Single-Line Diagram

ElectroBoard generates a single-line diagram (SLD) from your panel automatically. It is the standard engineering document: it shows how circuits are electrically connected, using IEC 60617 graphical symbols.

📌 How it differs from the panel layout: The layout view (the main editor) shows the physical arrangement of devices on the DIN rail. The SLD shows how the circuits are wired — this is the document an inspector, a client or a design package actually asks for.

---

Opening the SLD#

1. Open any panel project in the editor
2. Click "Export ▾" in the toolbar
3. Choose "Single-line diagram"

Or navigate straight to: /board/[id]/schematic

[screenshot: Export menu with the "Single-line diagram" item]

---

What the Diagram Shows#

Busbars (horizontal lines)#

• Phase busbars — L1, L2, L3 — drawn along the top. Their colours follow the conductor-marking standard selected for the panel: IEC (brown / black / grey), the post-Soviet convention (yellow / green / red) or NEC (black / red / blue). Change the standard in the panel and the busbars are repainted.
• Neutral busbar N (blue) — along the bottom, always present
• Protective earth busbar PE (green) — along the bottom, only if the panel actually contains a PE bar. No PE bar means no PE line on the diagram, and no device gets an earth connection. That is not a drawing glitch — it is an exact reflection of what has been assembled in the panel.

Only terminal devices (those with no children) connect to PE, and only those device types for which a protective conductor makes sense — a socket outlet or an SPD, for example. Intermediate RCDs and isolators do not consume PE.

Devices#

Every device is drawn with its own symbol. Symbol width grows with the pole count: a two-pole MCB is wider than a single-pole one, a three-phase device wider still. The vertical stubs above and below each symbol correspond to the device's real poles.

Twenty device types have a dedicated graphical symbol:

Device	Symbol on the diagram
MCB (miniature CB)	Switching contact with terminal circles
RCD / RCCB	Residual-current transformer rectangle
RCBO	Residual-current transformer + MCB contact
Isolator / switch-disconnector	Break contact with terminal circles
Fuse	Fuse-element rectangle
SPD	Varistor rectangle with an earth tap
Energy meter	Circle with terminals
Contactor	Contact + control-coil rectangle
AFDD (arc fault detection)	Rectangle with an arc mark
ATS (changeover unit)	Rectangle with two inputs
Voltage relay	Relay rectangle
Multifunction relay	Relay rectangle
LED driver	Converter rectangle
DC power supply	Converter rectangle
Terminal block	Square with a connection dot
Smart control module	Rectangle with a letter mark
Dimmer	Rectangle with a letter mark
Bell / buzzer	Rectangle with a letter mark
Indicator lamp	Circle with a cross
DIN-rail socket outlet	Socket-outlet symbol

The remaining types — time relay, current relay, phase-failure relay, cross-connection module, smart switch, 1-0-1 changeover switch, phase selector, blanking plate and generic custom device — are drawn as a plain rectangle with vertical stubs matching the pole count. The diagram loses no electrical correctness: the device is there, its poles and connections are shown. It simply has no bespoke graphic yet.

[screenshot: diagram fragment — MCB, RCD, RCBO and SPD side by side]

Labels#

Up to four texts can be shown next to each device:

• Load name — the full text, never truncated (for example, "Refrigerator, lower section"). It sits above the symbol by default; orientation is horizontal or vertical.
• Rating — a single line under the symbol: trip curve and current together (C16A). For RCDs and RCBOs the residual current is appended: C16A 30mA. The curve letter is never drawn on its own — it always shares the line with the rating, otherwise the letter would sit on top of the outgoing conductor.
• Consumers — if you have entered them: a comma-separated list truncated at 22 characters (an ellipsis follows). So "Kitchen sockets, hood, dishwasher" appears as "Kitchen sockets, hood…". If you need the full list on paper, move it into the load name.
• Group caption — the parent device's name, in italics above the dashed group frame.

Placeholder names ("MCB", "RCBO (9)" — the default names a device inherits from the registry) are hidden automatically: they carry no information for an electrician and only clutter the sheet. The "Placeholder names" checkbox in the settings strip brings them all back at once; a single node can be given its name back from its popover.

