According to the “Electrical Installation Rules” (PUE), the bathroom is divided into zones 0, 1, 2, 3. Zone 0 is located inside the bath bowl or shower tray. Zone 1 is the space above zone 0. Zone 2 is an area 60 cm wide adjacent to zone 1. Zone 3 is the volume bounded by the outer surface of zone 2 and a vertical surface located at a distance of 240 cm from it. Zones 1–3 reach a height of 225 cm from the floor.
In the bathrooms of apartments, it is allowed to install sockets with a voltage of 220 V only in zone 3. Moreover, all electrical installation products must have a moisture protection class of at least 4. In practice, this means that the socket housing is able to withstand individual splashes. Such sockets in the bathroom are supplied, in particular, with protective shutters.
Any switches and sockets must be located at a distance of up to 60 cm from the doorway of the shower cabin. All electrical installation products must be connected to the network through isolating transformers or be equipped with a residual current device (RCD) that responds to differential current, the strength of which does not exceed 30 mA. In practice, RCDs are usually used, since isolation transformers are less convenient. Transformers are usually used to connect electrical equipment of low power (50–100 W).
For devices with a power of 2–2.5 kW, an isolating transformer of solid dimensions, weighing 15–20 kg, will be required; its cost can reach several tens of thousands of rubles. Household RCDs are designed for different leakage currents (10 and 30 mA). It is best to use one RCD with a high leakage current to connect and protect the entire apartment, additionally supplying individual power lines in the bathroom with several smaller RCDs (for example, one for a washing machine, another for a socket, a third for a lighting line).
Bathroom sockets are in the collections of almost all manufacturers of electrical installation products. So, for example, in the Jung Schuko line, there is a model with a hinged lid (with a return spring) and protection against contact with conductive elements. And when using an additional sealing membrane, the degree of protection IP 44 is achieved. Sockets must be connected via a three-core cable, a single-core cable is also laid for additional potential equalization (safety requirement for rooms with high humidity). The device is grounded by the third conductor of the cable (yellow-green), which is connected to the grounding contact of the mechanism. It is not safe to use two-wire cabling in bathrooms.
Leading Design Engineer of Building Automation Systems, Viart Lighting Company