ElecAS
EleCAD: Free Online Single Line Diagram Builder
EleCAD is a free, browser-based single line diagram (SLD) builder for Australian electrical designers, engineers, electricians, contractors and project teams. Draw and edit electrical single line diagrams online with no install, no licence file and no plug-ins: just open the browser and start placing switchboards, busbars, loads, inverters, protective devices and cables. What separates EleCAD from a drawing tool is that the diagram is a calculation model, not lines on a page: every cable carries conductor material, insulation, cores, installation method, length and derating; every switchboard tracks its busbar sections, incomer and outgoing ways; every protective device carries a real catalogue record with its trip settings; and every load contributes to the upstream maximum demand. From that model EleCAD runs a live design check on every circuit as you draw: AS/NZS 3008.1.1 current-carrying capacity after derating, per-segment and cumulative voltage drop against your limit with a reserve held back for final subcircuits, voltage rise from PV and battery inverters to AS/NZS 4777.1 with an optional site export limit, prospective short-circuit current (maximum and minimum) at every node, earth fault loop impedance built from the full R + jX loop including the earth conductor, the adiabatic I²t ≤ k²S² short-circuit withstand check on both the active and the earth conductor, device breaking capacity against the fault level where it is installed, discrimination between upstream and downstream devices, and maximum demand against the supply capacity. Cables can run as multiple parallel sets, with impedance, voltage drop and loop impedance divided across the runs, and earth conductors sized automatically or manually with their own parallel runs. Switchboards support multiple busbar sections with sub-bus groups, per-section protection, RCDs, incomers and spare poles. Every fault is listed with the fix that resolves it, and auto design sizes the cable and selects the protective device together until the two agree. Export a branded PDF carrying the diagram, title block, legend, compliance summary and the cable, voltage drop, voltage rise, load, circuit breaker and switch schedules, or a DXF that opens in AutoCAD, Revit and BricsCAD as fully editable geometry. EleCAD pairs natively with the ElecAS calculator suite (cable size, voltage drop, maximum demand Tables C1/C2/C3, conduit sizing, generator and UPS battery sizing), so the diagram and the calculations stay in lock-step. A practical alternative to AutoCAD Electrical, ETAP, EasyPower and SmartDraw for Australian design, concept SLDs, tender drawings and project documentation.
EleCAD single line diagram software: key facts
- EleCAD is a free, browser-based single line diagram builder with no install and no licence file.
- The diagram is a calculation model: EleCAD sizes every cable to AS/NZS 3008.1.1 using the same selection engine as the ElecAS Cable Size Calculator.
- Eight compliance checks run live on every circuit as you draw: current-carrying capacity after derating, voltage drop, voltage rise to AS/NZS 4777.1, prospective fault current, earth fault loop impedance, adiabatic short-circuit withstand on the active and earth conductors, device breaking capacity, and discrimination.
- Circuits can run as multiple parallel cable sets, with impedance, voltage drop and earth loop impedance divided across the runs.
- Switchboards support multiple busbar sections with sub-bus groups, per-section protection and RCDs, and dedicated essential-services sections.
- Every fault is listed with the fix that resolves it, and auto design sizes the cable and picks the protective device together until the two agree.
- Diagrams export to a branded PDF with cable, voltage drop, voltage rise, load, circuit breaker and switch schedules, and to editable DXF for AutoCAD, Revit and BricsCAD.
- Drawing and editing needs no account; downloading the PDF or DXF requires a free ElecAS account and the download itself stays free.
- EleCAD is a desktop and laptop tool: the canvas needs a browser window at least 1024 pixels wide.
Who EleCAD single line diagram software is for
Australian electrical engineers, designers, electricians, contractors, estimators, building services consultants and project managers building or reviewing single line diagrams, switchboard concepts and early-stage electrical documentation.
Australian standards EleCAD works to
- AS/NZS 3000:2018 (Wiring Rules)
- AS/NZS 3008.1.1:2025 (cable selection, derating and impedance data)
- AS/NZS 4777.1 (grid connection of inverters: voltage rise)
- AS/NZS 3013 (essential services / fire-rated wiring systems)
- Australian electrical drawing conventions
What EleCAD does: single line diagram and calculation features
- Free, online, browser-based: no install, no licence file, no plug-ins. Open any modern desktop browser and start drawing.
