Built-in protection in the charger protects the charger itself and anything downstream. The external protection unit protects the supply cable between your consumer unit and the charger — a separate legal requirement under BS 7671 section 722. Think of it as two different jobs covering two different parts of the circuit.

The cable from your fuseboard to your charger needs its own dedicated circuit breaker and protection — that's what the upstream unit does.

Most UK homes use a PME (Protective Multiple Earth) supply, where the neutral and earth are combined in one cable. If that combined PEN conductor breaks, the earth in your property can rise to a dangerous voltage. With an EV plugged in, its chassis becomes connected to that voltage — creating a serious shock risk. Most modern chargers detect this automatically and disconnect. The Tesla Wall Connector Gen 3, GivEnergy charger, and CTEK Chargestorm Connected 3 do not — so an external PME unit is required.

Imagine the earth wire in your house accidentally going live. A PME unit monitors for this and cuts the charger off instantly before anyone can touch the car.

IP ratings describe how well an enclosure resists dust and water. IP40 (also marketed as IP30 in some product names) is for indoor or fully sheltered locations only — inside a garage or a dry utility room. IP65 is fully weatherproof and is required for any outdoor installation where the unit could be exposed to rain, spray, or condensation. If in doubt, IP65 is always the safer choice.

IP65 = suitable anywhere outdoors. IP40 = dry indoor locations only.

Smart EV chargers contain sensitive electronics that can be permanently damaged by transient voltage spikes — caused by nearby lightning strikes, grid switching, or other power quality events. BS 7671 section 443 recommends surge protection in most UK domestic and commercial installations. All EcoHarmony protection units include Type 2 surge protection as standard.

A surge protection device is like a lightning rod for your charger's circuit board. It absorbs voltage spikes before they can cause damage.

Yes. For installations with 2–6 single-phase chargers, or 2–3 three-phase chargers, a single 3-phase multi-charger PME unit is the correct solution. It provides PME fault detection, overcurrent protection, and surge protection for all circuits from a single upstream installation — suitable for driveways, apartment blocks, workplaces, and small car parks.

You don't need one box per charger — one multi-charger unit covers up to 6 single-phase or 3 three-phase chargers.

Yes. Tesla's own UK installation manual states that "additional requirements apply to UK properties fed from a TN-C-S supply" and that an external device providing PEN fault detection and isolation in accordance with BS 7671 is required. Unlike most chargers, the Tesla Wall Connector does not include built-in PME/PEN fault detection, making it one of the few mainstream chargers that always requires an external PME protection unit on a PME supply.

Tesla handles DC fault detection, but the PME earth risk needs a separate unit on most UK properties. It's not optional — it's in Tesla's own manual.