One 32A Mode 3 charge point, a common earthing mistake the calculator catches automatically, and how a Load Management System can roughly halve a 10-point site's feeder size.
| Charge point mode | Mode 3 (AC, with communication) |
| Rated current / voltage | 32 A, 400 V 3-phase |
| Circuit route length | 25 m, Method C, Cu/XLPE |
| Earthing system (for illustration) | TN-C-S (PME) |
| Site size | 10 charge points |
| Site feeder length | 40 m |
A TN-C-S supply carries a combined protective-and-neutral (PEN) conductor upstream of the property — IEC 60364-7-722 prohibits extending a PEN conductor into the final circuit feeding an EV charge point, because a lost PEN connection could otherwise put dangerous voltage onto the vehicle's exposed metalwork.
IEC 60364-7-722.311 requires a diversity factor of 1 (no reduction at all) when there is no LMS — every point must be assumed capable of drawing full rated current simultaneously.
| Check | Requirement | Actual | Status |
|---|---|---|---|
| Single charge point voltage drop | ≤ 5% | 3.81% | ✓ PASS |
| Earthing check (TN-C-S) | No PEN in final circuit | Warning triggered — conversion required | ✗ FAIL |
| 10-point feeder, no LMS | Support 320 A | 120 mm², 322 A capacity | ✓ PASS |
| 10-point feeder, with LMS (0.6) | Support 192 A | 70 mm², 229 A capacity | ✓ PASS |
Key insight: Diversity factors for EV sites are not a general convenience — IEC 60364-7-722.311 ties the right to apply any diversity below 1.0 directly to having a Load Management System in place. Without an LMS, every charge point must be assumed capable of running at full rated current at the same time, which is why the 'no LMS' feeder here has to support the full 320 A raw demand rather than any reduced figure.
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Open EV Charging calculator →In a TN-C-S (PME) system, the neutral and protective earth share a single PEN conductor for part of the network — if that PEN conductor breaks upstream, the property's earth terminal can float up to line voltage. On a normal socket circuit this is a recognized but generally low-frequency risk; on an EV charge point, a person may be standing on damp ground with one hand on a metal vehicle chassis connected to that same earth, which is exactly the scenario IEC 60364-7-722 singles out with mandatory extra protection (PEN conductor exclusion from the final circuit, open-PEN detection, or a local TT-style electrode).
It is not a fixed code value — IEC 60364-7-722 deliberately leaves the exact figure to the Load Management System's own real-time control strategy and the site design, which is why this calculator's note explicitly says to 'use your LMS/DSO-approved figure and verify it independently' rather than presenting 0.6 as a universal constant; a different LMS product or site agreement could justify a different figure entirely.