Connections#

• Solid lines — phase conductors, drawn in the colour of the conductor
• Dashed lines — connections to the N and PE busbars
• Dashed frame — a group of devices sitting under one RCD or RCBO

---

Protection Groups (RCD + downstream MCBs)#

If you have defined a hierarchy (an RCD or RCBO with child MCBs), the SLD renders it as a group:

      [RCD 2P 30mA]
      ┌─────────────────────┐
      │                     │
   [MCB C16]           [MCB C10]
   Kitchen sockets     Washing machine

A dashed frame encloses the whole group. Child devices are spread evenly under their parent.

[screenshot: an RCD group with its child MCBs]

---

Phase Configuration#

The diagram adapts to the panel's phase configuration automatically:

Single-phase panel — one phase busbar (L1) on top:

L1 ──────────────────────────────────
    │          │          │
  [QS]      [QF1]     [RCD]─┬─[QF2]
                              └─[QF3]
N  ──────────────────────────────────
PE ──────────────────────────────────

Two-phase panel — two phase busbars L1/L2 on top plus the neutral N. Use this for split-phase supplies: the incomer arrives on two lines taken from different phases, with no third phase present.

Three-phase panel — three busbars L1/L2/L3 on top, and every device taps only the phases it actually uses.

The phase configuration is read from the panel's own settings — there is nothing to set on the diagram itself. Change it in the editor and the diagram rebuilds.

---

Multiple Supplies#

If the panel is fed from several independent sources (utility supply plus a standby generator, a UPS, a solar inverter), the SLD draws a separate block for each source, with its own busbars and drop lines to the devices it feeds.

Supported source types:

Source	How it looks on the diagram	Purpose
Utility grid	Caption only, no frame	Primary external supply
Transformer	Symbol in a frame, blue tint	Supply from a dedicated substation
Generator	Symbol in a frame, orange tint	Standby engine-driven supply
Inverter	Symbol in a frame, green tint	DC-to-AC conversion
UPS	Symbol in a frame, purple tint	Uninterruptible supply
Solar array	Symbol in a frame, yellow tint	Photovoltaic modules as a source
Battery	Symbol in a frame, green tint	Storage
Other source	Generic symbol in a frame, grey tint	Anything the types above do not cover

What happens automatically:

• Every source except the utility grid is drawn as a framed block with a symbol and a caption. The grid is drawn without a frame — it is the primary supply and needs no visual emphasis.
• Each source gets its own busbars. Generator power is never merged onto the same line as utility power. That distinction matters: on paper it must be visible that the standby circuit is electrically separate until a changeover device transfers the load.
• Pole by pole. On a multi-pole 1-0-1 changeover switch, each pole gets its own line to the matching phase of its own source. On an ATS, the secondary input arrives from the standby source.
• The drop line from a source busbar to a device runs inside that source's frame — so it is immediately obvious which device is fed from which supply.

How to enable it: add a 1-0-1 changeover switch or an ATS to the panel, or mark a device in its properties as being fed from a generator, a UPS or an inverter. The SLD finds the sources and builds their busbars on its own — there is nothing to configure by hand.

The source caption comes from the name you typed into the device's properties. Leave it empty and a default is used ("Generator", "UPS").

[screenshot: SLD with grid + generator + UPS — three separate source blocks]

---

Label Settings (the strip above the diagram)#

A settings strip sits above the diagram. Changes apply instantly, both on screen and in print:

• Font — load-name size, 6–14 pt in steps of 0.5 (9 pt by default).
• Orientation — horizontal (default) or vertical: names rotate by 90°, which rescues panels with many narrow columns.
• Sheet — A4 landscape (default) / A4 portrait / A3 landscape. Determines the page size used for printing.
• Bold — semi-bold load names (off by default).
• Phase rails (L1/L2/L3/N) — captions for the phase and neutral busbars, to the left of the horizontal lines (on by default).
• Group captions — the parent device's name above the dashed frame (on by default).
• Placeholder names — show the default names inherited from the device registry (off by default).
• Rating — the C16A line under the symbol (on by default).
• Trip curve (B/C/D) — prepend the curve letter to the rating (on by default). Turn it off and 16A remains.
• Consumers — the small list below the rating (on by default).
• "Reset" — asks for confirmation, then returns every setting to its default and erases all per-device changes, including any labels you have dragged.

