicked to turn off the light.

Three-way switch 2 flicked

Three-way switch 1 flicked

Intermediate switch flicked

• When the intermediate switch is flicked, current begins to flow from the source through the common terminal on three-way switch 1. Then from terminal 2 of the three-way switch 1 to terminal 4 of the intermediate switch. Then from terminal 1 of the intermediate switch to terminal 1 of the three-way switch 2. Then, via a common terminal on three-way switch 2, to the light. Then back to the source via the neutral. An example of this is below

                                                         🠋 

Any of the three switches can be flicked to turn off the light.

Intermediate Switch Flicked

Three-Way Switch 2 Flicked

Three-Way Switch 1 Flicked

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