LAMPS CONTROLLED FROM THREE LOCATIONS: THE INTERMEDIATE SWITCH (PRACTICE)

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In this practical lesson, we will see how to control a group of lamps from three different locations. To this end, we will learn how to install a new electrical component: the intermediate switch.

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We have seen in the theoretical lesson, that in the case of a lamp to be controlled from more than two locations, we must resort to the use of intermediate or crossover switches.

With reference to the case of three control points, we have considered the following wiring diagram in the theoretical lesson.

The installation of this circuit in our test room, can be carried out according with this diagram.

We observe that the hot wire, coming from the junction box,

reaches the common contact of the first single-pole double-throw switch.

The two traveler terminals of this switch are then connected to the intermediate switch.

The other two terminals of the intermediate switch are then connected to the two traveler terminals of the second single-pole double-throw switch.

The common terminal of this switch is then connected to one contact of the light bulb.

We observe that for the installation of this system, it is necessary to use four electrical conduits where the wires are housed.

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We have also stated in the theoretical lesson, that this is only one of the possible configurations.

As an example, let’s consider a second implementation of the system.

In this second implementation, we have changed the arrangement of the four electrical conduits. The implemented electrical circuit, on the other hand, always remains the same. In fact, we observe that the hot wire reaches the first single-pole double-throw switch. The two traveler terminals of this switch are then connected to the intermediate switch. Then we have that the other two terminals of the intermediate switch are connected to the two traveler terminals of the second single-pole double-throw switch. The common terminal of this switch is then connected to the bulb, and finally we have the other terminal of the bulb connected to the neutral wire.

In the current configuration of the switches, there is electric continuity between the hot wire and the light bulb, and consequently the bulb is on.

If, for example, we operate the intermediate switch,

the hot wire continuity is interrupted and the light bulb will be turned off.

Well, in this lesson we want to implement the circuit just analyzed.

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Thanks to the installation carried out in the previous practical lesson, we can see that the common terminal of the two single-pole double-throw switches are already connected to the lamp and to the hot wire.

In this photo, you can see a detail of the circuit which highlights the path of the wire that from the common contact of the single-pole double-throw switch, placed at the bottom position of the work table, reaches the bulb passing through the switch box on the right.

In this other photo we illustrate a detail of the intermediate switch and the four wires that must be connected to it.

We must in fact remember that the intermediate switch is equipped with four contacts to which the four wires already prepared for this purpose must be connected.

Before making the connections, it is clear that the wires must be inserted into the appropriate pipes.

The wire that goes from the lower left single-pole double-throw switch to the bulb must also run through the same tubes.

The connections of the single-pole double-throw switch at the bottom left position of the work table are highlighted in this other photo, where we can observe the two wires connected to the traveler terminals of the single-pole double-throw switch

We can see that they reach the electric box of the intermediate switch. 

The wire connected to the common terminal of the single-pole double-throw switch, instead, passes through the electric box of the intermediate switch in order to reach the lamp.

At this point, we can proceed with the connection of the intermediate switch.

It must first be inserted in the appropriate plastic support,

and then it must be connected to the wires that we have already prepared for this final connections.

Do not forget to tighten the screws to prevent the wires from slipping off when fixing the plastic support to the electrical box.

We observe that both the electric boxes and the flexible tubes have been fixed with adhesive tape.

At this point, everything is ready for the final check.

By flipping any of the three switches several times,  the light bulb will switch on and off alternately.

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Well, we have come to the end of this lesson. We have analyzed how to install a circuit that can control a group of lamps from three different locations by using the intermediate switch.

We suggest you immediately consolidate the concepts you have just learned by carefully reviewing this lesson and above all by going through all videos of our course, by accessing our playlists.

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Thanks for your attention and … see you next time!

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