- Drag-and-drop palette for switchboards, busbars, loads, PV / battery inverters, spare poles and a repeatable multi-unit bundle, plus inline isolators, circuit breakers, RCDs, fuses, MEN links, surge diverters and direct or CT metering.
- Cable sizing to AS/NZS 3008.1.1 on every run: copper, flexible copper or aluminium; V-75, X-90, R-90, X-110 and R-110 insulation; single or multi-core; full derating for ambient and soil temperature, soil thermal resistivity, depth of burial and grouping.
- Multiple cable sets: run any circuit as parallel cables, with impedance, voltage drop and earth loop impedance divided across the runs, and a separate parallel-run count for the earth conductor.
- Voltage drop checked per segment and cumulatively from the point of supply against your site limit, with a reserve held back for final subcircuits, and each board reporting the worst voltage drop anywhere downstream of it.
- Voltage rise to AS/NZS 4777.1: PV and battery inverters push current back up the mains, and the cumulative rise from the point of supply is checked against your limit, with an optional site export limit that caps it.
- Short circuit study: prospective three-phase fault current, maximum and minimum, computed at every node from the source impedance plus the accumulated cable impedance, with manual overrides for source Ze and Isc.
- Earth fault loop impedance from the full R + jX loop, including the earth conductor and its own parallel runs, checked against the trip current of the actual protective device fitted.
- Adiabatic I²t ≤ k²S² short-circuit withstand check on both the active and the earth conductor, plus a breaking-capacity check against the fault level where each device is installed.
- Multiple busbar sections per switchboard, with sub-bus groups for tied and jointed buses, per-section protection, RCDs, connectors, spare poles and dedicated essential-services sections that enforce 110°C insulation.
- Protection device library with real catalogue records (Schneider Electric or NHP): MCB curves B / C / D, MCCB, ACB, RCD, RCBO and HRC fuses, with editable trip settings and a discrimination check between upstream and downstream devices.
- Maximum demand aggregated up the tree to AS/NZS 3000, with per-board diversity and spare capacity, single-phase load allocation across L1 / L2 / L3, and a check of total demand against the substation or grid supply capacity.
- Live issue list: every fault is named with the circuit it belongs to and the fix that resolves it, and clicking it jumps straight to the setting to change.
- Auto design sizes the cable and selects the protective device together, iterating until the two agree, with a global cap on auto-selected cable size.
- Links directly into the ElecAS calculator suite: cable size, voltage drop, voltage rise, maximum demand (Tables C1, C2, C3), generator sizing, UPS battery sizing.
- Export a branded PDF with the diagram, title block, legend, compliance summary and the cable, voltage drop, voltage rise, load, circuit breaker and switch schedules.
- Export to DXF (AutoCAD, Revit, BricsCAD) as fully editable CAD vectors (layers, symbols, cables and labels), so your drafting team drops the SLD straight into their sheets.
- Upload your own SVG symbols, auto-layout the diagram, and undo or redo any edit one step at a time.
- Tutorial mode walks first-time users through placing a source, switchboard, downstream loads, and exporting the diagram to PDF and DXF.
- A practical alternative to AutoCAD Electrical, ETAP, EasyPower, SmartDraw and Lucidchart for Australian electrical design.
How to draw a single line diagram in EleCAD
- Place the source and main switchboard: Open elecas.com.au/elecad, drag a supply source onto the canvas, then add the main switchboard. Tutorial mode walks first-time users through this exact flow.
- Add distribution boards and loads: Drag distribution boards, sub-boards, motors and loads onto the canvas and connect them. Each connection is a cable object carrying conductor, insulation and installation-method data.
- Set the protective devices: Assign MCBs (curve B, C or D), MCCBs, ACBs, RCDs, RCBOs or HRC fuses to each way from the Schneider Electric or NHP catalogue, and edit their ratings and trip settings in the switchboard editor. Add busbar sections where the board needs more than one bus.
