Two-key switch connection scheme for two bulbs

In some cases, instead of two or three conventional switches, it is advisable to install one group (two- or three-key). We suggest considering in which situations it is justifiable to use such devices and their design features. At the end of the article will be described in detail how to connect.

Purpose and scope

This type of device allows you to switch two or three (if a three-key design is used) groups of devices (light sources, exhaust hoods, etc.) or turn on / off individual groups.

Using the two-key design, it is easy to organize the control of the intensity of the lighting of the room. For example, if you use a light source with three bulbs, you can connect it so that two groups form. Then you can turn on one, two or all the lights at once. How to implement this option will be described below.

The second, no less common option is to control the lighting of a separate bathroom.

Of course, you can use two single structures for these purposes, but installing a double gives the following advantages:

• when installing structures of a hidden type, you will only need to make one seat;
• the cost of the one-key and two-key switches is approximately the same, but the first two are needed;
• two devices look less aesthetically pleasing than one, and take up more space, which can be critical in some situations.

Design features

Two-key devices for switching on / off the load are structurally almost identical to single-key devices, the main difference is the switching mechanism. Below, in figure 2, the main structural elements are shown.

Designations in the photo:

• A - keys;
• B - external panel-case;
• C is the inner panel;
• D - switching mechanism;
• 1 - input;
• 2 and 3 - contacts for control wires going to the chandelier.

Now we will consider how the circuit of the contact group of the switching mechanism is arranged; it is shown in Figure 3.

As can be seen from the presented diagram, the switching mechanism has three contacts, “1” - a common input, “2” and “3” - two control outputs.

Now that we have figured out the design of the two-gang switches, we can proceed to the circuit of their connection.

How to connect two-key switches

Consider the connection on the example of a two-section lighting device (the diagram is shown in Figure 4). Note that this is the standard option that is used to turn on / off any devices.

As can be seen from the figure, zero is supplied directly to the light sources, in contrast to the phase that is switched. When the contact “kl1” is activated, “L1” is turned on, respectively, “kl2” is responsible for the operation of “L2” and “L3”. As a result, we can set three options for the intensity of illumination in the room (one, two or all lamps are on).

Please note that the input "1" is supplied: phase, and the output two control lines ("2" to "L1" and "3" to the group "L2" and "L3"). The supply can be made with a three-wire cable, if it is not, then 3 wires are laid.

The option shown in Figure 4 is more general. Therefore, I will also give a simpler connection diagram specifically for 2 bulbs (lamps):

Why do I need to switch the phase?

The above circuit will function even if the polarity is reversed, but despite this, the phase conductor must be connected to the contact group (input “1”). This condition, set forth in the Electrical Installation Rules, is directly related to safety. If you switch zero, then the voltage will always remain on the contacts, which can lead to serious consequences during maintenance or repair.

Step-by-step instructions for installing the two-key switch on the hood and lighting in the bathroom

Suppose we need to install a two-key switch for hood and lighting in the bathroom. We assume that all the wires are already laid and let down, and the hood and the lamp are installed. Our task is to make the switching in the box and connect the equipment to the switch.

We will describe how to perform this work with the minimum amount of tool; everything that we will need is shown in Figure 5.

Tool list:

1. Phillips and slotted screwdrivers.
2. A special knife to remove insulation (you can take a regular one);
3. Four double WAGO terminals. They will be needed to make the connections. Of course, this can be done in other ways (soldering, welding, twisting), but we settled on This option, since it is the simplest, does not require a special tool and skills to work with him. Detailed information on WAGO terminals can be found on our website.
4. Level.
5. Probe (needed if wiring is made with monochrome wires).

The algorithm of actions will be as follows:

1. We de-energize the wiring in the switchboard - this is a prerequisite for the work.
2. We carry out the switching in the box, connect the zero to the common wire from the lamp and the hood, put the phase on the switch, connect the outputs from it to the control wires from the devices. In order not to be mistaken with the purpose of the wires, Figure 6 shows the standard color layout.

If the wires are longer, cut off the excess. Using a knife, remove insulation from them (about 10-15 mm from the edge) and connect them in the WAGO terminals,

1. We connect to the terminals of the switch, for this we cut off the excess and strip the insulation. Now it is necessary to bring the phase to the common input of the switching mechanism, if three single-color wires are removed to the connection point, you will need to find it. To do this, apply voltage to the wiring and the probe alternately touch the wires. When the search is found, a neon light will come on in the device. After that, turn off the voltage and continue to work.

We connect the control wires from the hood and the lamp to the outputs of the switching mechanism, the order of connection does not matter.

1. We install in a glass (if the device is a hidden type) or in a prepared place (external execution), after which we set the external panel in level.
2. We connect the hood and the lamp. They are usually equipped with a terminal block; if not, WAGO double terminals can be used.
3. At the final stage, we check the operation of the assembled circuit. If you adhere to this algorithm of actions, then there will be no problems.

Note that the three-key switch is connected in a similar way, only 4 wires are required to connect it.