What is a branch circuit breaker?

Definition and role of the service circuit breaker

What exactly is a branch circuit breaker?

The service circuit breaker, also known as the subscriber circuit breaker or EDF circuit breaker, is a protection and disconnection device installed at the head of your electrical installation. It is the point of separation between the public electricity distribution network and your private installation. This device generally belongs to the network operator (Enedis in France) and is an integral part of the electricity meter.

Contrary to popular belief, circuit breakers don't just cut off the power in the event of a problem. It performs several vital functions that guarantee the safety of your electrical installation and the protection of people.

The three main functions of the service circuit breaker

1. The overcurrent protection function.

The circuit breaker protects your installation against overloads and short circuits. When the current exceeds the calibrated threshold (generally between 15A and 90A, depending on your subscription), the circuit breaker automatically trips and cuts off the power supply. This protection prevents cables from overheating and causing a fire.

2. The general cut-off function.

The branch circuit breaker cuts off the power supply to your entire home simply by operating its lever. This function is essential when working on the electrical installation, in an emergency, or when you're away for a long time. It's the only device that lets you switch off your entire installation from a single point.

3. The power limit function.

The connection circuit-breaker regulates the maximum power you can draw from the grid according to your contract. If you exceed the contracted power by using too many appliances simultaneously, the circuit breaker trips. This function protects the distribution network and ensures that you comply with the terms of your contract with your electricity supplier.

Location and composition of the service circuit breaker

Where is the branch circuit breaker located?

The connection circuit-breaker is systematically installed in the technical housing duct (GTL) or in the control panel, just after the electricity meter. It is the first protective element you encounter on your installation. In older homes, it may be located in a wall-mounted electrical cabinet, while in newer buildings, it is integrated into a complete box containing meter and protection.

The location of the circuit breaker is governed by standard NF C 14-100, which stipulates that it must be easily accessible, located between 0.90 m and 1.80 m above the ground, and protected from the weather if installed outdoors.

Components of a branch circuit breaker

A branch circuit breaker consists of several technical components:

The housing: usually made of shock- and flame-resistant insulating material, it protects internal components and ensures user safety.

The tripping mechanism: this comprises a thermal release (bimetallic strip) which reacts to prolonged overloads, and a magnetic release (coil) which intervenes rapidly in the event of a short-circuit.

Contacts: these are conductive elements that open or close to establish or interrupt current flow. They are sized to withstand the current rating of the circuit-breaker.

The control lever: located on the front panel, it allows manual operation of the circuit-breaker and visually indicates its status (open or closed).

Connection terminals: for connecting incoming (network) and outgoing (installation) cables.

Technical operation of the service circuit breaker

The operating principle

The circuit breaker operates on the principle of detecting electrical anomalies. It constantly monitors the current flowing through it. As long as this current remains within the normal limits defined by the circuit-breaker rating, the device remains closed and allows the current to flow.

When an anomaly is detected, two types of triggers can intervene depending on the nature of the problem:

The thermal trip: This uses a bimetallic strip (two metals joined together with different coefficients of expansion) which deforms under the effect of the heat produced by an overcurrent. When the deformation reaches a critical threshold, it activates the trigger mechanism. This system reacts with a certain delay, which is normal for a progressive overload.

The magnetic trip unit: This uses an electromagnetic coil to create a magnetic field proportional to the current intensity. In the event of a short-circuit (very high current), the magnetic field becomes strong enough to attract a metal core, which instantly opens the contacts. This triggering is virtually instantaneous (a few milliseconds).

The trigger curve

Branch circuit breakers follow standardized tripping curves that define their response time as a function of current intensity. The most common curve for domestic circuit breakers is curve C, which offers a good compromise between tolerance to appliance start-up currents and rapid intervention in the event of a fault.

A typical trigger curve shows that :

- For a 13% overload (1.13 times rated current), the circuit-breaker can remain closed indefinitely.

- At 45% overload (1.45 times rated current), tripping occurs in less than an hour.

- In the event of a short-circuit (5 to 10 times the rated current), tripping is instantaneous.

The different types of circuit breaker

Size classification

The rating of a branch circuit breaker corresponds to the maximum current it can permanently withstand. This rating is determined by the power you subscribe to with your electricity supplier.

Circuit breaker 15/45A (single-phase) : suitable for small installations with a subscribed power of 3 to 9 kVA. It can be found in studios, small apartments or second homes.

