Safety & earthing
Earthing systems, protection, island-mode and how to identify your earthing system.
#10UK earthing systems explained — TT, TN-S, TN-C-S (PME), TN-C, IT
The overview hub for UK earthing systems: what TN-S, TN-C-S (PME), TT, TN-C and IT are, how they differ, and why your earthing system changes the whole V2L design.
Reviewed — public with Not-confirmed gates · Last reviewed 2026-06-14
#11How to identify your earthing system
An on-site identification guide: how to tell whether your supply is TN-C-S (PME), TN-S or TT by looking at the cut-out and main earth — and why you treat an apparent TN-S as TN-C-S unless the DNO confirms.
Reviewed — public with Not-confirmed gates · Last reviewed 2026-06-14
#12TN-C-S (PME) explained — and the open-PEN problem
How a TN-C-S (PME) supply works, why the combined PEN conductor creates the open-PEN hazard, and what that means for an EV connection under BS 7671 §722.411.4.1.
Reviewed — public with Not-confirmed gates · Last reviewed 2026-06-14
#13TN-S explained — the separate-earth supply, and what it means for V2L
What a TN-S earthing system is — a separate protective earth from the supply transformer, kept distinct from neutral throughout — and what it means for a V2L arrangement.
Reviewed — public with Not-confirmed gates · Last reviewed 2026-06-14
#14TT explained — and the TT-island method for outbuildings
What a TT earthing system is, why RCD protection and a low, stable electrode resistance are essential, and how a separate outbuilding is made TT to host a V2L island.
Reviewed — public with Not-confirmed gates · Last reviewed 2026-06-14
#15Floating vs bonded V2L outputs — the neutral-earth bond
Why many EV V2L outputs are floating, why that means no RCD protection until a neutral-earth bond is made, and why bonding the V2L neutral to earth is correct, not wrong.
Reviewed — public with Not-confirmed gates · Last reviewed 2026-06-14
#16Open PEN, PME and EVs — the Section 722 anchor
Why BS 7671 §722.411.4.1 restricts relying on a PME earth for an EV, the listed open-PEN protective measures, and how this drives the V2L earthing decision.
Reviewed — public with Not-confirmed gates · Last reviewed 2026-06-14
#17Island-mode earthing & neutral switching — Section 551
Why an islanded V2L source needs an independent means of earthing (BS 7671 §551.4.3.2.1), how neutral switching fits the changeover, and why the distributor's earth cannot be relied on alone in island mode.
Reviewed — public with Not-confirmed gates · Last reviewed 2026-06-14
#18RCD, RCBO and SPD selection for a V2L board
Choosing protective devices for a V2L board: why a plain Type AC RCD is not enough, when you need Type A/F/B and smooth DC detection, and how a V2L source's fault current differs from the grid.
Reviewed — public with Not-confirmed gates · Last reviewed 2026-06-14
#19Earthing & bonding fundamentals for V2L
The principle behind every V2L earthing decision: every source needs exactly one neutral-earth reference, the protective conductor stays continuous, and bonding is proven by test.
Reviewed — public with Not-confirmed gates · Last reviewed 2026-06-14