- Enter cable and load data: Set conductor material (copper, flexible copper or aluminium), insulation (V-75, X-90, R-90, X-110 or R-110), phases, length, installation method, derating conditions and the number of parallel cable sets on each cable; set kW and power factor on each load. Demand, voltage drop, fault level and earth loop impedance update live.
- Clear the issue list: Work through the live issue list: each fault names the circuit it belongs to and the change that resolves it, and clicking it opens the setting to edit. Or leave cables and devices on Auto and let EleCAD size them together until every check passes.
- Export the diagram: Export a branded PDF carrying the diagram, title block, legend, compliance summary and the cable, voltage drop, voltage rise, load, circuit breaker and switch schedules, or a DXF that opens as editable geometry in AutoCAD, Revit and BricsCAD. Both are free with a free account.
EleCAD: drawing single line diagrams that carry real electrical data
A single line diagram builder made for AS/NZS design
EleCAD is a free, browser-based single line diagram (SLD) builder for Australian and New Zealand electrical design. You place sources, main switchboards, distribution boards, protective devices, cables and loads from a drag-and-drop palette, and the tool draws the diagram in Australian electrical drawing conventions. There is nothing to install and no licence to manage: the builder runs in any modern desktop browser.
Unlike a generic diagramming tool, every element is an electrical object. A cable is not just a line: it is a conductor with material, insulation, cores and an installation method. A distribution board tracks its incomer and outgoing ways; a protective device records its type and trip settings; a load carries kW and power factor. That is what lets the diagram drive calculations instead of merely documenting them.
The diagram stays live as the design changes
Change a downstream load and the upstream maximum demand updates. Change a cable run and the voltage drop, fault level and earth loop impedance all follow. Because the model knows the electrical relationships between components, edits propagate the way they do in the real design, which keeps the SLD, the calculations and the documentation in step through design development.
Every board reports not just its own voltage drop but the worst voltage drop anywhere in the tree below it, so the circuit that will fail the check is visible from the switchboard rather than found by opening each final subcircuit in turn.
What EleCAD checks on every circuit as you draw
These are not checks you run at the end. Each one is recomputed on every edit, and any failure appears in the issue list against the circuit it belongs to, with the change that resolves it.
| Check | Basis | What EleCAD uses to run it |
|---|---|---|
| Current-carrying capacity | AS/NZS 3008.1.1 | Published capacity tables for the conductor, insulation, cores and installation method, derated for ambient or soil temperature, soil thermal resistivity, depth of burial and grouping. |
| Voltage drop | AS/NZS 3000 Clause 3.6 | Per-segment drop from cable impedance and undiversified current, summed from the point of supply, against your site limit less the allowance reserved for final subcircuits. |
| Voltage rise | AS/NZS 4777.1 | Cumulative rise from the point of supply to each PV or battery inverter from its rated output, capped by the site export limit where one is set. |
| Prospective fault current | AS/NZS 3000 | Source impedance plus the accumulated cable impedance at every node, reported as both a maximum and a minimum three-phase fault level. |
| Earth fault loop impedance | AS/NZS 3000 Appendix B | The full R + jX loop including the earth conductor and its own parallel runs, checked against the trip current of the device actually fitted. |
| Short-circuit withstand | AS/NZS 3008.1.1 Table 5.1 | The adiabatic I²t ≤ k²S² check, run separately on the active conductor and on the earth conductor. |
| Breaking capacity | Device catalogue rating | The rated breaking capacity of the selected device against the prospective fault current where it is installed. |
| Discrimination | AS/NZS 3000 | The rating of each feeder device against every downstream device on the same path. |
| Maximum demand | AS/NZS 3000 Appendix C | Connected load aggregated up the tree with per-board diversity and spare capacity, then checked against the substation or grid supply capacity. |
Parallel cable sets, earth conductors and multi-section switchboards
Real submains are often more than one cable. EleCAD runs any circuit as multiple parallel sets, and the parallel count is carried through the physics rather than bolted on for display: active impedance, voltage drop, voltage rise and the earth fault loop are each divided across the runs. The earth conductor carries its own parallel count when it is not integral to the cable set, and can be sized automatically or fixed manually with an upper bound.