30/60A circuit breaker (single-phase): the most common in homes, it corresponds to a power rating of 6 to 12 kVA, i.e. the majority of single-family homes and apartments.

60/90A circuit breaker (three-phase or single-phase) : for larger installations requiring 12 to 18 kVA, such as large houses, homes with electric heating or business premises.

Circuit breaker over 90A: reserved for industrial installations or very large homes with high energy requirements.

Classification by number of phases

Single-phase circuit breaker: protects a 230V installation with two active conductors (phase and neutral). This is the most common type in recent homes. Maximum single-phase power is generally limited to 18 kVA.

Three-phase circuit breaker: protects a 400V installation with four conductors (three phases and one neutral). This type of installation was common in older buildings and is still used when the power required exceeds 18 kVA or to supply specific three-phase appliances.

Selective branch circuit breakers

Selective branch circuit breakers (type S) are designed to provide better coordination with protection devices downstream of the installation. They have a deliberately delayed tripping time, enabling the divisional circuit-breakers to react first in the event of a localized fault. This selectivity avoids a general shutdown of the installation when only one circuit is faulty, thus improving user comfort.

Branch differential circuit breakers

Some circuit-breakers incorporate 500 mA residual current protection. Although less sensitive than the 30 mA differential switches on the electrical panel, this function provides initial protection against major insulation faults. These models are particularly recommended for older installations which do not always have full downstream residual current protection.

Technical specifications to know

Switching power

The breaking capacity (Icn or Icu) represents the maximum short-circuit current that the circuit-breaker can interrupt without being destroyed. This value, expressed in kilo-amperes (kA), is crucial to safety. Household circuit breakers generally have a breaking capacity of 6 to 15 kA, which is more than sufficient for domestic installations.

Rated voltage

The rated voltage corresponds to the nominal voltage for which the circuit-breaker is designed. In France, single-phase circuit breakers are designed for 230V and three-phase for 400V. This characteristic must correspond to the type of power supply for your installation.

The limitation class

Some circuit-breakers have a limiting class (class 1, 2 or 3) which indicates their ability to limit the energy allowed through in the event of a short-circuit. A limiting circuit-breaker (class 3) provides better protection for downstream equipment by reducing electrodynamic and thermal stresses during faults.

Mechanical and electrical endurance

Mechanical endurance represents the number of operations (opening/closing) the circuit-breaker can perform without an electrical load. Electrical endurance, which is more restrictive, indicates the number of maneuvers possible at rated load. A quality circuit breaker can withstand between 10,000 and 20,000 electrical operations.

Installation and regulations

Who can install a branch circuit breaker?

Installation and replacement of branch circuit breakers are strictly regulated. In France, only the network operator (Enedis or a local authority) or a professional authorized by them is authorized to work on this equipment. The circuit breaker is part of the public domain and remains the property of the network operator.

Unauthorized tampering with the circuit breaker is not only dangerous, it's illegal. It can lead to financial penalties, termination of the electricity supply contract, or even legal action in the event of an accident.

Applicable standards

The installation of the service circuit breaker is governed by several standards:

Norm NF C 14-100: defines low-voltage connection installations between the public distribution network and domestic installations. It specifies the circuit-breaker's technical characteristics, its location and installation conditions.

Standard NF C 15-100: although primarily concerned with indoor installation, it defines the interface with the branch circuit breaker and imposes certain coordination requirements.

NF EN 60898-1: defines the technical characteristics of domestic circuit breakers for overcurrent protection.

Connecting to the electrical panel

The branch circuit breaker is connected to the main switchboard by cables sized according to the subscribed power. These cables, generally made of copper, must comply with minimum cross-sections :

- 10 mm² for ratings up to 45A (single-phase)

- 16 mm² for 60A rating (single-phase)

- 25 mm² for 90A rating (single-phase)

Cable routing must be careful, mechanically protected, and as short as possible to limit line losses and fault risks.

Maintenance and repair

Preventive maintenance operations

Although it is the property of the network operator, certain simple operations can extend the life of your circuit breaker:

Monthly function test: operate the circuit breaker lever once a month to check its mobility and prevent the mechanisms from seizing. This simple procedure keeps the contacts in good condition.

Visual monitoring: regularly inspect the external condition of the circuit breaker. Look for signs of overheating (housing discoloration, burning smell), cracks, or any visible damage. In the event of a fault, contact Enedis immediately.

