Professional note
Charger notifications, supply capacity applications, and formal design are project-specific. Use this page for orientation; rely on your electrician for certification.
Key takeaways
- PME (TN-C-S) is the standard Thanet supply — an open-PEN fault can raise dangerous voltages on vehicle metalwork without engineered protection.
- Earth electrode or O-PEN detection must be specified for PME-supplied EV charging — which to use depends on site, geology, DNO policy, and equipment.
- A CT clamp measuring real-time import is the correct way to implement load-shedding — paper diversity alone is not sufficient under current practice.
- The grid connection may need a DNO capacity application before installation — particularly relevant where solar or battery is already connected.
Earthing: PME (TN-C-S) versus earth rods (TT)
Most Thanet properties are on PME / TN-C-S: the distributor combines neutral and protective functions on the network, then the installation separates protective earth and neutral at the intake. EV charging introduces a long metallic path to a vehicle outdoors; if a PEN fault occurred on the network, touch voltages could theoretically rise on earthed metalwork. Designers therefore apply either:
- TT-style separation using a local earth electrode (rod or array) for the EV circuit or installation earth, with Ze measured to prove automatic disconnection; or
- Approved O-PEN / open-PEN detection built into or paired with the charge point, which monitors the supply and isolates the charger before dangerous conditions persist — sometimes avoiding a rod where product certification and BS 7671 permit.
The choice depends on site layout, geology, DNO policy, and equipment. Terraced streets with no front garden often favour O-PEN–capable hardware; rural or soft-ground sites may suit rods. There is no universal shortcut.
Load-shedding and the main fuse: why CT clamps matter
Your cut-out may be rated at, say, 60 A or 100 A. The EV charger might be 32 A; add an immersion, oven, and heat pump concurrently and the aggregate demand can exceed what the service fuse will tolerate continuously. Amendment 4-era practice expects evidence-based load management: not just diversity on paper, but dynamic control where overload is otherwise inevitable.
A current transformer (CT) clamp on the incoming tails (or other approved sensing) measures real-time import. The charge point or controller then throttles EV charge current so the house never demands more than the agreed headroom. That protects the main house fuse, avoids nuisance loss of supply, and demonstrates a competent design to inspectors. It is why “just fit a 32 A breaker” without a whole-installation study is no longer a professional answer on many sites.
Grid, DNO, and the bigger picture
The grid connection is finite. Your installer may need a supply capacity check or application to the DNO before or alongside install. Load management supports not only your fuse but also local network stability as EV uptake grows. Coordinated design with any solar, battery, or heat pump circuits keeps the single-line diagram honest.
Tags: EV Charging · Amendment 4 · Earthing · Renewables · Regulations
Full technical guide
For RCD types, bidirectional (V2H) notes, and worked context, see our Complete Guide to EV Home Charging and the EV charger installation service page.
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Get a quotationLast Updated: March 2026 — content reviewed against BS 7671:2018+A4:2026.