Switchboards are modelled as more than a single bus. A board can carry several busbar sections, tied together into sub-bus groups where the design calls for it, each with its own rating, incoming protection, RCD arrangement, connector device and spare pole allowance. Sections flagged as essential services enforce 110°C elastomeric insulation on the cables feeding them, so a fire-rated requirement cannot be lost between the diagram and the cable schedule.
Protective devices from a real catalogue, not a symbol library
Each protective device on the diagram is backed by a catalogue record from Schneider Electric or NHP, selectable per project. That record carries the trip characteristic the checks depend on: MCB curve B, C or D, the thermal or electronic trip settings on an MCCB or ACB, and the rated breaking capacity. It is why the earth fault loop check can be run against the trip current of the device actually specified rather than a generic assumption, and why breaking capacity can be tested against the fault level at that point in the network.
Auto design closes the loop between the cable and the device. Sizing a cable changes the fault level and loop impedance, which changes which device is acceptable, which in turn changes the current the cable must carry: EleCAD iterates the two together until they agree, subject to a global cap on auto-selected cable size that you set on the source.
Export: PDF for submissions, DXF for the drafting team
Diagrams export to a clean branded PDF for tender packages, design submissions and client review, and to DXF as fully editable CAD geometry with layers, symbols, cables and labels intact. The DXF opens directly in AutoCAD, Revit and BricsCAD, so a drafting team can drop the SLD straight into their sheets without redrawing it. Both exports are free and require only a free account to download.
Single line diagram terms explained
Single line diagram (SLD)
- A simplified schematic of an electrical installation that represents each circuit with one line and a standard symbol rather than drawing every phase conductor separately. In Australian practice the SLD is the primary design document, showing the supply, switchboards, protective devices, cables and loads and how they connect.
One-line diagram
- The North American term for a single line diagram. The two names describe the same drawing; Australian and New Zealand documentation to AS/NZS 3000 conventions normally uses "single line diagram" or "SLD".
Main switchboard (MSB)
- The switchboard at the origin of the installation, fed from the consumer mains, that houses the main switch and the protective devices for the submains. On an SLD it is the first board downstream of the point of supply.
Distribution board (DB)
- A downstream switchboard fed by a submain that distributes final subcircuits to loads. In EleCAD a distribution board tracks its incomer, busbar sections and outgoing ways, so its total connected load aggregates upstream to the maximum demand.
Submain
- The cable between two switchboards: typically from the main switchboard to a distribution board. Submains carry the aggregated demand of everything downstream, which is why their size follows from the maximum demand calculation rather than from any single load.
Final subcircuit
- The cable from a switchboard to the point of connection of the equipment it supplies, protected by the outgoing device on that way. Final subcircuits are the last segment of the SLD and the one where AS/NZS 3008.1.1 current-carrying capacity and voltage drop are checked against the connected load.
Protective device
- The circuit breaker, RCD, RCBO or fuse protecting a cable against overload, short circuit and, where required, earth fault. In EleCAD each device records its type, rating and trip characteristic (MCB curve B, C or D), which is what allows the diagram to carry discrimination and disconnection-time context rather than just a symbol.
Maximum demand
- The highest current an installation or submain is expected to draw, assessed under AS/NZS 3000:2018 Appendix C using Table C1 (domestic), Table C2 (non-domestic) or Table C3 (the energy method). It sets the size of the consumer mains, submains and their protection.
Busbar section
- A separately identified length of busbar within one switchboard, with its own rating, incoming protection and outgoing ways: for example a general bus, an essential-services bus and a metered bus in the same board. In EleCAD sections can be joined into sub-bus groups where they are tied or jointed, and a section flagged as essential services enforces 110°C elastomeric insulation on the cables that feed it.
Parallel cable sets
- Two or more identical cables run in parallel to carry one circuit, used when a single conductor of the required capacity would be impractical to install or terminate. Running n sets divides the circuit impedance by n, which reduces both the voltage drop and the earth fault loop impedance; EleCAD carries the parallel count through all of those calculations rather than only showing it on the drawing, and the earth conductor keeps its own parallel count when it is not integral to the cable set.