Tightening check: if you are qualified and authorized, check the tightness of the connections annually. Poor contact can cause localized overheating and damage the circuit-breaker.

Cleaning: keep the circuit-breaker environment clean and dry. Dust and humidity can affect its operation and accelerate degradation.

Understanding nuisance triggers

A branch circuit breaker that regularly trips can have several causes:

Installation overload: you are simultaneously using too many electrical appliances for your subscribed power. Solution: reduce simultaneous consumption or increase your subscription.

Insulation fault: a device or circuit has an insulation fault. Solution: disconnect the devices one by one to identify the culprit, then have it repaired or replaced.

Old age of circuit breaker: after 15 to 20 years of service, a circuit breaker can become too sensitive. Solution: contact Enedis for a replacement.

Short-circuit: a clear fault in the system causes immediate tripping. Solution: call in a qualified electrician to locate and repair the short-circuit.

When should I contact the network operator?

You must contact Enedis in the following situations:

- Circuit breaker does not reset after tripping

- You notice burn marks or overheating on the housing

- Circuit breaker lever is stuck or does not stay in the closed position

- You wish to increase the power of your subscription

- Circuit breaker trips for no apparent reason despite normal power consumption

- You notice a leak (water infiltration)

Branch circuit breaker vs. other protective devices

Difference from divisional circuit breaker

The branch circuit breaker is often confused with the divisional circuit breakers on the electrical panel. Although their operating principle is similar, they perform different roles:

Service circuit breaker :

- Protects the entire system

- High ratings (15 to 90A)

- Property of the network operator

- Installation upstream of the electrical panel

- Limits power according to subscription

Divisional circuit breaker :

- Protects a specific circuit (lighting, sockets, etc.).)

- Lower ratings (2 to 32A)

- Customer property

- Electrical panel installation

- Circuit overload and short-circuit protection

Difference with the differential switch

The differential switch and the circuit breaker are complementary but distinct:

Differential switch :

- Protects against current leakage (electrocution)

- 30 mA sensitivity (high sensitivity)

- Does not protect against overloads

- Detects insulation faults

- Mandatory for modern installations

Service circuit breaker :

- Protects against overcurrent

- Can have 500 mA differential sensitivity (optional)

- Global plant protection

- Power limiting

Difference from electric meter

The meter and the circuit breaker are two separate pieces of equipment that are often grouped together in the same box:

Electric meter :

- Measures energy consumption

- Does not protect the system

- Enables billing

- Cannot cut power (except Linky with remote control)

Service circuit breaker :

- Protects the installation

- Enables manual shutdown

- Does not measure consumption

- Limits available power

How do I choose my branch circuit breaker?

Depending on contract power

Your choice of circuit-breaker rating depends directly on your subscribed power. Here is a general correspondence table:

3 kVA: 15A single-phase circuit breaker (small studio)

6 kVA: 30A single-phase circuit breaker (apartment, small house)

9 kVA: 45A single-phase circuit breaker (medium-sized house)

12 kVA : 60A single-phase circuit breaker (large house)

15 kVA: 75A single-phase or three-phase circuit breaker

18 kVA : 90A single-phase or three-phase circuit breaker

Note that it is the network operator who determines and installs the right circuit breaker for your subscription. You cannot freely choose a larger size without modifying your contract.

Depending on the type of installation

Single-phase installation: preferred in modern homes up to 18 kVA. It offers better load distribution and simpler installation.

Three-phase installation: required above 18 kVA or if you have three-phase equipment (heat pump, industrial motors, etc.).). It spreads the load over three phases, but is more complex to manage.

Additional options

Integrated residual current protection: recommended if your installation does not have a complete 30 mA residual current protection system. It offers basic protection against electric shock.

Selectivity: useful in large installations to avoid unnecessary blackouts. A selective circuit-breaker gives the downstream protection devices time to react first.

Position indicator: very practical for checking circuit-breaker status remotely (particularly useful if the circuit-breaker is far away).

Connection terminal blocks: some models offer more accessible terminal blocks for easier connection and servicing.

Technological evolution of service entrance circuit breakers

Communicating circuit breakers

With the arrival of Linky meters, circuit breakers are also changing. The new models can integrate communication functions allowing :

- Remote reset in the event of overload tripping

- Remote monitoring of circuit-breaker status

- Automatic adaptation of available power to dynamic contracts

- Transmission of information on detected faults

These features enhance user comfort and enable more precise management of power consumption.

