Electric lighting is widely used in modern residential and public buildings. To create the necessary comfort in rooms and save energy during daylight hours, the lighting is turned off, for which, in most cases, key switches are used. Rotary retro-switches functionally similar to them are rare, and dimmeters have not yet found widespread use.
Although the breaker is usually square in shape, this is dictated by a 45x45mm mounting socket (European standards 50 × 50 and 55 × 55 are possible, but not so popular), vertical orientation is considered natural keys. But there is no consensus about the position in which the key should be when the light is on. Moreover, the PUE and other regulatory documents do not contain any instructions in this regard.
"Natural" position of the switch
Nevertheless, the issue with the orientation of the switch can be resolved with the involvement of common sense, established traditions and references, albeit not direct ones, to regulations from related areas.
It seems reasonable to assume that the rocker switch is one of the options for the knife switch. For these power circuit components PUE, in clause 4.1.9 regulates that the control element should not spontaneously move into the working position under the influence of gravity. In fact, this means that the switch handle is moved to the working position by a movement from the bottom up.
The control scheme familiar to the circuit breakers is directly transferred to the circuit breakers, the toggle switch of which in the working position is located on top, Figure 1.
The upper position of the control element is also adopted on other control devices. For example, on the still common Soviet-made AB series machines, the power button is also located on top.
Further, for reasons of uniformity, it immediately follows that in lighting systems, the included light must correspond to the recessed position of the upper edge of the key, as shown in Figure 2.
In some cases, the orientation of the keys is provided by the switch design. For example, the use of the built-in indicators shown in Figure 3 clearly indicates the installation position.
Exceptions to the rule
Exceptions to the rules listed above are quite possible, although they are quite few.
At first, sometimes the switch has to be literally turned upside down simply because there is not enough wire. Those. this solution is the only way to avoid the time-consuming pulling of a new wire.
Secondly, sometimes the traditional switch position is changed for convenience reasons. For example, horizontal orientation is used near a chair in situations where it is convenient to turn on the arm by moving the arm in a linear direction "away from you".