How to choose a main circuit breaker That's right for your electrical system

Which device serves as the main circuit breaker for the home?

The meter, the service breaker, and the circuit breakers in the panel look alike. However, they do not play the same role. Circuit breakers are classified based on what they protect: the entire home or a single circuit, and whether they protect against overcurrent or ground faults.

Identifying the service circuit breaker

In a residential unit, the term “main circuit breaker” generally refers to the service breaker, also known as the main breaker. It is installed between the utility connection and your indoor electrical system. In practice, if it is positioned to serve this purpose, it is the one that cuts off power to the entire home with a single action.

• Main circuit breaker: Located at the beginning of the electrical system, it protects the entire home.
• Branch circuit breaker: It protects a single circuit in the distribution panel against overloads and short circuits.
• Smart meter: It measures energy consumption and can cut off the power supply if the contracted power limit is exceeded; it should not be confused with a circuit breaker.
• Electrical panel: Located downstream from the service connection, it distributes the circuits and houses their protective devices.

For the same role, the models differ significantly. DomeaShop offers branch circuit breakers that differ in their rating, number of poles, and whether or not they include built-in ground-fault protection. These three criteria form the basis of theSelecting a service circuit breaker.

Distinguishing between fault protection mechanisms

The branch circuit breaker primarily protects against overcurrent. It can also include a 500 mA residual current device (RCD), which detects a current leak by comparing the incoming current to the outgoing current. In the panel, a ground-fault circuit interrupter (GFCI) provides both overcurrent protection and ground-fault protection. Conversely, a residual current device (RCD) only provides the second function: it does not replace the circuit breaker.

The 500 mA differential rating of the connection does not eliminate the need for the 30 mA devices in the distribution panel, known as high-sensitivity devices. According to Promotelec (an association that promotes electrical safety in homes), the NF C 15-100 (French standard for low-voltage electrical installations) requires at least two per dwelling. Divide the circuits among them so that if one trips, it won't cut off power to the entire house.

Check that people are protected

In residential buildings, the TT system (in which the grid neutral and the building's ground potentials are connected to two separate grounding points) combines a grounding connection, a protective conductor, and a residual current device. These elements are not interchangeable. Promotelec uses a ground resistance of less than 100 Ω as a benchmark for a 500 mA residual current: have this value measured before assessing the safety of your electrical system.

Compliance also depends on the edition of the standard. The NF C 15-100 standard, revised in 2024, applies to new construction projects and renovations subject to this standard as of september 1, 2025. It reinforces the requirement to use type F outlets for certain devices with single-phase variable-speed drives: depending on the home’s layout, this requirement may apply to the circuit for a heat pump or an air conditioning unit.

Which caliber should you choose based on the subscribed power?

The rating is measured in amperes and corresponds to the contracted power—that is, the power specified in your contract with your provider. Choosing the right circuit breaker therefore depends first on an assessment of your electricity usage and then on the type of power supply to your home.

Estimate the actual power required

Make a list of appliances that might be running at the same time: heating, hot water, cooking, air conditioning, and charging an electric vehicle. Their simultaneous occurrence matters more than the sum of all installed capacities. An oven and a stovetop used together on a winter evening, with the heat on, take up more space than appliances that are rarely used.

This peak in consumption is then reflected in the size. For single-phase systems, Enedis provides standard correspondences between the contracted power and the circuit breaker's rated current.

The contracted power cannot exceed the connection capacity, which is a technical specification of the grid connection. The Enedis standard dated march 24, 2025, sets a maximum of 12 kVA for single-phase residential connections up to 36 kVA. In a three-phase system, the maximum capacity is 36 kVA, or 12 kVA per phase.

Consider whether the power supply is single-phase or three-phase

The type of power source affects the gauge reading. In a single-phase system, the nominal voltage is 230 V between phase and neutral, and all the power flows through a single phase. In a three-phase system, the voltage between phases reaches 400 V, and the loads are distributed across three conductors.

• Promotelec example: A 12 kVA three-phase service limits the current on each phase to 20 A.
• SéQuélec example: A three-phase power rating of 18 kVA corresponds to 30 A per phase.
• Typical use: Three-phase power meets the needs of equipment designed for this type of power supply.
• Constraint: It requires monitoring the load balance between phases.

These examples show that 12 kVA of three-phase power is not available on each of the three phases. A high-power appliance plugged into a circuit that is already under load can cause a circuit breaker to trip, even if the service capacity appears to be sufficient.

Unless equipment requires three-phase power, single-phase power generally simplifies installation. The difference comes down to the type of appliances you have and the power output required: check their nameplates before deciding on one or the other.

Compare settings and compatible models

The hardware gauge does not always indicate the actual setting. SéQuélec specifies a 9 kVA single-phase connection set to 45 A on a 15–45 A circuit breaker—that is, set to its maximum rating. So be sure to note the setting on your circuit breaker—not just the rating engraved on the front panel.

For a single-phase installation, DomeaShop offers the Legrand 401003, aselective residual-current double-pole circuit breaker 45 A and 500 mA, for flush mounting on 4 modules. For three-phase power, the Legrand 401015 is afour-pole non-ground-fault circuit interrupter 60 A, which disconnects the neutral and occupies 6.5 modules.

How can i safely change the gauge?

Changing the gauge isn't just a matter of turning a knob. An increase in power affects the entire downstream system, and any work on the connection is the responsibility of Enedis.

Check the installation before submitting the request

Start by taking a reading: type of connection, contracted power, visible rating and setting of the circuit breaker, and then the distance and characteristics of the connection to the panel. The cross-sectional area of this cable depends on its length and the allowable voltage drop. In Promotelec's single-phase copper panel, the maximum length is 22 m for 10 mm² at 45 A, and 27 m for 16 mm² at 60 A.

• Downstream installation: the cable, electrical panel, residual current devices, and grounding must be able to handle the increased load; otherwise, the conductors will remain inadequately protected.
• Photovoltaic generation: According to Promotelec, a 60-A AGCP (general control and protection device) and 3 kwp of generation—equivalent to approximately 15 A—can expose certain parts to 75 A.
• Outbuilding or workshop: When connecting from the main house, you must check the length, power rating, upstream protection, voltage drop, grounding, and any subpanel.

The Promotelec lengths are based on the assumptions in its table and are not a substitute for a calculation tailored to the specific project. Depending on the level of protection you need, have an electrician perform this calculation, especially if the service breaker is located far from the panel.

Request the change from the appropriate parties

Once you have completed the checks, submit the request to change your power rating to your electricity provider. The customer contacts Enedis if work needs to be done on the service connection. The homeowner does not adjust or replace the service breaker himself.

With a smart meter, exceeding the power limit can cause a power outage and trigger the "POWER limit EXCEEDED" message. In addition, a simple change in power rating does not always require physically replacing the circuit breaker: adjusting the setting may be sufficient.

Estimate costs and timelines

The Enedis service catalog effective as of august 1, 2025, sets €43.57, including tax, for a change of up to 36 kVA through a simple adjustment. The total comes to €64.87 (including tax) when the circuit breaker needs to be replaced. In both cases, the standard processing time is 10 business days.

These amounts cover the cost of work performed on the service connection. They do not include work to modify the interior electrical system performed by an electrician, such as rewiring or modifying the distribution panel.