Voltage drop
- The fall in voltage along a cable caused by its impedance and the current it carries. AS/NZS 3000 Clause 3.6 limits the total drop from the point of supply to any point of connection. EleCAD computes it per segment from the undiversified current, sums it along the path, and lets you reserve part of the site allowance for final subcircuits so submains are not sized to consume the whole budget.
Voltage rise
- The increase in voltage along a cable when embedded generation pushes current back toward the supply, which is the reverse of voltage drop and the limit that governs PV and battery inverter connections under AS/NZS 4777.1. EleCAD accumulates the rise from the point of supply to each inverter from its rated output, and an optional site export limit caps the current on the consumer mains and so reduces the rise.
Prospective fault current
- The current that would flow in a bolted short circuit at a given point, set by the source impedance plus the impedance of every cable between the source and that point. It determines the breaking capacity a protective device must have. EleCAD computes it at every node in the diagram and reports both a maximum and a minimum value, since the maximum governs breaking capacity while the minimum governs whether a device will trip fast enough.
Earth fault loop impedance (Zs)
- The total impedance of the path a fault current takes from the active conductor, through the fault, back along the earth conductor to the source: the source impedance Ze plus the active and earth impedance of every cable in the path. It must be low enough for the protective device to disconnect within the time AS/NZS 3000 requires. EleCAD builds the loop from the full R + jX of each segment, includes the earth conductor and its parallel runs, and tests it against the trip current of the device actually specified.
Adiabatic short-circuit withstand
- The check that a conductor will not exceed its permitted temperature during the time a fault takes to clear, expressed as I²t ≤ k²S² where k is the material and insulation constant from AS/NZS 3008.1.1 Table 5.1 and S is the conductor cross-sectional area. EleCAD runs it separately on the active conductor and on the earth conductor, because the earth is often the smaller of the two and is therefore the one that fails first.
Discrimination
- Also called selectivity: the arrangement of protective devices so that a fault is cleared by the device closest to it, leaving everything upstream energised. Losing discrimination means a single final subcircuit fault trips the main switch and blacks out the installation. EleCAD flags any feeder device rated at or below a device downstream of it on the same path.
Diversity
- The allowance made for the fact that not all connected load runs simultaneously, applied so that consumer mains and submains are sized for realistic maximum demand rather than the arithmetic sum of every load. In EleCAD diversity is set per board and applied to that board's children, with a separate spare-capacity allowance that can be diversified or not.
Derating
- The reduction applied to a cable's tabulated current-carrying capacity to account for the conditions it is actually installed in: ambient air or soil temperature, soil thermal resistivity, depth of burial, and grouping with other circuits. AS/NZS 3008.1.1 publishes a factor for each. EleCAD applies them per cable, so a run grouped in a hot ceiling space is sized differently from the same run in free air.
DXF export
- Drawing Exchange Format: a vector CAD file format that AutoCAD, Revit, BricsCAD and other CAD packages open as fully editable geometry. Exporting an SLD to DXF preserves layers, symbols, cables and labels, so a drafting team can place the diagram directly onto a sheet without redrawing it.
Point of supply
- The point at which the electricity distributor's network ends and the consumer's installation begins, normally at the network meter or the origin of the consumer mains. On an SLD it is where the supply source is drawn and where earth fault loop impedance and voltage drop budgets start.
Single line diagram software: frequently asked questions
What is a single line diagram?
- A single line diagram (SLD), also called a one-line diagram, is a simplified schematic of an electrical power system that shows components (sources, switchboards, protective devices, cables and loads) using single lines and standard symbols instead of separate phase conductors. SLDs are the primary design and reference document for electrical installations in Australia, used for design submissions, tender drawings, switchboard schedules, commissioning and as-builts.
Is EleCAD free?
- Yes: EleCAD is free to use in your browser. Drawing and editing a single line diagram needs no account at all. Downloading the diagram as a PDF or DXF requires a free ElecAS account, and the download itself stays free with no watermark and no export cap. The paid Pro plan adds cloud save and sync across devices, project workspaces and folders, and your own logo and accent colour on exported PDFs.
