Single-Line Diagram vs. Position Plan: Difference and Coordination
A single-line diagram shows electrical structure; a position plan locates equipment. Shared circuit references make the two Belgian domestic records work together.
The difference in one sentence
The single-line diagram shows how the supply, protective devices, wiring systems and loads connect electrically. The position plan, also called a situation plan in English product language, shows where the relevant equipment is located in the building. Shared circuit identifiers connect the electrical path to the real room.
Both documents are required for a new domestic installation and for significant alterations or extensions. They are not interchangeable views. A floor plan does not specify RCDs, breakers or conductor data; an electrical tree does not locate the socket beside a particular door.
A shared identity and version
Book 1 V06 subsection 3.1.2.1 requires an unambiguous number, version and version date for plans and records. Domestic diagrams also state the name and capacity of the person responsible for the work, their VAT number where applicable and the installation address. Voltage and current type appear on the single-line diagram.
Where the approved body establishes conformity, the drawings are dated and signed or endorsed and join the inspection report in the installation dossier. A PDF exported before inspection is therefore not already an approved drawing or a positive report.
What the single-line diagram contains
Subsection 3.1.2.2 lists at least:
- wiring-system type, cross-section and conductor count;
- wiring installation method;
- type and characteristics of residual-current devices;
- type and characteristics of overcurrent devices;
- switches, connection boxes and junction boxes;
- socket outlets and lighting points;
- fixed machines and appliances;
- sources such as transformers, photovoltaic cells, inverters and batteries.
It answers structural questions: which RCD is upstream of circuit C, which breaker protects a cable, how does a junction branch, and which loads follow? It does not give a scaled location in the home.
Each elementary circuit receives a capital letter. Lighting points, sockets and control units are numbered in order from the upstream overcurrent device. That sequence is an electrical reference, not necessarily the walking route through the rooms.
What the position plan contains
Subsection 3.1.2.3 requires the physical location of items represented on the single-line diagram, including:
- distribution and switchgear assemblies;
- connection and junction boxes;
- sockets, lighting points and switches;
- fixed machines and appliances;
- sources, inverters and batteries.
A legible floor plan distinguishes storeys and rooms. Scale can help, but the position must above all be unambiguous. Placing a socket in the centre of a bedroom does not identify the wall on which it is installed. Concealed junction boxes matter because maintenance must be able to find them later.
The position plan is not automatically a complete cable-route plan. The rule calls for the listed equipment locations. Unknown concealed routes should not be invented; underground cables and specialist systems may require additional plans.
The shared reference is the bridge
Suppose circuit B supplies three socket outlets and one lighting point. The single-line diagram identifies them B1 to B4 in electrical sequence. The position plan places each reference at its real location. A switch controlling B4 is marked so that the controlled point is clear.
An inspector or electrician can then move from the protective device to the load, and from the room back to the board. If B3 is absent from the floor plan, its location is unknown. If the plan shows a further socket B5 that does not exist on the single-line diagram, the two documents describe different installation states.
Build both from one survey
A robust workflow is to:
- record storeys, rooms, boards and sources;
- establish the protective chain and final circuits;
- assign every socket, appliance and box to the correct circuit;
- create each reference once and reuse it in both views;
- add cable and equipment properties to the electrical path;
- verify physical positions on site;
- export both documents with the same version and status date.
Board labels are clues, not proof. Existing circuits may need safe identification by a competent person. A guessed concealed connection is not made reliable by drawing it neatly.
Alterations and document history
For a non-significant alteration, a short dated and signed description may replace a completely new single-line diagram where the AREI conditions are met. Every domestic alteration or extension is nevertheless added to the position plan so it continuously represents the existing state. Significant work requires the corresponding updated diagrams.
Older sections whose on-site execution began before 1 October 1981 and which appear on the single-line diagram are marked “old section”. The label is not blanket approval; the actual legacy deviations must still be assessed.
