A design aid.
Not the code book.
Lastsocket is a design aid. It does not replace the applicable installation standard, manufacturer data, or a qualified person’s judgement. Verify tabulated current-carrying capacity in your current code book.
This page says what every number in the app is made of, what the app does not check, and how the numbers are tested.
Conductor resistance
IEC 60228 maximum DC resistance at 20 °C per cross-section, for copper and aluminium, corrected to the conductor’s operating temperature — 70 °C for PVC, 90 °C for XLPE — with α = 0.00393 /K for copper and 0.00403 /K for aluminium. Voltage drop is calculated at operating temperature by default; a 20 °C option exists, is labelled optimistic, and is only valid for a lightly loaded cable. A calculator that uses 20 °C under-reads the drop by about 20 %.
Limits per pack
All five packs are free. A pack changes the limit, the labels and the rule cited — never the formula. This table is generated from the app’s pack files.
| Pack | Lighting | Other | Cited as |
|---|---|---|---|
| IEC typical | 3 % | 5 % | IEC 60364-5-52 cl. 525 |
| NEN 1010 (NL) | 3 % | 5 % | NEN 1010 §525 |
| BS 7671 (UK / IE) | 3 % public · 6 % private | 5 % public · 8 % private | BS 7671 Appendix 4 Table 4Ab |
| DIN VDE 0100 (DE) | 3 % | 3 % | DIN 18015-1 |
| NF C 15-100 (FR) | 3 % | 5 % | NF C 15-100 §525 |
Current-carrying capacity
The bundled values are a small subset consistent with IEC 60364-5-52 Annex B — methods A1, B2, C and E, PVC copper, to 50 mm² — not a reproduction of any national table, and not every case in your standard. That sentence is generated from the app’s grid, so it can never claim more than the app holds. Always confirm Iz in the current edition of your installation standard and the cable manufacturer’s data. Correction factors for ambient temperature, grouping and thermal insulation are applied by Pro; your own Iz can always be typed for free.
Pipe, loss, expansion, heat
Pipe size by continuity, di = √(4Q / πv), compared against the catalogue’s inner diameter. Pressure loss by Darcy-Weisbach with a Swamee–Jain friction factor, water at 10 °C, roughness by material. Linear expansion with typical α per material. Room heat loss as envelope plus ventilation, Φ = Σ(A · U · ΔT) + 0.33 · n · V · ΔT — a simplified estimate, not EN 12831. Velocity figures are good practice, not a code clause.
What the app does not check
- Short-circuit withstand
- Earth-fault loop impedance and disconnection time
- Conduit and trunking fill
- Thermal bridges, solar gains or intermittent heating in the heat-loss estimate
Each of these needs a measured value or a licensed table. The app says so in every working card rather than guessing.
Why packs are free and tables are not
If you type it or pick it, it’s free. If the app looks up a table or walks the sizes for you, it’s Pro. A national pack is something you pick, so every pack is free. Current-carrying-capacity tables, correction factors, pipe catalogues and construction presets are things the app looks up, so they are the €9.99 unlock — once.
Engine version and test vectors
Every figure on this site is generated from the app’s own export, and the site’s voltage-drop calculator is checked against the app’s test vectors and a few thousand exported cases on every build. A change to the physics changes the engine version, which is printed on every saved calculation and at the bottom of every page. Current engine: 1.