Single-Line Diagram for a New Build: The AREI Checklist up to Inspection

What must a new-build single-line diagram contain?

A single-line diagram for a Belgian new build shows the installation as actually built: a title block with number, version, date, address and responsible person, the voltage and type of current, every distribution board, all residual current and overcurrent devices with their characteristics, cable type, cross-section, number of conductors and installation method, switches, boxes, socket outlets, lighting points, fixed appliances and sources. The situation plan shows the same elements with the same reference at their location. The basis is AREI/RGIE Book 1 version 06, applicable since 1 April 2026, above all Section 3.1.2.

The single-line diagram and the situation plan are drawn up by the person responsible for carrying out the work (Subsection 3.1.2.1 a). Before the conformity inspection they match the installed state, not the first design. This checklist takes you there in ten steps. It covers the usual AC case; earthed DC systems, which version 06 now regulates, are a separate field where you do not simply carry over AC conductor roles and symbols.

Mandatory content at a glance

1. Set the title block and responsibility

Give the document set a clear identity before you draw the first circuit:

• document number, version and the date of that version;
• address of the installation;
• name and capacity of the person responsible for the work, VAT number where applicable;
• fields for dates and signatures;
• voltage and type of current on the single-line diagram.

The single-line diagram and the situation plan carry the same version. A file name is not enough, because printouts and merged PDFs lose it. Nor is the export date the date on which the installation was surveyed.

The signature and visa of the approved body are only added during inspection, once the installation is found compliant (Subsection 3.1.2.1 a). A working version therefore carries no anticipated approval and no “AREI-compliant” statement.

2. Establish the supply

The diagram starts from the real supply, not from a template. Record:

• single-phase or three-phase supply;
• nominal voltage and type of current;
• neutral and protective conductor;
• connection and meter arrangement;
• rating of the supply protection and the main switch-disconnector;
• earthing system and earthing concept, as far as design and protection need them;
• additional sources such as a PV inverter or transformer.

No socket outlet tells you whether a supply is a 3×400 V network with neutral or a 3×230 V network. A wrong assumption carries through to the number of poles, the neutral, the wiring of the RCDs and the loads. Compare the connection contract, the board layout and a measurement; when in doubt, the grid operator confirms the supply data.

3. Capture every board as part of the protection chain

Record the main board and sub-boards with their feeds and interconnections. The path from the origin to every final circuit is fully traceable. Depending on the installation, this includes:

• main switch and upstream protection;
• RCDs with type, rated residual current, rated current and relevant characteristic;
• fuses or circuit breakers with rating and curve;
• busbars, links and sub-boards that explain the structure;
• spare breakers shown as spares, without an invented cable or load;
• a unique name for every board and outgoing way.

A 300 mA device followed by a 30 mA device does not prove selectivity on its own. Waveform type, increased immunity and time delay are separate properties. Short-circuit conditions, disconnection times and coordination according to the manufacturer belong to the technical design.

4. Give every final circuit a stable reference

Each elementary circuit gets a capital letter. You number lighting points, socket outlets and control devices in the order in which they occur in the circuit, starting from the upstream overcurrent device (Subsection 3.1.2.1 a). The same reference appears on the board label.

For every outgoing way the survey answers:

• Which use and which loads belong to it?
• Is it a lighting, socket, mixed or dedicated appliance circuit?
• Which fixed appliances are connected?
• Are there junction or branch boxes?
• Which RCD protects the circuit?
• Do the diagram, board label and situation plan agree?

“Kitchen” is not a usable name when lighting, worktop sockets, dishwasher and hob each have their own circuit. Names help orientation; only the electrical reference is unambiguous.

5. State all cable data

Subsection 3.1.2.2 a requires type, cross-section, number of conductors and installation method. Record them per cable section. After a branch or junction box, the cable or installation method can change; a single cable label at the start of the circuit hides that.

The design behind the diagram goes further. Check separately:

• design current, protective-device rating and current-carrying capacity;
• installation method, grouping, ambient temperature and thermal insulation;
• cable length and voltage drop;
• short-circuit and fault-loop conditions;
• minimum cross-sections and specific circuit rules;
• the stated protective conductor against the cable actually installed.

Table 4.11 gives, for domestic installations, the highest fuse or circuit-breaker rating per cross-section, for example a 20 A circuit breaker for 2.5 mm². It is a ceiling, not a complete cable calculation. A neat label such as XVB 3G2,5 is worthless if a different cable was installed on site.

6. Record loads, boxes and controls

The single-line diagram contains switches, junction and branch boxes, socket outlets, lighting points and fixed machines and appliances (Subsection 3.1.2.2 a). Use the symbols from Table 2.23. Where a sign is missing, define an unambiguous symbol in the legend.

Make visible what matters technically:

• single or multiple socket outlet;
• socket with earth contact, switched or special socket;
• lighting point and actual switching function;
• push button, relay, motion detector or home-automation control;
• permanently connected appliance or ordinary socket load;
• junction box or branch box.

A generic appliance symbol with clear text is better than an invented pictogram. Function, reference and connection are what count.

7. Draw sources and special parts

PV installation, inverter, battery, generator and transformer belong in the electrical structure of the single-line diagram; the situation plan shows where they are. For a domestic low-voltage PV installation, the installation file additionally contains operating and maintenance instructions, safety instructions and the technical references and characteristics of the installed equipment such as make, model and power (Section 9.1.2).

A PV arrow next to the main board describes neither the connection point nor the protection chain. Draw which source can feed in, where it connects and which components lie in between. Whether a battery can export to the grid is something you take from the manufacturer documentation rather than guess.