Version the documents as a pair. A position plan at Version 4 beside a single-line diagram at Version 2 makes the inspected state unclear. Retain earlier endorsed versions in the dossier rather than erasing the history.
Typical inconsistencies
| Difference | Why it matters |
|---|---|
Single-line has C1–C6, position plan only C1–C5 | one item cannot be located or is not electrically recorded |
| Different circuit letter at the same socket | its location cannot be tied to the protective device |
| Inverter appears only on the floor plan | its source connection and protection are absent |
| Junction box appears only on the single-line | maintenance cannot find it physically |
| Different address or version | the files may concern different states or installations |
How the approved body uses both
During conformity inspection, the approved body checks among other things whether the installation was built according to the single-line diagram and position plan. The single-line makes protection and wiring assignments traceable; the position plan lets the inspector find the identified points. Measurements and visual inspection remain separate parts of the process.
A mutually consistent pair can still contain a design error. Conversely, technically sound work is poorly documented when the diagrams contradict each other. Keep three decisions separate: the records are complete, the design has been competently checked and the installed system has passed official inspection. None follows automatically from a polished PDF.
After a conforming result, the owner receives the endorsed drawings and report for the dossier. The approved body retains a copy for the prescribed period, but the owner remains responsible for keeping their own records current and available for later work.
Treat the approved body's copy as a recovery option, not version control. A later alteration kept only in a loose note makes the set inconsistent again. Attach each change to the correct versions of both diagrams.
A practical reconciliation before release
Do not reconcile the files only by looking at the pages side by side. Work circuit by circuit. Start from a list of circuit letters, then follow each circuit from its protective device to the final item and ask the same questions in both records: which points exist, what reference identifies them, where are they located, and what fixed function do they perform? Record a mismatch as an open task instead of hiding it under a broad room label.
For circuit H, the list might contain ceiling light H1, wall light H2 and their associated switches. The single-line diagram shows how these points sit electrically behind protection and wiring. The position plan shows H1 in the hall and H2 outdoors. If H2 is missing from one page, the other page is not automatically correct. Resolve the difference against the survey and installed system, then correct both records.
Also perform cross-circuit checks:
- Every board and fixed energy source on the single-line has a findable location.
- Relevant connection and junction boxes use consistent identifiers.
- Fixed machines are not represented only by room text.
- Continuation references between sheets terminate at the intended circuit rather than a similarly named group.
- Header, address, page numbering, date and revision make one identifiable document set.
Example: recording a small extension
When an extra socket is installed in a study, first establish the circuit to which it was actually connected. If it is the next point on circuit D, it may receive D6; add that code at the electrical position on the single-line and at the physical position on the position plan. Do not infer its wiring and protection from the nearest socket on the drawing. Verify the real connection and advance the date and revision of both documents together.
For a non-important alteration, the AREI may permit a short description instead of a new single-line diagram, while the position plan still has to reflect alterations and the current installed position of elements. Whether particular work is important or non-important requires competent assessment. Do not use the provision to accumulate years of undocumented small works. Once assignment or current state is no longer clear, consolidate the records.
The official FPS Economy page on domestic electrical inspections summarises the contents and relationship of the two documents. The current official Book 1 remains decisive; published examples are guidance, not drawings to copy without surveying the installation.
PlanElec's role
PlanElec combines floor-plan positions and electrical topology in one project. The single-line diagram and position plan can be exported as PDF, and an indicative self-check evaluates supported rules that are decidable from the recorded data. Shared data reduces duplicate entry but does not guarantee that the survey was correct.
PlanElec cannot see concealed cables, perform measurements or endorse drawings. Actual circuit assignments, equipment properties and wiring data require competent verification. Only an approved body performs the official inspection.
Related guidance
- AREI symbols for both diagrams
- New-build single-line diagram checklist
- Draw a position plan step by step
Open PlanElec to prepare and export both diagrams →
Basis: AREI/RGIE Book 1 V06, Section 3.1.2 and Section 9.1.2. The official text, installed state and approved inspection remain decisive.