[screenshot: the settings strip above the SLD]

Per-Device Settings (popover)#

Clicking any symbol or any of its labels opens a popover on the right. Everything you change there applies to that device only and overrides the global strip:

• Orientation — horizontal / vertical
• Font — 6–14 pt
• Bold — "Default" / "Yes" / "No"
• Show rating, Trip curve, Consumers — the same three states
• Name — "Yes" forces even a placeholder name to appear when placeholders are globally hidden; "No" hides this device's name while every other name stays visible
• "Reset label positions" — the button appears only when this device has labels that were dragged
• "Reset this device" — drops every per-device setting; the device obeys the global strip again
• "Close"

The popover closes on a click outside it and never appears in print.

[screenshot: the per-device settings popover]

Dragging Labels#

Every text on the diagram — the name, the rating, the consumer list, the group caption — can be dragged within a bounded zone around its device:

• A click without movement opens the settings popover.
• Movement beyond 5 px is a drag. On release, the label snaps to a 5 px grid, so neighbouring texts line up with each other on their own.
• Keyboard. Focus a text (Tab) and move it with the arrow keys in 5 px steps, or Shift+arrow in 25 px steps. Enter or Space opens the popover. This is the only way to place a label with pixel precision.
• While you drag, a thin blue dashed frame appears — that is the permitted zone.
• The zone differs per text. The name sits above the symbol, so it is allowed more travel downwards; the rating and the consumer list sit below the symbol, so they are allowed more travel upwards. Horizontally all of them may move about 80 px either side of the symbol edge. The group caption travels along the top edge of the frame and below it.
• If a system interruption happens mid-drag — an incoming call, a back gesture, an app switch — the move is discarded and the label stays where it was. That way no accidental offset ever reaches the printed sheet.
• The grab area of a text is never smaller than 44×44 px, so a label can be caught with a finger on a tablet.

💡 Why this exists: on a busy diagram labels inevitably collide with conductors and neighbouring symbols. An electrician works from a printed sheet — everything there has to read at a glance. Dragging lets you scatter the texts into the free gaps between components, and exactly as you arranged them is exactly how they print.

Navigating the Diagram#

• Mouse wheel — zoom
• Drag the background — pan
• On a touch screen — pinch to zoom, one finger to pan

Zooming and panning change only your view of the sheet. They never alter the diagram itself, and they have no effect on what gets printed.

Where the Settings Live#

All strip settings, all per-device settings and the positions of every dragged label are stored in your browser, separately for each project. Open a different panel and it carries its own set of settings.

The consequence is worth knowing: these settings do not travel with the diagram. If you open the project in a different browser or on a different computer, or send a colleague a shared-view link, the diagram is rendered with the defaults — without your dragged labels. To hand over the view exactly as you arranged it, print to PDF and send the file.

---

Printing and Saving the SLD#

Press the "Print" button in the strip. Ctrl+P works too. The paper size and orientation follow the "Sheet" setting:

• A4 landscape (default) — 297×210 mm, for typical panels
• A4 portrait — 210×297 mm, for narrow single-phase panels with a deep hierarchy
• A3 landscape — 420×297 mm, for wide panels that will not fit on A4

In the print dialog choose "Save as PDF" — that gives you a vector file for the project package.

The diagram compresses when printed. During printing the SLD switches to a dense mode: the vertical step between hierarchy levels drops from 110 to 70 px, the horizontal gap between neighbouring devices from 50 to 32 px, and the lines are rendered crisper. Considerably more therefore fits on the sheet than the screen suggests. Once the print dialog closes, normal spacing returns.

The SLD always prints in the light theme — even when the editor is in dark mode. It is a paper-style view: white background, black text, tuned for an office printer. Page margins are removed, the settings strip and popovers stay off the sheet, and a header with the logo and the project name appears at the top instead.

Tip: for very large panels, try combinations — A3 landscape together with vertical label orientation gives the most room.

---

Current Limitations#

• There is no one-click PDF export. A PDF is produced through the browser's print dialog ("Save as PDF"). Neither quality nor vector fidelity suffers, but it is an extra step.
• There is no circuit numbering or bill of materials. Devices carry no QF1 / QF2 style designations, and the diagram is not accompanied by a parts table.
• Not every device type has a dedicated graphical symbol — see the list above; the rest are drawn as a plain rectangle.
• Label settings live in your browser and are not carried along with the diagram.

Hierarchy depth is not limited: isolator → RCD → MCB → contactor renders correctly, each level with its own group frame.

Symbols follow IEC 60617; the installation principles the diagram is meant to document (protective earthing, disconnection, discrimination between protective devices) are those of IEC 60364.

If you have remarks or suggestions, write to us: eBoard_UA