Where safety or critical installations exist, a list and a plan of those installations are added; their sources, circuits and loads are clearly identified on the single-line diagram (Subsection 3.1.2.1 a).

8. Keep the situation plan in sync

Every board, box, socket outlet, luminaire, control, fixed appliance and source on the single-line diagram appears at its location on the situation plan (Subsection 3.1.2.3 a). The reference C3 means the same element in both documents. Switches carry the letter of their circuit and the number of the point they control.

Check in both directions:

1. find every diagram element on the situation plan;
2. find every plan symbol on the single-line diagram;
3. compare letter and number;
4. confirm floor, room and board assignment;
5. include concealed boxes and outdoor elements.

You do not draw unknown cable routes. The situation plan locates the required components; additional cable or earthing plans are only produced from reliable data.

9. Freeze the installed state before the conformity inspection

Before it is put into use, the new installation undergoes the conformity inspection (Chapter 6.4). The approved body measures the earth resistance and the insulation level and certifies in its report that the RCDs match the earth resistance, that the overcurrent devices match the circuit sections they protect and that the installation was built according to the single-line diagram and situation plan. It also checks the continuity of bonding and protective conductors (Subsection 6.4.6.4).

Shortly before the appointment, look for real deviations, not typos:

• Was a different circuit breaker or RCD installed?
• Did a cable cross-section or type change?
• Was a socket outlet, luminaire or box added?
• Was a circuit moved to a different RCD?
• Do board labels and references match?
• Do all pages belong to the same version?

Correct the installation and the documents together. A technical fault gets fixed, not airbrushed out of the drawing.

10. Organise the file and future changes

The file of a domestic installation contains the single-line diagram, the situation plan, the conformity inspection reports, any evidence about the equipment and, later, the documents for alterations. The owner keeps the file in two copies and hands it over to a new owner (Section 9.1.2).

After the inspection you keep the diagram up to date. Substantial alterations or extensions require updated diagrams and plans; for a non-substantial one, a short dated and signed description is enough, and the situation plan always shows the current state (Subsection 3.1.2.1 a). Keep the inspected version and every later version traceable.

Final check

• document number, version, date, address and responsible person complete
• voltage, type of current and real supply configuration stated
• all boards and sources included
• residual current and overcurrent protection with characteristics recorded
• every final circuit uniquely referenced
• cable type, cross-section, number of conductors and installation method complete
• socket outlets, lighting points, boxes, switches and fixed appliances present
• symbols from Table 2.23 or unambiguously defined in the legend
• references match the board and the situation plan
• site changes reflected in both documents
• additional documents for PV, safety or special installations added
• design calculations and measurements completed outside the diagram

Align design, site and commissioning

A new build almost always changes between tender and commissioning. Keep an open deviation list: planned reference, executed change, who decided, affected plans and missing evidence. Typical cases are a relocated board, an extra outdoor socket, a different heat pump rating or a PV inverter added late. Only when every line is closed or explicitly marked as not executed does the design diagram become an as-built diagram.

Then walk through the installation with labels and measurement records. Do not switch circuits based on assumed room names. Compare the marking in the board with the reference on the diagram and the point on the situation plan. If conductors, protective devices or settings change during commissioning, the documentation follows; an early PDF export is not a final version.

Example: a new final circuit for the tumble dryer

For a permanently connected tumble dryer, “utility room” is not enough. The file shows which board and which protective devices the circuit comes from, which reference it carries, which cable with how many conductors and which cross-section is installed and which appliance sits at the end. Washing machine, tumble dryer and dishwasher each get a dedicated circuit (Subsection 5.2.1.2) and are protected by an RCD of high or very high sensitivity (Subsection 4.2.4.3 b). The same reference appears at the real connection point on the situation plan. Appliance manual, ratings and settings are kept as technical documentation.

Then check the interfaces: is the protective-conductor path traceable? Does the connection method match the drawing? Did a dedicated supply become a shared run on site? Is a branch box missing from the diagram? These questions stop formally complete pages from preserving an outdated design state.

Hand over a controlled document set

Identify the final issue clearly with project, address, revision and export date. File the single-line diagram, situation plan, inspection report and technical documents in an ordered dossier. Mark working copies and superseded revisions separately as history. The owner then knows which files are current and that later changes have to be documented again.

The official FPS Economy page on domestic electrical inspections lists the minimum plans to present and summarises their content. The detailed requirements are in AREI/RGIE Book 1, version 06.

Preparing with PlanElec

PlanElec keeps the floor plan, electrical topology and board data in one project. The single-line diagram and situation plan come from the same model, carry the same references and leave as PDFs or as a compiled installation dossier with cover sheet and document index. The AREI/RGIE self-check tests the supported rules against your project data and shows open points before the inspector finds them.

The roles are clearly split: PlanElec structures and checks the documentation. Supply verification, cable design, site survey and measurements remain the work of the professionals on site, and the approved body carries out the official conformity inspection.

Related guidance

• Coordinate the single-line and situation plans
• Understand AREI electrical symbols
• Prepare for electrical inspection
• Is a main switch mandatory under AREI?
• Drawing up a bill of materials for an electrical installation
• Smoke detectors in Belgium: the rules per region

Start a new-build project in PlanElec →

Basis: AREI/RGIE Book 1 V06, particularly Chapter 2.13, Section 3.1.2, Table 4.11, Subsection 4.2.4.3, Subsection 5.2.1.2, Chapter 6.4 and Section 9.1.2. The official text and the installed system remain decisive.