EV Wallbox Cable Size & Load Management: 11 kW vs 22 kW

Balanced three-phase AC input is $P=\sqrt{3}U_{LL}I$ at unity power factor. ABB's 11 kW and 22 kW wallbox classes use 16 A and 32 A per phase. Their rounded nameplate classes are used for NAV screening; physical power is calculated at the entered voltage.

Connection headroom is $I_h=I_{main}-I_{other}-I_{reserve}$ on the busiest phase. Without load management the bank demands all vehicle-limited branch currents. Static control divides a fixed bank cap between vehicles; check that cap against the design peak of other loads. The static-cap safety screen limits possible bank demand to the smaller of the cap and installed wallbox hardware capacity; it does not rely on the vehicles' present current limits. Dynamic control uses the entered present snapshot of other loads. Equal sharing gives $I_{share}=\min(I_{rated},I_{car},I_{bank}/N)$. Below 6 A per vehicle, all modelled chargers pause. Schneider Electric's load-management guide defines the two control methods; its commissioning guide documents the IEC 61851 minimum of 6 A. The dynamic chart uses exact full-current and 6 A pause thresholds. Its repeated pause coordinate draws a vertical drop to zero; below-minimum charging powers are not interpolated across that transition. A negative other-load threshold means that operating region is already unavailable with no other loads. A real controller must measure each phase and handle communications loss safely.

For each separate final circuit, class 2 plain copper resistance at 20 °C comes from the platform wires.metric data (IEC 60228:2004). Candidate resistance data come from manufacturer Damai, NYY 1. Copper temperature correction is $R_\theta=R_{20}(1+0.00393\Delta T)$, consistent with the platform copper material data (IEC 60028). Damai's independently published 70 °C values provide checks. With one-way length in kilometres, $\Delta U_{LL}=\sqrt{3}I R_\theta L$ and $P_{loss}=3I^2R_\theta L$. These are the unity-PF, negligible-reactance form of Schneider Electric's voltage-drop equations.

Full-rating cable checks always use wallbox rated current, independently of the present vehicle limit and load management. The selected cable must meet the entered feeder drop budget, and the entered protection must satisfy $I_b\le I_n\le I_z$. The smallest listed section meeting voltage drop alone is shown separately. Its thermal suitability is not inferred from resistance.

DIN VDE 0100-722:2019-06, interpreted in DKE's 3 December 2025 FAQ, requires suitable additional RCD protection ≤30 mA per connection point. The concept shown is Type A with certified 6 mA DC disconnection (e.g. RDC-DD to IEC 62955), or Type B when that function is absent. An integrated DC sensor does not by itself replace an RCD. Coordinate upstream RCDs and follow manufacturer instructions.

Verification also checks the line-to-line drop independently as the magnitude of the difference of two phase-conductor drop phasors separated by 120°, and checks that feeder Joule loss equals the three-phase power associated with the in-phase voltage drop.

• All modelled wallboxes and vehicles are identical, three-phase and balanced, at approximately unity power factor; other loads are represented conservatively by current on the busiest phase. No household diversity factor is invented.
• Each wallbox has a separate final circuit of the same length and copper size. The number entered is the simultaneous group; include the nameplate ratings of all additional installed chargers under “other installed chargers”, even when idle.
• Resistive voltage drop and phase-conductor Joule loss only; negligible neutral current, cable reactance, harmonics and AC skin/proximity effects. Values are AC input at the distribution board, not DC battery power.
• Temperature rise 0–50 K corresponds to 20–70 °C copper. The default is 70 °C. Ambient temperature and grouping affect ampacity separately.
• The 3% remaining drop budget, 5 A reserve and 32 A corrected ampacity are illustrative design inputs, not standard limits or an ampacity determination. Re-enter corrected ampacity after changing cable or installation. A passing screen relies on that entered value.
• Dynamic allocation is an instantaneous equal-share calculation, not a daily energy forecast. No vehicle sequencing, automatic phase switching, PV surplus, battery storage, charging-time prediction or grid curtailment simulation is included.
• Core equations are derived from balanced power, Ohm's law and Joule heating; published sources support the application, component ratings and reference values.

Planning tool for new private balanced three-phase AC wallbox installations, nominally 400 V, 11 or 22 kW per point; copper class 2 conductors, listed sizes 1.5–35 mm², 20–70 °C. The simplified full-rating drop must remain at or below 10%; larger calculated drops block result cards and require a revised cable study. Longer or unusual routes require a complete impedance model. A zero available charging current means paused operation.

Germany: rules checked 25 October 2026. NAV §19 requires notification before commissioning every EV charging installation, not only above 3.6 kVA. Prior consent is required when total installed charger nameplate apparent power exceeds 12 kVA per electrical installation. This tool conservatively screens nameplate sum without treating a user-entered local cap as an exemption; agree any permanently restricted connection rating with the operator. DKE FAQ s1 page 3, question 5 also confirms notification and the 12 kVA threshold. Local operator technical connection conditions still apply.

For new private low-voltage wallboxes above 4.2 kW commissioned from 1 January 2024, §14a EnWG participation and grid-oriented controllability apply. The regulator describes a 4.2 kW minimum for direct control during a grid constraint; multiple-device EMS allocation has separate rules and is not calculated here. Local static/dynamic load management is a separate function. Older installations, exceptions, public charging and non-German rules require their own review.

Installation work and commissioning belong to a qualified electrician. Check against the standard in force. This screen does not establish compliance or select a final cable/protection system. Verify installation-method ampacity, ambient/grouping derating, continuous meter capacity, PE/neutral sizing, earthing, disconnection times, fault-loop impedance, short-circuit withstand, breaker curve/breaking capacity, RCD coordination and surge protection. No NEC 125% sizing rule or US installation approval is implied by the US unit display. Schematic and cable-candidate text retain nominal SI labels; numeric fields and charts use the catalog unit switch.