Guide

Single-phase or three-phase? Belgian networks and building connections

1×230 V, 3×230 V or 3N~400/230 V: understand the Belgian street network, neutral conductor and connection phase count, and plan protection, EV charger and heat pump accordingly.

Published on 27 July 2026 Updated on 5 October 2026 12 min

AuthorStephan Behm

Short answer: look at the network and the connection separately

In Belgium you decide between single-phase and three-phase in two steps. First you identify the low-voltage network in your street: 230 V without a neutral (3×230 V) or 400/230 V with a neutral (3N~400/230 V). Then you choose the building connection: single-phase or three-phase. Single-phase is enough for many homes; an 11 or 22 kW EV charger or a three-phase large appliance needs a suitable three-phase connection. The grid operator confirms what is available at your address.

“Single-phase = 1×230 V” therefore describes the connection, not the street network. A single-phase 230 V connection is supplied either phase–neutral from a 400/230 V network or phase–phase from a 3×230 V network. ORES states explicitly that a single-phase connection does not always include a neutral conductor.

The four combinations

Street network	Building connection	Conductors at the connection	Technical notation
400/230 V with N	single-phase	L + N	1×230 V, L–N
400/230 V with N	three-phase	L1 + L2 + L3 + N	3N~400/230 V
230 V without N	single-phase	two line conductors	1×230 V, L–L
230 V without N	three-phase	three line conductors	3×230 V without N

How common is 3×230 V?

The 3×230 V network is everyday reality in Belgium. Fluvius still had 18,101 km of 230 V low-voltage network at the end of 2024, mainly in urban and western areas. Sibelga states that around 80% of the Brussels territory is supplied at 230 V. That does not make every Brussels household three-phase: Sibelga gives 9.2 kVA, single-phase 230 V at 40 A, as the standard for an average household.

Power at the same current rating

Available power depends on voltage, number of phases and connection current. For 40 A, ORES lists:

Connection	Apparent power at 40 A
Single-phase 230 V	9.2 kVA
Three-phase 3×230 V	15.9 kVA
Three-phase 3N~400/230 V	27.7 kVA

The calculation: single-phase apparent power is voltage times current (230 V × 40 A ≈ 9.2 kVA). For a balanced three-phase load you multiply line-to-line voltage, current and √3 (230 V × 40 A × 1.73 ≈ 15.9 kVA; 400 V × 40 A × 1.73 ≈ 27.7 kVA). These figures give the technical order of magnitude. Your contracted capacity is set by the connection breaker and the grid operator; the real power an appliance can use also depends on its power factor.

With an unbalanced distribution, each line conductor counts on its own. A large total capacity does not help if many single-phase loads sit on the same phase.

What this means for EV chargers, heat pumps and PV

EV charger: 3.7 or 7.4 kW often works single-phase. 11 or 22 kW normally needs a suitable three-phase connection. Not every charger runs on 3×230 V; Sibelga points out limitations for 11/22 kW charging. Design and obligations are covered in EV chargers and the AREI.
Heat pump and hob: the nameplate decides. An appliance designed for 3N~400 V does not simply run on 3×230 V without a neutral. How to show the heat pump in the diagram is explained in heat pump single-line diagram.
PV: the permitted inverter power and phase distribution are set by the grid operator for the specific connection; there is no single Belgian limit. More in documenting a PV system.

Before buying a large appliance, always check both: single- or three-phase and 230 V without N or 400/230 V with N.

Protection and RCDs on a 3×230 V network

On a 3×230 V network, both active conductors of a 230 V circuit are line conductors. Book 1 of the AREI/RGIE, Belgium's general regulations for electrical installations, requires in subsection 4.4.4.2 overcurrent detection on both active conductors in single-phase and two-phase circuits of domestic installations. Exception: a residual current device at the same level also contains overcurrent detection on one line conductor and disconnects both active conductors. In practice you therefore plan circuit breakers with two protected poles on 3×230 V. For three-phase circuits without a distributed neutral, subsection 4.4.4.3 sets out when one line conductor may remain without its own overcurrent detection.

An RCD does not need a neutral as a “reference”. It compares the currents in all active conductors passing through it. On 3×230 V it therefore measures and switches all line conductors involved together and protects just as effectively as on 3N~400/230 V.

Distributing the phases sensibly

With a three-phase connection, spread the single-phase loads as evenly as possible across the phases. The AREI sets no percentage for this. A warning threshold such as 30% is a design aid, not an AREI requirement. With a single-phase connection there is nothing to distribute. Document the assignment in the board and check it after every change.