Does EleCAD work in the browser without installing software?
- Yes. EleCAD runs entirely in the browser: Chrome, Edge, Safari and Firefox are all supported. There is nothing to download, no licence file to install, and no plug-in to enable. Diagrams are rendered locally so it works on any desktop or laptop, including locked-down corporate machines.
Does EleCAD work on a phone or tablet?
- No: EleCAD is a desktop and laptop tool. The canvas, palette and properties panel need a browser window at least 1024 pixels wide, so phones and smaller tablets are shown a prompt to reopen the page on a larger screen instead of a cramped canvas. The rest of the ElecAS calculator suite works on any screen size.
Can I export EleCAD single line diagrams to PDF or DXF?
- Yes. EleCAD exports your single line diagram to a clean, branded PDF suitable for design submissions, tender packages, client review and project files: the PDF includes the diagram, project details and a switchboard / device schedule. It also exports to DXF, which opens directly in AutoCAD, Revit, BricsCAD and other CAD packages as fully editable vector geometry (layers, symbols, cables and labels), so your drafting team can drop the SLD straight into their sheets.
EleCAD vs AutoCAD Electrical: what is the difference?
- AutoCAD Electrical is a heavyweight desktop CAD package licensed per seat: it is excellent for detailed schematics, panel layouts and large industrial projects but has a steep learning curve and high cost. EleCAD is a free, browser-based SLD builder focused on Australian single line diagrams and early-stage design: quick to learn, no install, and integrated with the ElecAS calculator suite. EleCAD is the right tool for concept SLDs, tender drawings, small-to-medium projects and any time AutoCAD would be overkill. The two also work together: EleCAD exports to DXF, so you can draft an SLD in the browser in minutes and open it in AutoCAD as fully editable geometry to finish it off.
EleCAD vs SmartDraw or Lucidchart for single line diagrams?
- SmartDraw and Lucidchart are general-purpose diagramming tools: they have electrical symbol libraries but no electrical engineering intelligence. EleCAD understands the actual electrical relationships: switchboards have busbars and incomers, cables have conductor material and installation method, loads contribute to maximum demand, protective devices have trip curves. That makes EleCAD substantially faster for real electrical design, with fewer mistakes carried into the calculations.
What symbols and components does EleCAD support?
- The palette places a supply source (utility connection or substation), switchboards, additional busbar sections, general loads, PV / battery inverters, spare poles, and a bundle that drops a repeated set of unit supply circuits in one go. Devices are then placed inline on any busbar or cable: isolators and switches, circuit breakers (MCB curves B / C / D, MCCB, ACB), RCDs and RCBOs, HRC fuses, supply authority and multi-function meters in direct or CT connection, MEN links and surge diverters. You can also upload your own SVG symbols to use as custom blocks. New symbols are added based on user requests via the Contact page.
Does EleCAD link to cable sizing and maximum demand calculations?
- It does more than link to them: it runs them. Every cable in EleCAD is sized by the same AS/NZS 3008.1.1 selection engine that powers the ElecAS Cable Size Calculator, reading the same published capacity, derating and impedance tables and the same circuit protection database, so a run sized on the diagram and the same run entered into the calculator return the same answer. Loads aggregate up the tree into the AS/NZS 3000 maximum demand at each board, and voltage drop, voltage rise, fault level and earth fault loop impedance are all computed on the diagram itself rather than being re-entered somewhere else.
Can I share or collaborate on diagrams?
- Diagrams are shared today by export: a branded PDF for review and submission, or a DXF your drafting team can open in AutoCAD, Revit or BricsCAD and edit directly. Real-time multi-user collaboration is on the roadmap: sign in to your ElecAS account to be notified when it ships.
Is EleCAD suitable for AS/NZS 3000 design submissions?
- EleCAD is suitable for the single line diagram component of an AS/NZS 3000 design submission, tender package or as-built drawing set. As with any electrical design tool, the user remains the engineer of record: every diagram, calculation and design decision must be reviewed and signed off by a qualified electrical professional before issue, construction or energisation. See the Verification page for the engineering review process behind ElecAS.