Electronic circuit breakers

Electronic circuit breakers represent the new generation of protection. Unlike traditional electromechanical circuit breakers, they use electronic sensors and microprocessors to detect anomalies. Their advantages:

- Increased detection accuracy

- Fine-tuned, customizable settings

- Optimized trigger curves

- Integrated fault diagnosis

- Greater durability (fewer mechanical parts)

- Connectivity and remote supervision

Home automation integration

New-generation branch circuit breakers are gradually being integrated into home energy management systems. They can contact :

- Automatic load shedding systems (temporary shutdown of non-priority devices)

- Energy managers who optimize consumption during off-peak hours

- Mobile applications for real-time monitoring

- Energy production systems (solar panels, batteries) for intelligent management

Economics and sustainability

Cost and lifetime

The cost of a branch circuit breaker varies according to its rating and functionality, from around 150 to 500 euros. However, since it's owned by the network operator, you don't usually have to buy it. Replacement in the event of defects or obsolescence is handled by Enedis as part of its network maintenance.

The average service life of a service circuit breaker is 15 to 25 years, depending on operating conditions and environment. Factors influencing longevity :

- Trigger frequency

- Environmental conditions (temperature, humidity)

- Quality of downstream electrical installation

- Stability of the distribution network

- Regular maintenance

Environmental impact

Manufacturers of circuit breakers are increasingly committed to an eco-responsible approach:

Recyclability: modern circuit breakers are designed to be easily dismantled and recycled at the end of their life. Metals (copper, aluminum) are recovered and recycled.

Energy efficiency: the new electronic circuit breakers consume less energy and generate less heat loss than their predecessors.

Durability: improved reliability and service life reduce replacement frequency and therefore overall environmental impact.

Hazardous substances: European standards (RoHS) limit the use of toxic substances in electrical equipment.

Practical tips to optimize use

Avoid frequent tripping

To reduce the inconvenience caused by tripped circuit breakers:

Size your subscription correctly: analyze your actual consumption and adjust your subscribed power accordingly. An undersized subscription will cause frequent power cuts.

Schedule your consumption: avoid running all your energy-hungry appliances (electric heating, water heater, washing machine, oven, etc.) simultaneously.). A simple timeframe can solve many problems.

Use a load shedder: this device automatically cuts off non-priority circuits when consumption approaches the limit, thus avoiding tripping the branch circuit breaker.

Modernize your equipment: replace old, energy-hungry appliances with recent, energy-efficient models. Overall consumption will drop, reducing the risk of overloading.

Managing a power increase

If you find that your circuit breaker regularly trips despite normal use, it may be time to increase your contract power:

Assess your needs: list all your appliances and their wattages, identify periods of high consumption. This will give you an accurate idea of the power required.

Contact your supplier: to change your subscribed power, contact your electricity supplier, who will forward the request to Enedis.

Check your installation: before increasing power, make sure your electrical installation (switchboard, wiring) can handle the extra load. Upgrading may be necessary.

Anticipate the delays: changing power generally requires the intervention of an Enedis technician to adapt or replace the connection circuit breaker. Allow a few days to a few weeks, depending on availability.

Awareness-raising and training

Inform occupants: make sure everyone in the household knows the location of the branch circuit breaker and how to reset it in the event of a trip.

Explain the limits: make it clear why certain combinations of appliances cause outages, to develop good consumption habits.

Prepare for emergencies: keep emergency numbers (Enedis, electrician, fire department) close to the circuit breaker and a flashlight in case of a night-time power cut.

Conclusion

The circuit breaker is much more than a simple switch: it's the silent guardian of your electrical installation. Understanding it is essential for any owner or tenant concerned about the safety and smooth running of their home. From its overcurrent protection function to its power regulation role and its ability to cut off the general power supply, the service circuit breaker plays a vital role in everyday life.

The technological evolution of these devices, with the integration of communicating and electronic functions, opens up new prospects for even smarter, safer management of our electricity consumption. At a time of energy transition and connected homes, the service circuit breaker is adapting to meet the new challenges of the 21st century.

Although maintenance is the responsibility of the network operator, informed use and regular checks on your part will help extend its service life and guarantee optimum protection. Never hesitate to contact Enedis or a qualified professional in case of doubt or anomaly: electrical safety is never an area where you have to improvise.

By mastering the operating principles and best practices for using your circuit breaker, you can ensure optimum electrical comfort and effective protection for your home. Investing time in this understanding means investing in the safety and tranquillity of your daily life.