The single-line diagram: what the RGIE really requires

The single-line diagram is part, together with the position plan, of the file of every domestic electrical installation. For a new installation, a significant modification or a significant extension, Book 1 of the RGIE (section 3.1.2) makes the person responsible for carrying out the works draw it up, and sets out what it must contain at a minimum. Here are those requirements, as the text states them, and a method for producing a diagram that matches the installation.

What the single-line diagram is for

Chapter 2.12 of Book 1 defines the circuit diagram as a single-line or multi-line diagram that represents the elementary circuits, their interconnections and the electrical equipment, and gives the make-up and characteristics of the installation. On the single-line diagram, each circuit is drawn as a single line, without following the actual route of the cables through the building.

It goes hand in hand with the position plan, which shows where the various parts of the installation are located. The two documents share the same referencing, and the report of the compliance inspection of a domestic installation certifies, among other things, that the installation has been carried out in accordance with the single-line diagrams and position plans (subsection 6.4.6.4).

What the diagram must contain

For a domestic installation, subsection 3.1.2.2 provides that the single-line diagram shows at least:

• The wiring systems: type, cross-section and number of conductors, and the installation method.
• The residual current devices (RCDs): their type and characteristics.
• The overcurrent protective devices: their type and characteristics.
• The connected equipment: switches, connection boxes, junction boxes, socket-outlets, lighting points, fixed machines and appliances.
• The sources: for example transformer, solar panel, inverter, battery.

Subsection 3.1.2.1 adds the voltage and the nature of the current, the name, capacity and VAT number (where applicable) of the person responsible for carrying out the works, and the address of the installation. It also provides that any old part of the installation whose construction on site began before 1 October 1981 and which appears on the single-line diagrams is marked there with the words « partie ancienne » (old part). Section 3.1.2 also requires diagrams to state unambiguously their number, their version and the date of that version. If the installation is found compliant at inspection, the person responsible for the works and the accredited body sign and date the single-line diagrams and position plans.

The diagram also shows which circuits sit behind which RCD. For domestic installations, subsection 4.2.4.3 requires at least one RCD of at most 300 mA at the origin of the installation and, immediately downstream, at least one high or very high sensitivity RCD to which at least the following are connected: socket-outlets not intended for fixed appliances, lighting, locations containing a bath or shower, and washing machines, tumble dryers and dishwashers, with at most 8 final circuits per device. If the dispersion resistance of the earth electrode exceeds 30 ohms, there are at least two of these high or very high sensitivity RCDs, and each takes at most sixteen single or multiple socket-outlets, a fixed appliance or a set of fixed appliances controlled by a common switching device being treated as equivalent to a socket-outlet.

Referencing circuits and points

Book 1 lays down precise referencing (subsection 3.1.2.1):

• Each elementary circuit is identified by a capital letter.
• Each lighting point, socket-outlet and control unit receives a number giving the order in which it is met along the circuit, starting from the upstream overcurrent protective device.
• On the position plan, each lighting point, socket-outlet and control unit carries the letter of its circuit and its order number from the diagram; each switch carries the letter of its circuit and the number of the point it controls.

The symbols to use are those of table 2.23 (chapter 2.13), a non-exhaustive list: where no symbol is listed in that table, any other clearly identifiable symbol defined in the legend of the single-line diagrams and position plans may be used (subsection 3.1.2.1). In the distribution board, subsection 3.1.3.1 requires the control, protective and isolating devices of circuits to be marked clearly, visibly and indelibly, unless any possibility of confusion is ruled out.

The inconsistencies to avoid

An incomplete or outdated diagram does not allow the installation to be checked. Watch for:

• A diagram that no longer matches the installation. A circuit added during the job, a circuit breaker swapped: diagrams, plans and documents are kept up to date and available on site to anyone authorised to supervise, inspect, maintain, repair or alter the installation (subsection 3.1.2.1).
• Referencing that does not line up. Circuit C on the diagram carries a different letter on the position plan, or does not appear there at all.
• Mismatched cross-sections and ratings. The compliance inspection report certifies that the overcurrent protective devices are suited to the cross-sections of the circuits they protect (subsection 6.4.6.4): the diagram must make that readable.
• Forgotten equipment. The charging point, the water heater in the attic, the feed to the garden shed: fixed machines and appliances are part of the minimum content of the diagram.
• An incomplete file. The file of a domestic installation contains the single-line diagram or diagrams and the position plan or plans (section 9.1.2): one does not replace the other.

For the place of the diagrams and plans in the inspection by the accredited body, see our article on how the RGIE inspection unfolds.

The method for a clean diagram

Four steps, in this order:

• 1. Take stock board by board. Record, board by board, what is really in it: RCDs, circuit breakers, ratings. No guessing, no working from memory.
• 2. Trace circuit by circuit. For each protective device, follow the circuit to its points of use, note the cross-section, cable type and installation method, then assign the circuit letter and the order numbers.
• 3. Cross-check with the position plan. Each distribution board, connection or junction box, socket-outlet, lighting point, switch, fixed machine or appliance and source shown on the diagram appears on the plan (subsection 3.1.2.3), in the right room; the numbered points carry the same letter and number.
• 4. Have it checked. A read-through by a colleague, or by a tool that checks each circuit against the rules of Book 1.

That is the work Amperio helps with: you survey the installation room by room, by hand or by voice, the diagram and the plan are built together with the same referencing, and each circuit is checked against the RGIE (Book 1) as you go. For the comparison with traditional drawing tools, the full comparison is here.

And if the original diagram has vanished?

When a house is sold or a job is taken over, the installation sometimes exists without a file. Survey the installation, then redraw both documents. For the inspection visit at the sale of a dwelling with an old domestic installation, whose execution began before 1 October 1981, section 8.4.2 provides that, where no diagrams and plans are available, the accredited body’s representative draws up a summary description of the boards and a freehand sketch. These documents cannot be used as a single-line diagram or position plan, and the absence of the regulatory documents is recorded as an infringement. For the existing parts of an old domestic installation, section 8.2.1 (point 7) allows a simplified diagram and plan; how this applies to a specific installation is for the accredited body to decide. Our guide on the electrical file when selling a house covers this case.

This article is informative. It replaces neither the RGIE (Book 1) nor the advice of your inspection body.