What is the maximum number of luminaires per circuit breaker?

The basic rules of standard NF C 15-100

The French electrical standard NF C 15-100 precisely defines the characteristics of lighting circuits. Contrary to popular belief, it's not so much the number of luminaires that counts, but the total power of the circuit and its appropriate protection.

The lighting circuit principle

A lighting circuit is made up of all the light points supplied by the same circuit breaker. The standard imposes strict limits to guarantee safety:

For a circuit protected by a 16A circuit breaker with a 1.5 mm² cable cross-section (the standard configuration), you can install up to 8 maximum lighting points. This limitation applies regardless of the wattage of the luminaires, as long as the maximum power of the circuit is not exceeded.

For a circuit protected by a 10A circuit breaker with a cable cross-section of 1.5 mm², the standard also authorizes up to 8 lighting points. Although the circuit-breaker is smaller, the number of points remains the same, as the cable cross-section is the main limiting factor.

The notion of a lighting point

A lighting point corresponds to a DCL (Device de Connexion Luminaire) socket or a cable outlet designed to supply one or more luminaires. Important: if you install a ceiling light with 5 bulbs, this counts as a single light point, not five.

This distinction is crucial to the calculation. A 10-branch chandelier connected to a single cable outlet = 1 lighting point. On the other hand, 5 independent recessed spotlights with 5 different cable outlets = 5 lighting points.

Calculating the maximum power of a lighting circuit

Beyond the number of points, total power remains the decisive criterion for system safety.

Power calculation formula

The maximum power of a circuit is calculated according to the formula: P = U × I.

Where:

• P = Power in watts (W)
• U = Voltage in volts (V) - 230V in France
• I = Current in amperes (A)

For a 16A circuit breaker: 230V × 16A = 3680 watts maximum.

For a 10A circuit breaker: 230V × 10A = 2300 watts maximum.

Practical application with different luminaire types

Let's look at some concrete examples to illustrate these calculations:

Scenario 1 - Modern LED lighting :

8 LED ceiling lights, 15W each = 120W total. You're well below the 3680W limit with a 16A circuit breaker. In this case, it's the number of points (8 maximum) that constitutes the limit, not the power.

Scenario 2 - Old halogen lighting :

8 halogen spotlights of 50W each = 400W total. Still in line with 16A, but consumption is much higher.

Scenario 3 - Intensive mixed lighting :

If you install 6 lighting points with powerful luminaires totalling 3,500W, you comply with both the limit on the number of points (6 < 8) and the power limit (3500W < 3680W).

Problematic scenario:.

4 halogen spotlights of 1000W each = 4000W. Even if you don't exceed 8 points, you exceed the maximum power rating of the 16A circuit-breaker (3680W). This is a dangerous installation.

Cable cross-sections and their importance

The choice of cable cross-section has a direct influence on the number of luminaires that can be installed, and on the safety of the installation.

Standard 1.5 mm² cross-section

This is the minimum and most commonly used cross-section for domestic lighting circuits. It enables :

• Protection by 10A or 16A circuit breaker
• Maximum 8 lighting points
• Circuit length up to 40-50 meters with no problematic voltage drop

2.5 mm² cross-section

Rarely used for domestic lighting, it may be necessary in certain specific cases:

• Very long circuits (over 50 metres)
• High-power lighting for business premises
• Protection by 20A circuit breaker possible

This section offers better resistance to voltage drop, but remains exceptional for simple residential lighting circuits.

Voltage drop and circuit length

Voltage drop is a physical phenomenon that reduces the voltage at the end of the line. The standard requires a maximum voltage drop of 3% for lighting circuits. Beyond a certain length, you need to either increase the cable cross-section or create a new circuit.

For a 1.5 mm² cross-section and a 16A circuit-breaker, the maximum recommended length is around 40 meters, to stay within acceptable voltage drop limits.

Intelligent distribution of lighting circuits

A well-designed installation not only complies with legal maximums, it also anticipates needs and optimizes distribution.

Division by functional zones

Day zone: It's a good idea to create a dedicated circuit grouping together the living room, dining room and kitchen. With modern LED lighting, these 3 rooms can often share a 16A circuit without any problem.

Night zone: Bedrooms and night corridor can form a second circuit. Room lighting is generally energy-efficient, allowing 3-4 rooms to be grouped on the same circuit.

Sanitary and outdoor: Bathrooms and toilets often deserve a separate circuit, as does outdoor lighting, which may have specific needs.

Recommended number of circuits according to surface area

The NF C 15-100 standard requires a minimum number of circuits depending on the surface area:

• Dwelling = 35 m²: minimum 2 lighting circuits

• Dwelling from 35 to 100 m²: minimum 3 lighting circuits

• Dwelling > 100 m²: minimum 4 lighting circuits

These minimums ensure that a failure on one circuit does not plunge the whole dwelling into darkness.

Anticipating future developments

When designing an installation, it is wise to allow for margins:

1 Don't systematically use all 8 stitches if you don't need to.

2 A circuit with only 5-6 points makes it easy to add a luminaire at a later date.

3 Installing additional circuits during construction work costs little but offers great flexibility

Special cases and exceptions

Certain situations require specific attention or adaptations to these general rules.

