NF C 15-100 standard applied to the bathroom

Why specific bathroom regulations?

The bathroom poses particular electrical risks due to the constant presence of water and humidity. A wet human body has a considerably reduced electrical resistance, multiplying the dangers in the event of contact with a live element. An electric shock that would be harmless in a dry environment can be lethal in a bathroom.

Standard NF C 15-100 defines precise rules for limiting these risks. It establishes a system of safety volumes around water points (bath, shower, washbasin) where electrical installations are either prohibited or strictly regulated. This graduated approach allows us to adapt the level of protection to the proximity of the water and therefore to the level of danger.

Safety volumes: understanding bathroom zoning

The fundamental principle of the standard is based on the definition of four distinct zones around water points. Each volume imposes specific constraints on authorized electrical equipment.

Volume 0: the submerged zone

Volume 0 corresponds to the interior of the bathtub or shower tray. This is the area of highest risk where water is directly present. No mains-powered electrical equipment is permitted. Only devices operating on safety extra-low voltage (SELV 12V) with a transformer located outside this volume may be installed there.

Volume 1: over the bath or shower

Volume 1 extends vertically above Volume 0, up to a height of 2.25 meters. For a shower without a tray, this volume has a cylindrical shape with a radius of 1.20 meters around the shower head. In this zone, constraints remain very strict. Connection boxes, sockets and switches are not permitted. Only certain equipment dedicated to the bathroom and protected against splashing water (minimum IPX4 rating) may be installed there.

Volume 2: The enhanced security zone

Volume 2 extends 60 centimetres around Volume 1, again up to a height of 2.25 metres. This zone accepts more equipment, but only under strict conditions. Class II luminaires, protected heaters and specific equipment can be installed here. The IPX4 protection rating remains mandatory for equipment exposed to splashing water.

Volume 3 and other volumes

Volume 3, which used to extend 2.40 meters from Volume 2, has been removed in the latest versions of the standard. Beyond volume 2, we find ourselves in a "non-volume" zone, where conventional electrical installations are authorized, provided they are protected by a 30 mA residual current device.

Electrical equipment authorized by volume

In volume 0

As previously stated, only 12V SELV equipment may be installed, and the safety transformer must be located outside volume 0. Some underwater lighting systems for spa baths use this principle.

In volume 1

Authorized equipment is limited to the following items:

• Splash-protected instantaneous water heaters or storage tanks (IPX4)
• Class II luminaires with minimum IPX4
• SELV circuit switches (12V maximum)
• Electric flush mechanisms

All equipment must be supplied individually from the electrical panel, without a junction box in the room.

In volume 2

The possibilities expand in this volume:

• Class II luminaires with IPX4
• Class II heaters
• Shaver sockets with built-in isolating transformer (specific 20V-50V socket)
• Mechanical fans
• Switches and sockets under certain conditions

Conventional 16A sockets remain prohibited in volume 2. Only standardized shaver plugs are authorized, as they incorporate an isolating transformer that galvanically isolates the appliance from the mains.

Out of volume

Outside the defined volumes, electrical installations can be carried out normally. You can install standard sockets, switches and light fittings, with no particular protection rating constraints. However, the entire bathroom installation must be protected by one or more 30 mA residual current devices from the electrical panel.

30 mA residual current protection: an absolute must

The entire bathroom electrical system must be protected by one or more 30 mA differential switches. This device detects current leaks to earth and automatically cuts off the power supply in the event of an insulation fault or accidental contact. The threshold of 30 milliamperes corresponds to the maximum intensity a human body can withstand without risk of cardiac fibrillation.

For a bathroom, we generally recommend dedicating a specific circuit protected by its own differential. This configuration prevents a fault in the bathroom from cutting off power to other important circuits in the home. Type A or AC [differential switches](https://domeashop.com) are suitable for this purpose, with type A being preferable if you have electronic devices with drives.

Local equipotential bonding: additional protection

Beyond the 30 mA differential, standard NF C 15-100 requires a local equipotential bonding (LEL) in the bathroom. This device electrically connects all the metal masses in the room: water pipes, heating pipes, metal frames, metal bathtub bodies, etc.

This equipotential bonding is connected to the system's main earth terminal. It uses a copper conductor with a minimum cross-section of 2.5 mm² for main connections and 1.5 mm² for connections to the various elements. The aim is to ensure that no potential difference arises between two simultaneously accessible metal grounds, even in the event of an insulation fault.

Sockets and switches: locations and constraints

16A sockets

Conventional 16A sockets are not permitted in volumes 0, 1 and 2. They can only be installed outside these zones, i.e. more than 60 centimetres from the outer edge of the bath or shower. In practical terms, this means you can't plug in your hairdryer right next to the sink if it's located near the shower.

To overcome this constraint, it's a good idea to design the bathroom with an area far enough away from water points to accommodate the sockets needed for everyday electrical appliances. An outlet near the mirror, away from the volume, is a practical solution for hairdressing and grooming appliances.

The standard requires at least one 16A socket outlet in the bathroom. In practice, providing two or three sockets considerably improves comfort of use without compromising safety, provided that regulatory distances are respected.

Special shaver socket

As a notable exception, the shaver socket with isolating transformer can be installed in volume 2. This particular plug delivers a voltage of between 20 and 50 volts AC, and incorporates an isolating transformer to galvanically isolate the device from the mains. It is easily recognized by its unique shape, different from standard plugs, which prevents the connection of non-compliant devices.

These [specific sockets](https://domeashop.com) are often still useful near the mirror to plug in an electric shaver or a small electric toothbrush, without having to go as far as the non-volume area.