How to identify your connection

Look at the meter, the connection breaker and the incoming conductors without opening any parts sealed by the grid operator. ORES shows example photos of single-phase 230 V, 3×230 V and 3×400 V + N. Counting visible wires easily misleads, because the protective conductor, internal wiring or an older installation add to the count. Binding confirmation comes from the grid operator or an electrician.

From load list to connection decision

Draw up a load list before you apply for more capacity. Separate continuous loads, short simultaneous peaks and controllable loads. Hob, heat pump, instantaneous water heater, EV charger and inverter have different profiles. The sum of all nameplates is therefore not automatically the capacity you need; dropping large loads without calculation is just as wrong. Load management limits peaks when it matches the appliance, meter and grid-operator procedure.

Record four data points per appliance: permitted supply voltage, need for a neutral, number of phases and maximum current per phase. Add inrush current, power factor and manufacturer conditions where they matter. “Three-phase” alone is not enough: a motor or charger for 3N~400 V may need a neutral or a different internal connection than a load for 3×230 V. Protection, cross-section, disconnection conditions and phase rotation are the electrician's call.

Upgrading or converting with the grid operator

Costs and lead times are set by the competent grid operator; there is no Belgian flat rate. They depend on the requested capacity, the street infrastructure, the meter position and the required changes to the internal installation. Prepare your request like this:

Have the EAN or connection reference, current rating and desired capacity ready.
Add appliance data and the planned commissioning date.
Ask explicitly about the available voltage, number of phases and neutral at the address.
Agree with the electrician what changes at the meter position, supply cable, main board, RCDs and phase distribution.

Only then can you compare the grid offer and internal works sensibly. After a significant change you update the single-line diagram and situation plan; whether a new inspection is required depends on the scope and nature of the change.

The supply in the single-line diagram

At the supply point, record voltage, type of current and connection configuration. Show the main protection and all active conductors unambiguously. On a 3×230 V network you do not draw a neutral; on 3N~400/230 V it appears where it is actually distributed. After a conversion you check board occupancy, protective devices, conductors and final circuits and bring the drawings up to the as-built state. Keep the previous version and create a new, dated one.

In PlanElec you document the street network (with or without neutral) and the building connection (single- or three-phase) as separate settings; the valid phase assignments for your circuits follow from them. The AREI/RGIE self-check warns about single-pole circuit breakers in homes (4.4.4.2), about phase imbalance above 30% as a practice recommendation and about implausible combinations of a 3×230 V connection with the stored earthing system. The grid operator confirms the available network and capacity; the inspection is carried out by the recognised inspection body.

Common decision errors

Reading only the meter: the display does not fully explain the network and conductor configuration.
Treating 3×230 V and 3N~400/230 V as equal: both are three-phase but give the appliance different voltages and conductors.
Treating kVA as kW: power factor and appliance determine the real power.
Taking charging power as connection capacity: the other simultaneous loads and load management are then missing.
Leaving the drawings after a conversion: supply, protection chain and phase assignment no longer match reality.
Opening sealed parts: you identify the connection from visible information, the grid operator or a professional.

Three typical starting points

Existing 1×230 V: first check the actual rating and whether a neutral is present. An EV charger with limited single-phase power and load management is often feasible; vehicle, charger, household load and grid operator decide. A high kW figure in a brochure proves no available capacity.

Existing 3×230 V: spread single-phase loads across the phase pairs and explicitly check each three-phase appliance for operation without a neutral. An appliance that internally needs 230 V to neutral does not fit just because its data sheet says “three-phase”.

Existing 3N~400/230 V: single-phase loads connect between line and neutral, three-phase appliances as specified by the manufacturer. A high calculated connection capacity does not lift the current limit per phase or the requirements for protection and cross-section.

Measurement and commissioning

You do not derive the final assignment from documents alone. A professional measures the actual voltage configuration, without opening grid-operator areas without authorisation, and checks phase rotation, neutral and protective conductor. After changes, the prescribed checks and measurements of the affected parts follow.

For controllable large loads, also watch their behaviour in operation. Load management must switch to a safe, documented state on loss of communication or incorrect readings. The configured limit matches the connection protection and accounts for peaks, not just averages. Changed settings are documented like any other design-relevant change.

Sources

Document the network and building connection separately in PlanElec →

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