Extra-high-power luminaires

Exterior spotlights, some workshop lighting and stage lighting systems can consume several hundred watts per point. In this case :

• First calculate the total power
• Check that you are not exceeding the maximum power rating of the circuit breaker.
• Consider dedicated circuits for large consumers
• If necessary, use larger circuit breakers with suitable cable cross-sections.

Dimmable lighting (dimmers)

Dimmers introduce harmonics into the power grid. It is recommended to :

• Do not overload a circuit equipped with inverters
• Limit to 5-6 points maximum on a circuit with variation
• Use dimmers compatible with the type of luminaire (LED, halogen, etc.).)

Mixed lighting and socket circuits

The standard strictly prohibits mixing lighting and sockets on the same circuit. Each type of use must have its own dedicated circuits with appropriate protection:

• Lighting circuits: 10A or 16A circuit breaker, 1.5 mm² cross-section
• Socket circuits: 16A or 20A circuit breaker, 2.5 mm² cross-section

This separation ensures that a short-circuit on one socket does not cut off the lighting and vice versa.

Specific premises (garage, cellar, outside)

These spaces often require dedicated circuits:

Garage and cellar: Although part of the home, it's best to create a specific circuit, especially if you're installing powerful task lighting there.

Exterior lighting: Exterior lighting fixtures must be protected by a 30 mA differential device. A dedicated circuit facilitates this protection and makes it easy to isolate the exterior if necessary.

Lighting technologies and their impact on sizing

The technological evolution of luminaires has profoundly altered sizing issues.

Transition to LED

LED bulbs have revolutionized home lighting:

• A 10W LED offers the equivalent of an old 60W bulb
• Consumption of a complete LED lighting circuit rarely exceeds 200-300W
• The number of points becomes the limiting factor, not the power.

This evolution means that in most modern installations, you'll reach the 8-point limit well before the breaker's power limit.

Consumption comparison

To light a 25 m² living room:

Halogen solution (old):.

• 6 x 50W spotlights = 300W total
• Power used: 300W / 3680W = 8% of circuit capacity

LED solution (modern) :

• 6 x 7W LED spotlights = 42W total
• Power used: 42W / 3680W = 1.1% of circuit capacity

The difference is spectacular. With LEDs, even the most power-hungry installations remain far from the power limit.

Intelligent, connected lighting

Connected lighting systems (smart bulbs) generally consume between 8 and 15W per point. Their impact on sizing is negligible in terms of power, but they may require :

• Stable circuits (no nuisance shutdowns)
• A continuous power supply to maintain the connection
• Sometimes special transformers or power supplies

Common mistakes to avoid

Several mistakes are frequently made when installing lighting circuits.

Oversizing the circuit breaker

Installing a 20A or 32A circuit breaker for a standard lighting circuit is a mistake. The circuit-breaker must protect the cable, not the user. A 1.5 mm² cable can carry no more than 16A. An oversized circuit breaker would not trip in the event of an overload, leaving the cable to heat up dangerously.

Cable cross-section undersizing

Using 1 mm² wire or bell wire to save a few euros is dangerous and non-compliant. The 1.5 mm² cross-section is the absolute minimum for lighting.

Exceeding points without calculation

Adding "just one more spot" to reach 9 or 10 points violates the standard. Beyond 8 points, create a new circuit. It's a question of safety and compliance.

Incorrect circuit distribution

Putting all the lights in your home on a single circuit (even within legal limits) is bad practice. In the event of a problem, the entire dwelling is plunged into darkness. Redundancy is safety.

Neglecting transformer ratings

For low-voltage lighting (12V LEDs in particular), the transformer is often the weak link. A 60W transformer can only supply 60W of LEDs, regardless of the number of points on the upstream 230V circuit.

Practical installation and installation tips

A few best practices are essential for a compliant, long-lasting installation.

Schematics and planning

Before starting any work, draw up a detailed diagram:

• Identify each lighting point
• Calculate total expected power
• Determine the number of circuits required
• Locate the electrical panel and calculate cable lengths

A well-thought-out plan avoids unpleasant surprises and costly modifications.

Marking and locating

On the electrical panel, clearly identify each circuit:

• "Day zone lighting
• "Room lighting"
• "Outdoor lighting

This greatly facilitates future maintenance and troubleshooting.

Safety margins

Rather than exploiting the maximums allowed :

• Limit yourself to 6-7 points per circuit if possible
• Keep 20-30% margin on the calculated power
• Provide additional circuits for large installations

Compliance with color codes

Be sure to follow the color codes for the wires:

• Blue: neutral

• Red, black or brown: phase

• Green/yellow: land

Earthing is mandatory on all lighting circuits, even if some Class II luminaires do not use it.

Conclusion

The maximum number of luminaires per circuit breaker is governed by standard NF C 15-100: 8 lighting points maximum on a circuit protected by a 16A circuit breaker with 1.5 mm² cable cross-section. This limit is accompanied by a total power constraint of 3,680 watts for a 16A and 2,300 watts for a 10A.

With the move towards energy-efficient LED technologies, the number of points is now the main limitation, with total wattage generally well below authorized maximums. A well-designed installation favors the multiplication of circuits rather than concentration on a single one, guaranteeing safety, comfort and scalability.

For any electrical installation, scrupulous compliance with the standard is not just a legal obligation: it's the guarantee of a safe, efficient and long-lasting home. If in doubt, never hesitate to consult a qualified electrician.