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Switch goes and come back

The amateur electrician is sometimes a little lost face to the scheme of connection of a back and forth. To be well understood, this very practical assembly requires to proceed methodically to allow the flip-flop of operation between the two control points.

A diagram that may seem relatively complex

The back-and-forth circuit is one of the most conventional electrical connection fixtures. This is not the most complicated, but it often gives "the twitch" (it is the case to say it) to the amateur electrician. The slightest confusion between connections causes the system to malfunction. It is used to turn on and off a light point from two points distant from each other. This is the ideal installation to install at both ends of a corridor or on two levels of the stairwell of a house. The disadvantage of this type of installation is that it does not control the lighting from more than two separate points. That is why it is often preferred today the remote switch, both more convenient and easier to install. The latter, however, relay which penalizes the cost of the installation. It should be noted that we can install a double back and forth.
There is a simple way to fully understand the mounting a back and forthis to carry out beforehand a electrical diagram, as is done for any electrical installation. In this way, editing will be greatly simplified.

To avoid making mistakes

To achieve a consistent and secure connection, it is important to follow some basic tips:
respect the color code the wiring diagram,
use switches because conventional switches are not suitable,
watch out for the confusion of the threads! The terminals of the shuttle must be connected to each other,
think about the earth to protect the lighting,
do not install multiple switches one behind the other,
install a remote control if you need to turn on the lights for more than two points.
At the color level, the theoretical diagram below illustrates what can be done in reality:
red phase (up to the switch input), then Brown (at the output of the switch and up to the lighting),
orange shuttles,
neutral blue after the lighting.
It is particularly important here to respect the color code. The son of land Green yellow is not shown here since it is not an active conductor, but it must be connected to the luminaire.

Diagram of back and forth

electrical diagram of a switch back and forth

Basic material to install a back and forth

The installation of a back and forth is done with rigid electrical wires normalized 1.5 mm section, so apparently under chopsticks, or flush-mounted, possibly by multiconductor electric cables under a chute in a workshop. This is a "lighting" circuit which, as such, is protected at the electrical panel by a differential switch or a divisional circuit breaker of 10 A. If the installation still includes fuses, it will be an opportunity replace them to modernize the installation. The connections are made at the level of the devices by screw terminals and, at the level of the boxes, with automatic terminals which advantageously replace the dominoes. It will be observed that there are switches with indicator light, easily recognizable in the dark. There are also dual function devices: switch on one of the rocker buttons, simple switch on the other.

Specific switches

The switches of a back-and-forth installation are specific. We often speak of "switchesThey include 3 terminals, as opposed to 2 for a single switch.The "main" terminal receives the phase or return wire to the point (s) of use (usually lights, but potentially also outlets). The other 2 terminals connect the switches to each other and are called "shuttles." When one of the switches is operated, it sets a switch that reverses the state of the circuit by opening or closing it. The switch is reversed on the other switch, in a corridor, for example, it switches on the lighting from one side of the installation, then off from the other. lighting from each of the two switches, so both ends of the corridor.

Note that a back and forth uses two switches (dual output switches), which are adaptations of the switch to this type of mounting.

(photos / visuals: © Legrand, except special mention)

On the same topic

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