Every socket, fixture and appliance you drop onto the electrical & plumbing layer is connected to a circuit. The simulation adds up the circuit's power and calculates the current, a suitable breaker, the cable size and the voltage drop at the end of the line. The calculation runs inside the editor the moment you finish wiring; an overloaded line lights up red on the plan, so you see it before you even call the electrician.
The simulation runs inside the editor, right after the electrical & plumbing layer: it reads the symbols, you confirm the power ratings, and the rest is automatic. Results are listed circuit by circuit in the simulation step; the report can be printed or downloaded as CSV.
Every symbol has a power rating: socket 300 W, double socket 600 W, light fixture 60 W, oven 3,000 W, induction hob 7,200 W. A socket next to a washing machine or oven counts as that appliance. The total of the symbols on a circuit is converted into a design current; you can change the value in the right panel to match your own appliance.
The smallest standard circuit breaker that carries the design current is suggested: B6, B10, B16, B20, B25, B32. When breaker load exceeds 80% you get a yellow warning, above 100% a red one.
It checks that the suggested breaker does not exceed the cable's current-carrying capacity. 1.5 mm² for lighting, 2.5 mm² for sockets, 4–6 mm² for oven and hob, 10–16 mm² for the supply riser.
The circuit's length is measured on the plan and the voltage drop at the end of the line is calculated. If it exceeds 1.5% on lighting or 3% on socket and power circuits, a larger cable size or splitting the circuit is suggested.
Not all appliances run at the same time. Circuit loads are summed with a demand factor (0.6–0.7 for an apartment), and the supply riser size and main switch (C40, C63) are suggested accordingly. The RCD is fixed at 30 mA.
Oven and washing machine on the same circuit, more than eight sockets on one socket circuit, a line without RCD protection in a wet area, a lighting circuit longer than 25 metres, a line passing through a reinforced concrete column or beam: all are marked on the plan; a route around the column recalculates the take-off and the voltage drop. Column–wiring check →
The values the simulation uses by default. The circuit type is worked out automatically from the connected loads (a socket next to the oven becomes an oven circuit); you can change it in the circuit's properties.
| Circuit | Cable | Breaker | Note |
|---|---|---|---|
| Lighting | |||
| Room lighting circuit | 3 × 1.5 mm² | B10 | One or two rooms combined; up to 12 light fixtures |
| Socket | |||
| General socket circuit | 3 × 2.5 mm² | B16 | Up to 8 sockets per circuit; a separate circuit per room is recommended |
| Kitchen worktop sockets | 3 × 2.5 mm² | B16 | Separate circuit; small appliances go here |
| Washing machine | 3 × 2.5 mm² | B16 | Each machine on its own circuit |
| Dishwasher | 3 × 2.5 mm² | B16 | Each machine on its own circuit |
| Power | |||
| Oven / built-in hob | 3 × 4 mm² · induction 3 × 6 mm² | B20 · B32 | Separate circuit, direct connection or power socket |
| Air conditioner | 3 × 2.5 mm² | B16 | Separate circuit for each indoor unit; mind the distance to the outdoor unit |
| Water heater / electric heater | 3 × 2.5 mm² | B16 | Separate circuit; RCD protection mandatory in wet areas |
| Combi boiler | 3 × 1.5 mm² | B10 | Separate circuit, earthed |
| Distribution board | |||
| RCD | — | 30 mA | All socket and wet-area circuits; a separate RCD is recommended for lighting |
| Supply riser (meter → board) | 3 × 10 mm² · 3 × 16 mm² | C40 · C63 | Based on the total load found with the demand factor; 5 cores for three phase |
The values reflect common residential practice; local regulations, the utility company's specifications and the engineer's decision take precedence. Aluminium conductors, surface installation and high ambient temperatures reduce capacity.
Place the distribution board on the electrical & plumbing layer and run lines to the rooms with the circuit tool. When a circuit point lands on a symbol, the symbol is connected to that line; you can change which breaker feeds it in the circuit's properties. The circuit type (lighting, socket, power) determines the cable and the breaker.
Every symbol comes with a default power rating. Type the value from the oven's label or the air conditioner's BTU rating into the right panel; the simulation recalculates instantly. For appliances you're unsure about, a typical value is suggested.
The circuit list gives the current, breaker, cable size and voltage drop; any line over the limit lights up red on the plan. The board schematic and breaker list are added to the MEP sheet as a PDF, and that is what goes to the electrician.
With a separate calculator, you enter the length as a guess. Nodaform measures circuit length from the line you draw on the plan and groups symbols by room; when you move furniture and shift a socket, the calculation updates itself.
Plan and furniture layers. The electrical & plumbing tab is locked; you can review the distribution table on this page.
Electrical & plumbing layer: sockets, switches, lighting, distribution board and circuit schematic; wall view in 3D. No load calculation.
MEP sheet, cable take-off and breaker list; default cables and breakers are assigned by circuit type, with no calculation.
Plan-linked load, breaker, cable size and voltage drop simulation; warnings on the plan, board schematic, written to BIM properties.
The design current is found from the circuit's total power; the smallest standard breaker that carries that current is chosen and checked against the cable's current-carrying capacity. Voltage drop is calculated from line length and cable size.
Nodaform uses 1.5% for lighting circuits and 3% for socket and power circuits as warning thresholds. For a line over the limit, a larger cable size or a shorter line is suggested.
Yes. When you select a three-phase supply, circuits are balanced across the phases; large loads such as the oven and air conditioner are put on separate phases. Phase balance is shown as a percentage in the simulation panel.
No. The results are a pre-check to discuss with your electrician and electrical engineer; the construction design and approval belong to a licensed engineer.
Plan-linked voltage and load simulation is on the Ultimate plan; it runs in the editor right after the electrical & plumbing layer, without opening a separate tool.
Open a free account, draw the plan and drop in the sockets. Once Ultimate is unlocked, breaker and cable size calculations come in one click on the same plan.