Electrical Wiring Simulator & Trainer

The Electrical Wiring Simulator is a hands-on domestic installation trainer. You place realistic components — a consumer unit with breakers, one-way and two-way wall switches, 13 A sockets, ceiling roses, lamp holders and household appliances — onto a workbench, then wire them together with true multicore cables. Each cable end fans out into its individual coloured conductor nodes (brown Line, blue Neutral, green-yellow Earth), exactly like stripping a real cable. Turn the power on and the circuit comes alive: lamps light, fans spin, breakers trip and overloaded cables overheat.

It is built for electrical trainees, vocational students and instructors who want to practise wiring safely before touching real conductors.

• Add a component: tap a palette item to drop it on the board, or drag it straight from the palette to the exact spot you want. Either way you can drag it again on the board to reposition.
• Protect a section: drop an MCB Breaker in-line on a circuit's Line conductor (In → Out) and set its rating — it trips if that section is overloaded; tap it to reset.
• Join many wires: use a Connector Block as a distributor — all its terminals are one common node, so you can branch one connection (Line, Neutral or Earth) out to several conductors. Select it and press ↻ Rotate 90° (inspector or toolbar, or R) to turn it to any of four orientations so it lines up neatly with your wiring.
• Add a cable: in the Cable Builder pick a core type (e.g. Twin & Earth) and a size, then press Add Cable. The cable appears with coloured conductor nodes at each end.
• Wire it up: drag a conductor node (the small coloured dot at a cable tip) onto a component terminal to make a connection.
• Join two wires: drag one conductor tip onto another conductor's tip — an insulator connector appears over the splice. Click that connector (or tap either connected conductor) to open the joint again.
• Bend & route a cable: select a cable and grab the round anchor just past either end. Drag it along the cable to extend that side, or drag it sideways (90°) and the cable folds a right-angle corner and continues in that direction — keep dragging and turning to add more corners. Drag the cable body to move the whole run, drag a corner to reshape it (right-click a corner to remove it), and use the ↻ button (or R) to rotate 90°.
• Plug in an appliance: in the Cable Builder pick Power cord — 3-pin plug, add it, and wire its bare end into an appliance's L, N, E. Then drag its moulded 3-pin plug onto a 13A socket — it seats in the face and connects Line, Neutral and Earth automatically. Tap the socket to flip its switch — the red neon glows when it is switched on and live, and the appliance only runs when the socket is on.
• Energise: press Power ON. Toggle switches by tapping them.
• Edit tools (bottom of the canvas): Undo, Redo, Duplicate, Rotate cable, Delete and Clear.
• Left panel: the Selected Item inspector sits at the top and opens automatically when you select something on the board (and folds away when nothing is selected); below it, Components and Household Loads are collapsible sections — click a heading to fold it away.
• Keyboard: Ctrl+Z undo, Ctrl+Shift+Z (or Ctrl+Y) redo, Ctrl+D duplicate, R rotate a selected cable, Delete delete (Shift+Delete clears the board), P power, G generate.
• Save / Open: use Save to download your circuit as a .json file and Open to load one back later — handy for sharing or resuming work.
• Fullscreen: the Fullscreen button (or F) expands the workbench to fill the screen.
• Examples: pick a circuit from the Load an example menu and it loads instantly, fully wired, for you to study or modify.

Simulate is the wiring workbench. The toolbar gives you Power, an example-circuit menu, a 230 V / 120 V supply toggle, and Save / Open / Fullscreen; the in-canvas tools handle undo, redo, duplicate, rotate, delete and clear. The readout badges show supply voltage, total load current, how many loads are live, and overall status. The fault strip lists any wiring problems it detects:

• Overloaded cable — current exceeds the cable's rating; it heats up and, if the protective device is too big, catches fire. Both the Line and the Neutral conductors carry the load current, so an undersized neutral overheats too.
• Breaker tripped — overload (thermal, after a short delay) or a Line-Neutral short (instant magnetic trip). On a short the nearest protective device operates: a plug fuse or spur fuse blows before the main breaker trips (discrimination).
• Earth fault — Line touching Earth trips the 30 mA RCD; with no RCD fitted, the heavy fault current trips the breaker instead, and the tool explains why an RCD would be safer.
• Neutral–Earth fault — a Neutral connected to Earth trips the RCD as soon as a load draws current; without an RCD it goes unnoticed, which is exactly why it is dangerous.
• Reversed polarity — a load wired with Line and Neutral swapped still runs (AC does not care), but the tool flags it as a danger: the appliance's own switch and fuse end up in the Neutral.
• Missing earth — a metal-bodied (Class I) appliance with no protective earth is a shock hazard.
• Switched neutral — the switch breaks the neutral instead of the line.
• Wrong / blown plug fuse — every 3-pin power cord carries its own BS 1363 plug fuse (3, 5 or 13 A, set in the cable inspector). A fuse bigger than the flex is flagged; a sustained overload blows the fuse, and you replace it from the inspector.
• Socket overloaded — sockets are rated 13, 16 or 32 A (set in the inspector). Draw more than the rating through a socket and its contacts overheat — fit a 32 A socket, or feed fixed heavy loads like a water heater through a Fused Spur (fuse options now up to 32 A).

In a ring final circuit the readouts show the current genuinely dividing between the two legs of the ring — the shorter leg carries proportionally more — so you can see why a ring lets a 2.5 mm² cable serve a 32 A breaker.

Real installations use multicore sheathed cable, not loose wires. The Cable Builder lets you choose:

• Core type: single-core (individual Line, Neutral or Earth conductors — as used in conduit/trunking or for earth bonding), 2-core (Line + Neutral), Twin & Earth (+ bare earth), 3-core + earth (for two-way switching), and 2-core / 3-core flex for appliances.
• Size: metric mm² (1.0, 1.5, 2.5, 4, 6, 10) or the equivalent SWG number, each showing its current rating. Pick a size whose rating exceeds the load current from I = P / V.

The golden rule the simulator grades against is I_load ≤ I_device ≤ I_cable: the fuse or breaker must be bigger than the running current but smaller than the cable rating.

Explore organises the theory into four categories: Wire & Cable (SWG, mm², ratings, core colours), Components (switches, sockets, consumer unit, FCU), Protection & Safety (MCB, RCD, earthing, fuses) and Circuits (one-way, two-way, ring/radial, loop-in). Each card has a clear explanation and, where relevant, a worked example.

Practice mode mixes calculation problems (find the load current, pick the cable, size the fuse) with wiring-choice questions. Type or choose your answer, press Check, and read the worked solution. Your score is tracked.

Quiz mode presents 5 questions on cable sizing, colours, switching and protection, then gives a score with a star rating and a per-question breakdown.

Every current in the tool comes from I = P / V. Example: a 2000 W heater at 230 V draws 2000 / 230 ≈ 8.7 A, so a 1.5 mm² flex (16 A) with a 13 A plug fuse is safe. The same heater on a US 120 V supply would draw 16.7 A — nearly double — which is why the 120 V toggle recomputes every current.

Safety: all current ratings here are teaching nominals. Real installations must be sized and derated per BS 7671 / local code. This simulator is an educational aid, not a substitute for a qualified electrician.