Single-Line Diagram Software: Build One Online in 15 Minutes

What a single-line diagram has to contain

An SLD is a schematic, not a layout. Components are shown by symbol and connection, not by physical position. A useful diagram carries:

• Supply and source. Transformer, meter, main switch or breaker, and the point of supply with its rating.
• Distribution path. Main board and any sub-boards, with the feeder cable type, size and length.
• Protective devices. Breaker type and rating per outgoing way, RCD/RCBO where required, and the breaking capacity.
• Circuits. A unique designation per way, the load it serves, and the connected load in kW or VA.
• Conductor data. Cross-section, cores and material per circuit, with the installation method that justifies the current-carrying capacity.
• Earthing and bonding. Earth bar, main protective conductor, equipotential bonding, and any earth electrode.
• Notes and basis of design. Standard and edition, ambient conditions, discrimination assumptions, and revisions.

If a reviewer cannot check protection, cable size and load from your diagram without opening another document, the diagram is incomplete. That is the practical test, and it is also the reason a schedule and an SLD have to be generated from the same data rather than drawn twice.

IEC and NEC: where the diagrams diverge

The drawing grammar is similar; the data on it is not. This matters when a tool is built for one market and sold in another.

Two consequences for software choice. First, a tool that only speaks one code will produce diagrams that a reviewer in the other market rejects on detail, even if the topology is right. Second, any calculation must state its basis: which edition, which installation method, which ambient temperature. A diagram without that note is an opinion, not a design.

The 15-minute workflow

The sequence below is what a browser tool makes fast. Times are for a typical flat or small office with six to twelve circuits.

Minute 0–3: import the plan. Upload a PDF or image from a survey, or draw the outline. Trace exterior and interior walls, close the rooms, and mark wet areas. Everything downstream depends on rooms being closed shapes: circuits are assigned per room, and the panel schedule groups by area.

Minute 3–6: place devices. Drop sockets, luminaires, switches and fixed appliances. Group them into circuits as you go rather than afterwards. A sensible default is one circuit per room for sockets, separate circuits for kitchen appliances, and lighting split by floor or by area.

Minute 6–9: build the panel. Choose the board, set the supply (single-phase or three-phase), add the main breaker and the outgoing ways. Each circuit you created appears as a way; assign breaker curve, rating and residual-current protection. This is where most errors are caught, because an oversized breaker next to a 1.5 mm² cable is visible immediately.

Minute 9–12: let the numbers run. Load per phase, total connected load with demand factors, design current, voltage drop and cable size. The tool recalculates as you change a rating. Read the results rather than accepting them: a green check means the rule passed, not that the design intent is right.

Minute 12–14: generate the diagram. The single-line diagram is derived from the panel data, so it matches the schedule by construction. Arrange the layout for legibility: supply at the top, board in the middle, ways in a readable order, notes at the bottom.

Minute 14–15: check and export. Run the design checks, fix what they flag, then export. A PDF is the handover format; DXF is for whoever still edits in CAD; XLSX for the bill of materials.

If you want to see the sequence rather than read it, open the demo project — it loads with an example plan and panel so you can click through the steps.

Common SLD mistakes

Most rejected diagrams fail on the same handful of points.

The first row is the expensive one. When the diagram is drawn by hand next to a spreadsheet schedule, the two drift apart after the second revision, and nobody notices until the electrician is on site.

Export and handover

What the recipient needs depends on their role:

• Client or approval body: PDF, readable at A3, with the standard and edition named.
• Contractor: PDF plus a schedule listing cable types and lengths; DXF if they redraw.
• Procurement: a spreadsheet of devices and materials that matches the diagram.
• BIM coordination: IFC where the model matters, not for the diagram itself.

Check the exported PDF on a machine without the software before you send it. Fonts, line weights and symbol sizes are the usual casualties, and they are embarrassing in a submission.

When a browser tool is not enough

Be clear about the boundary:

• Plant and industrial distribution with short-circuit studies, discrimination and arc-flash analysis needs a dedicated package, not a drawing tool.
• Very large multi-board installations become slow to manage in a browser editor; desktop CAD still handles big drawings more comfortably.
• Offline work is not possible with GorkyCAD; the editor needs a connection.
• DWG round-trips are limited: DXF import and export work, but attributes and dynamic blocks do not survive.
• Control and PLC schematics are outside the product's scope.
• The 41 checks are not a certification. They catch common errors; a qualified engineer still signs the design, and local requirements may differ from the rule set.

For a flat, a house, a shop or a small office, none of that usually blocks the work. For a factory substation, it does.

Making the diagram part of the project, not an afterthought

The reason diagrams get reworked is that they are produced at the end, from memory, after the plan has changed three times. The alternative is to keep one data set: rooms, devices, circuits, panel, diagram, schedule, bill of materials. Change a circuit and everything downstream follows. That is the whole argument for a connected tool over a drawing program, and it is also the reason the export step takes a minute instead of an afternoon.

Start with the demo, check the pricing when you know which plan fits, and read the documentation for the calculation basis and export formats. For the broader category, see the electrical CAD buyer's guide; for panel documentation specifically, EPLAN alternatives covers the heavier end of the market.

Sources

• IEC — standards catalogue (IEC 60364 series, IEC 60617 symbols): iec.ch
• NFPA 70, National Electrical Code: nfpa.org
• Autodesk — AutoCAD Electrical toolset: autodesk.com
• EPLAN — Electric P8: eplan.com
• QElectroTech — open-source schematic editor: qelectrotech.org

Informational only, not legal or engineering advice. Confirm requirements against the edition of the code in force for your project, and have designs reviewed by a qualified engineer.