Switches

Light switches can be installed in volume 2, but must comply with IPX4 protection. In practice, many electricians prefer to position them outside the volume to avoid constraints and simplify installation. Switches installed outside volumes do not require special protection against splashing water.

A modern alternative is to use presence detectors for bathroom lighting, installed outside the room. This solution improves comfort while simplifying compliance with the standard.

Bathroom lighting: solutions and constraints

Lighting is an essential element of comfort and safety in the bathroom. The NF C 15-100 standard strictly regulates luminaires according to their location.

Luminaires in volumes 1 and 2

Luminaires installed in volumes 1 and 2 must be Class II (double-insulated) and have a minimum IPX4 protection rating against splashing water. Class II means that the luminaire has double insulation to protect against indirect contact, even in the event of an insulation fault.

Waterproof LED recessed spotlights are a common and effective solution for illuminating showers and bathtubs. These [specific luminaires](https://domeashop.com) incorporate the necessary protection and offer high-performance lighting with low energy consumption.

Non-volume lighting

Outside regulated volumes, standard luminaires can be installed without any particular sealing constraints. You can use conventional wall lights, ceiling lights or standard recessed spotlights. Nevertheless, given the ambient humidity in a bathroom, it's still a good idea to choose moisture-resistant fixtures, even in non-volume versions.

Electric heating: radiators and towel rails

Electric bathroom heating also obeys the rules of volume. Electric radiators and towel rails can only be installed in volume 2 or outside volumes, never in volumes 0 and 1.

Installation in volume 2

A towel warmer can be installed in volume 2 provided several requirements are met:

• Be Class II (double-insulated)
• Minimum IPX4 protection rating
• Permanently fixed (no electrical outlet, direct connection)

Modern [electric towel rails](https://domeashop.com) generally meet these requirements and are designed specifically for bathroom use. They incorporate the necessary protection, and their Class II design eliminates the risk of indirect contact with live parts.

Non-volume installation

Outside volumes, constraints are becoming more flexible. A standard electric radiator can be installed, although we recommend choosing a model that is resistant to ambient humidity. Heating power must be adapted to the volume of the room to guarantee optimum thermal comfort.

Connection boxes and cable management

Standard NF C 15-100 expressly prohibits junction boxes and junction boxes in volumes 0 and 1. This rule requires that each piece of equipment in these volumes be supplied directly from the electrical panel or from a junction box located outside the volume.

Cables supplying equipment in volumes 1 and 2 should preferably be routed inside walls (recessed) to limit the risk of accidental contact. If a visible passage is unavoidable, the cables must be protected by suitable [insulating conduits](https://domeashop.com).

Cable cross-sections must be sized according to the power of the devices supplied and the length of the circuit. For lighting, a 1.5 mm² cross-section is generally sufficient. A 2.5 mm² cross-section is standard for socket and heating circuits.

Controlled mechanical ventilation

A CMV or air extractor can be installed in the bathroom under certain conditions. In volumes 1 and 2, only Class II systems with IPX4 are permitted. The ventilation motor must be located outside or in an adjacent technical room.

Good bathroom ventilation contributes significantly to the durability of electrical installations by limiting condensation and ambient humidity, which can damage electrical equipment and connections.

Common mistakes to avoid

A number of mistakes are frequently made when installing bathroom wiring, even in recent renovations.

Installation of sockets in prohibited areas

The most common mistake is to install a conventional socket too close to the shower or bathtub, in volume 2. This configuration, although practical, is non-compliant and dangerous. During a Consuel inspection or property sale, this non-conformity will be noted and must be corrected.

Absence or inadequacy of equipotential bonding

Another common mistake, especially in renovation work, is forgetting to include the local equipotential bonding. Yet this protection is essential and mandatory. All conductive metal parts in the bathroom must be interconnected and earthed.

Use of unsuitable equipment

Installing a non-waterproof standard luminaire in a shower, even if it "doesn't receive water directly", is a violation of the standard and a real risk. All equipment must have the protection ratings required for its location, without exception.

No 30 mA differential

In older installations, the bathroom may not be protected by a 30 mA differential switch. This situation does not comply with current standards and presents a mortal danger. The installation of a 30 mA differential should be considered a priority.

Renovation and compliance

When renovating a bathroom, electrical compliance with NF C 15-100 is not always legally required for the entire installation, except in the case of a total renovation or if the installation presents an immediate danger. Nevertheless, taking advantage of the work to bring the electrical installation up to standard is a wise investment for the safety of occupants and the value of the property.

Priority points to check and correct during renovation :

• 30 mA differential protection for all bathroom circuits
• Compliance with safety volumes for existing equipment
• Presence and correct connection of the local equipotential bonding system
• Condition and cross-section of power cables
• IP ratings for luminaires and equipment

An electrical diagnosis carried out by a qualified professional can identify exactly what work is needed to achieve compliance.

Conclusion

The NF C 15-100 standard applied to the bathroom may seem restrictive, but it's the result of decades of feedback on domestic electrical accidents. Compliance with these regulations guarantees safe installation for all occupants, and avoids the risk of electric shock or electrocution in this high-risk area.

The basic principles to remember are simple: keep electrical equipment away from water points in accordance with defined volumes, protect the entire installation with a 30 mA differential, create a complete equipotential bonding system, and use only suitable equipment with the required protection ratings.

Whether you do the work yourself or call in a professional, understanding these rules will help you design a bathroom that's functional, comfortable and perfectly safe. Don't hesitate to consult a qualified electrician if in doubt, as electrical safety takes no guesses.