Tutorial

Single-Line Diagram for a New Build: A Reliable AREI Checklist

From supply and protective devices to cable data, references and the matching position plan: a complete domestic new-build checklist under AREI Book 1 V06.

Published on 29 August 2026 11 min

Objective: document the installation that was actually built

For a new domestic electrical installation, the person responsible for the work prepares a single-line diagram and position plan. The single-line diagram is not an early design that can be left unchanged after construction. Before conformity inspection, it must match the installed boards, protective devices, wiring, circuits, loads and sources.

This checklist follows AREI/RGIE Book 1 V06 and focuses on the usual AC case. The provisions for earthed DC systems applicable from 1 April 2026 form a separate specialist area; AC conductor roles and symbols must not be improvised for DC.

1. Give the document set an identity

Record before drawing:

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

The single-line and position plans should carry the same version. A filename or export timestamp alone is lost when pages are printed or merged. A working draft must not contain a pre-emptive inspector endorsement or “AREI-compliant” statement. Endorsement belongs to the actual inspection procedure.

2. Establish the real supply

Start from connection data and construction, not a template:

single- or three-phase supply;
nominal voltage and AC/DC;
neutral and protective-conductor arrangement;
meter and service connection;
service protective rating and main isolating switch;
network and earthing arrangement needed for the protection design;
additional sources, inverters or transformers.

A Belgian 230 V socket does not identify whether the building has 3×400 V+N or 3×230 V. A false assumption affects pole count, neutral conductors, RCD wiring and loads. Connection agreement, board construction and measurements must agree.

3. Represent the full protective chain

Include main and sub-distribution boards with their supplies. Every final circuit should be traceable from the origin. Record as applicable:

main switch and upstream protective devices;
RCD waveform type, rated residual current, rated current and relevant timing characteristic;
fuses or circuit breakers with rating and required characteristic;
connections and downstream boards needed to explain the structure;
spare breakers as spares, without fictitious outgoing cable;
a unique label for every board and outgoing way.

Putting 300 mA upstream of 30 mA does not prove selectivity. Waveform type, enhanced immunity and time delay are different properties. Product coordination, short-circuit conditions and disconnection times remain design checks.

4. Give every final circuit a stable reference

Each elementary circuit receives a capital letter. Lighting points, sockets and control units are numbered from the upstream overcurrent device. Use the same identifier on the board label and position plan.

For every outgoing circuit, establish its purpose and loads, whether it is lighting, socket, mixed or dedicated, fixed appliances, intermediate boxes, assigned RCD and agreement across board and both diagrams. “Kitchen” is too vague where lighting, worktop sockets, dishwasher and cooking equipment use separate circuits.

5. Complete the wiring-system data

Subsection 3.1.2.2 requires type, cross-section, conductor count and installation method. Attach the information to the relevant segment. Wiring can change after a junction or connection box; one cable label at the circuit origin must not conceal a different downstream segment.

The design behind the diagram also checks load current, protective rating and permissible current capacity, installation and grouping, temperature, length and voltage drop, short-circuit and fault-loop conditions, minimum cross-sections and the protective conductor. Table 4.11 gives domestic copper ceilings, not a universal sizing calculation.

A neat XVB 3G2.5 label is only valuable if that cable is installed. Verify against visible construction and reliable as-built records.

6. Record outlets, boxes and controls

The single-line diagram includes sockets, lighting points, switches, connection/junction boxes and fixed equipment. Use Table 2.23. If no listed mark fits, define an unambiguous symbol in the legend.

Distinguish where relevant: single or multiple socket, protective contact, switched or data outlet; lighting point and switching function; push-button, relay, detector or home automation; fixed appliance or ordinary socket load; connection box or junction box. A general equipment box with a clear label is better than an unexplained decorative icon.

7. Include sources and specialist sections

PV, inverter, battery, generator or transformer belongs in the electrical structure. Source properties appear on the single-line diagram or remain available in the dossier. For domestic low-voltage PV, Section 9.1.2 additionally calls for operating and maintenance instructions, safety information and technical references for installed equipment.

A panel symbol beside the board does not document point of connection, protection and conversion equipment. Establish which source can energise what, where it connects and through which components. Do not guess whether a battery can export. Safety or critical installations may need additional lists and plans with their sources, circuits and loads clearly identified.

8. Synchronise the position plan

Place every represented board, box, socket, light, control, fixed machine and source on the position plan with the same reference. Check both directions:

find every single-line item on the floor plan;
find every floor-plan electrical symbol on the single-line;
compare circuit letter and number;
confirm floor, room and supplying board;
include concealed boxes and outdoor equipment.

Do not invent an unseen cable route. The position plan locates the required elements; additional cable or electrode plans should only contain reliable data.

9. Freeze the as-built state before inspection

The new installation undergoes conformity inspection before being put into use. The approved body compares construction with both diagrams and performs checks and measurements including earthing resistance, insulation, continuity and coordination of protective measures.

Immediately before the appointment compare site and dossier:

was a different breaker or RCD fitted?
did cable type or cross-section change?
was a socket, light or box added?
was a circuit moved to another RCD?
do board labels and references match?
are all pages from the same version?

Update the physical installation and records together. A technical defect must not be hidden by changing only the drawing.

10. Organise the dossier and later revisions

The domestic dossier contains the two diagrams, inspection reports and applicable evidence and alteration records. The owner keeps it in duplicate and passes it to a new owner.

After inspection, significant work calls for updated diagrams. Non-significant alterations follow their description rule and the position plan remains current. Retain the endorsed version separately from later revisions so the history is clear.

Final checklist

Reconcile design, site changes and commissioning

A new build almost always changes between tender and energisation. Keep an open deviation register containing the planned reference, the work actually carried out, the responsible decision, affected drawings and any evidence still missing. Typical entries include a relocated board, an extra outdoor socket, revised heat-pump input data or a PV inverter added late. The design diagram becomes an as-built diagram only after every item has been resolved or explicitly marked as not installed.

Then walk through the installation with the labels and commissioning records. Do not operate circuits on the basis of assumed room names alone. Compare each physical board label with the diagram reference and the point on the position plan. If conductors, protective devices or settings change during commissioning, update the records afterwards. An early PDF export is not a reliable final edition merely because it looks complete.

Worked review of one new final circuit

For a fixed tumble dryer, “utility room” is not enough. The records should show the supplying board and protective chain, the stable circuit reference, the wiring system with conductor count and cross-section, and the fixed equipment at the end. The same reference appears at the actual connection point on the position plan. Keep the manufacturer's instructions, rating data and required settings separately as technical documentation.

Review the interfaces next. Is the protective-conductor path traceable? Does the real connection method match the drawing? Did a dedicated route in the design become a shared run on site? Is there a junction box missing from the diagram? These checks prevent formally complete pages from preserving an obsolete design state.

Hand over a controlled document set

Identify the final issue clearly with project, address, revision and export date. Assemble the single-line diagram, position plan, inspection report and relevant technical documents in an ordered dossier. Keep working copies and superseded revisions separate and visibly historic. The owner should know which files are current and that later alterations require another documentation update.

The official FPS Economy page on domestic electrical inspections lists the minimum diagrams to provide and summarises their content. It does not replace the detailed requirements of AREI/RGIE Book 1 V06 or competent assessment of the particular project.

Preparing with PlanElec

PlanElec can keep the floor plan, electrical topology and board data in one project, export both diagrams as PDF and run an indicative self-check for supported rules. It does not replace supply verification, cable design, site survey or measurement. A software check with no findings is not an AREI conformity statement; the approved body performs the official inspection.

Start a new-build project in PlanElec →

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

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