The home electrical panel: components, fuses and sizing
The electrical panel is the “brain” of a home’s electrical installation: it receives the energy brought in by the electrical connection (bransament), distributes it across separate circuits and protects both the installation and people against overcurrents, short circuits and electrocution. A well-designed and correctly sized panel reduces the risk of fire, avoids unjustified trips and allows future expansions without any hassle. In this guide we explain the essential components, the role of the fuses and the RCD, as well as the sizing principles we apply at SUN WATT SRL, a company certified by ANRE for design and execution.
What the electrical panel is and where it is installed
The electrical panel (or distribution board) is the enclosure where the protection and control devices of the internal installation are concentrated. It sits downstream of the measurement and protection block (BMP) installed at the property boundary as part of the connection, and it marks the border between the distribution operator’s network and your private installation.
The distribution operator for Bucharest, Ilfov and Giurgiu is Retele Electrice Romania S.A. (formerly E-Distributie Muntenia / Enel, part of the PPC group). It is responsible for the network up to the delimitation point; from the electrical panel onwards, responsibility lies with the owner, and the works must be carried out by authorised electricians.
The panel is usually installed in a dry, ventilated and easily accessible spot (hallway, utility cupboard, stairwell), at a height that allows comfortable operation of the switches. Heat-resistant enclosures are used, fitted with a DIN rail on which all devices are clipped in modular fashion.
The components of a home electrical panel
A modern panel contains several categories of equipment, each with a clear role:
1. The main switch
This is the device that allows the entire home to be de-energised with a single operation. On a single-phase connection it is two-pole (live + neutral), while on a three-phase one (400V) it is four-pole.
2. The miniature circuit breakers (MCBs)
These replace the old fuse wire. They protect each circuit against overload (excessive consumption) and against short circuit. They are chosen according to the rated current (for example 10A, 16A, 20A, 25A) and the cross-section of the conductor.
3. The residual-current device (the 30 mA protection)
The RCD (or residual current device) is the component that saves lives: it detects current leakage to earth and trips within a few milliseconds, before a dangerous current can pass through the human body. For homes, an RCD with a sensitivity of 30 mA is used. There is also a combined version (residual-current circuit breaker, RCBO), which brings short-circuit protection and residual-current protection together in a single module.
4. Surge protection (SPD)
Recommended especially in areas with frequent atmospheric discharges or for homes with sensitive electronic equipment. It diverts transient overvoltages to earth.
5. The neutral bar and the protective bar (PE)
The connection points for the neutral conductors and, respectively, the earthing conductors. The PE bar must be correctly connected to the earthing system, whose value is checked through PRAM measurements.
6. The connecting conductors and the labels
Correctly sized cables and clear labelling of each circuit, essential for fast and safe interventions.
The difference between a miniature circuit breaker and an RCD
Many owners confuse them, but the two protections are complementary and mandatory together:
| Feature | Miniature circuit breaker (MCB) | Residual-current device (RCD) |
|---|---|---|
| What it protects | The installation and the circuits | People (electrocution) |
| What it reacts to | Overload and short circuit | Fault current to earth |
| Typical home threshold | 10A / 16A / 20A / 25A | 30 mA |
| Tripping time | Milliseconds - seconds | Under 30 ms |
| Mandatory | Yes, on every circuit | Yes, on groups of circuits |
The practical conclusion: the MCB prevents fires, while the RCD prevents electrocution. A panel without a 30 mA RCD is not safe, no matter how many breakers it has.
Sizing the circuits and the panel
Sizing starts from the power available through the connection and from the number of consumers. A single-phase connection usually provides around 11 kW, sufficient for an ordinary home, while a three-phase connection (400V) is recommended for large houses, with heat pumps, EV charging or workshops.
The basic principle: each group of consumers gets its own circuit, with a fuse and cable cross-section adapted to it. Here are indicative values used in practice:
| Circuit | Cable cross-section (copper) | Miniature circuit breaker |
|---|---|---|
| Lighting | 1.5 mm² | 10A |
| General-purpose sockets | 2.5 mm² | 16A |
| Kitchen / electric hob sockets | 2.5-4 mm² | 16-20A |
| Washing machine / water heater | 2.5 mm² | 16A |
| Air conditioning | 2.5 mm² | 16A |
| Hob / electric oven | 4-6 mm² | 25-32A |
| Boiler / heat pump | dedicated sizing | according to power |
| EV charging (wallbox) | dedicated sizing | according to power |
For an average home with a single-phase connection, 8-12 circuits are usually sufficient. For three-phase, 12-24 modules are recommended, with consumption balanced across the three phases to avoid uneven loading.
When sizing, reserves are also taken into account: it is recommended to provide free space in the panel (20-30%) for future circuits, without needing to replace the enclosure.
Common mistakes to avoid
- The absence of an RCD or the use of one with a sensitivity that is too high (above 30 mA for socket circuits).
- Undersizing the cables relative to the chosen fuse (a 1.5 mm² cable protected by a 20A breaker - a fire hazard).
- Overloading a single circuit with too many high-power consumers.
- Deficient earthing - without a correct earthing system, the residual-current protection and the surge protection do not work optimally.
- An unlabelled panel, difficult to troubleshoot in case of a fault.
How the panel connects to the connection
The electrical panel is part of the internal installation and is installed after the connection is made and the technical connection approval (ATR) is obtained. The correct flow is: dossier and connection project, execution of the connection by an ANRE-certified company, installation of the panel and the internal installation, then the checks (including the PRAM measurements and the verification of the earthing system).
At SUN WATT SRL we offer both the execution of the connection and the design and installation of the panel and the internal installation, with the issuing of the necessary documents. Indicative prices: single-phase connection from 1,800 lei, three-phase from 2,900 lei, underground connection from 3,500 lei, dossier and connection project from 900 lei, earthing system from 900 lei, PRAM verification from 250 lei. The final price is set according to the solution approved through the ATR.
See the full list in the prices section, estimate the cost with the help of the connection cost calculator or describe your situation to us via the contact page. Phone: 0733 097 440.
Conclusion
A correctly designed electrical panel means: a main switch, a 30 mA RCD, miniature circuit breakers adapted to each circuit, cables with an appropriate cross-section and a verified earthing. Sizing starts from the connection’s power (single-phase ~11 kW or three-phase 400V) and from the number of consumers, with a reserve for the future. For a safe and compliant installation, leave the design and the installation to ANRE-certified electricians.