A conventional light switch is the simplest switching device that, when a button is pressed, opens or closes a contact, thereby turning off or turning on the lighting device. Switches can be either one-key or two- or three-key, depending on the number of lamps or their lighting groups that are planned in the room.
However, when connecting a lamp, light bulb or chandelier, the question arises: which of the conductors of the standard single-phase break the circuits by connecting to the switch so that the lighting system works correctly, durable and safe for man?
As you know, the standard network of an apartment, private house, garage or other residential premises is connected to a 220/230 Volt network, in which one of the conductors is phase, and the other is zero. It is the phase wire that carries the energy for the lighting device, which is then converted into light emitted by the source. However, without creating a closed circuit through the luminaire, to which both phase and neutral conductors must be connected, the operation of the lighting device is impossible.
Switch connection options
Structurally, a standard switch, which is often used indoors, makes it possible to break only one of the two network conductors.
There are two options for connecting a conventional switch:
- break of the phase wire and its connection to the switch;
- connection of the neutral conductor to the switch terminals;
Both methods will stop the operation of the lighting device, however, the first option, according to the rules for electrical installations (PUE), and specifically paragraph 6.6.28, is more correct and safer.
Connecting the phase conductor to the circuit breaker is based on one but very important advantage.
The possibility of replacing the lamp of the luminaire without completely disconnecting the line, since according to such a scheme with an open contact switch, potential dangerous to humans on the luminaire body, in the holder or its other element cannot be in principle. Of course, provided that the switch is in good condition. It will also be correct to organize the lighting circuit using protective grounding, especially in if the luminaire bodies are made of conductive material (metal, etc.) and this is indicated in paragraph 6.1.37 current rules of the PUE.
Consider a circuit where the switch is connected to a neutral conductor.
As you can see from the diagram, the phase, the dangerous potential will always be present on the luminaire, which causes danger and inconvenience during its maintenance. Also, if an incandescent lamp with a low resistance is installed in the lighting equipment, then voltage will also be present on the switch (on the outgoing contact). Thus, both a switch and a lamp will be under a potential hazardous to humans, which is very inconvenient and very dangerous.
Therefore, according to the current rules, experienced electricians, professionals in their field, will always connect the phase wire to the switch, and not the zero one. In any case, I would like to remind you that when repairing, operating, connecting, replacing lamps and other work on current carrying parts, it is necessary to turn off the circuit breaker or the voltage supply switch, and also take all measures so that it is not mistakenly included.