Simpson & Partners EV Chargers – Do They Need an Earth Rod?

⚡ Simpson & Partners · PME Compliance · BS 7671

Simpson & Partners EV Chargers — Do They Need an Earth Rod?

No. Simpson & Partners EV chargers include integrated PEN fault detection that automatically disconnects supply under fault conditions. No earth rod. No external WCED board. Just install, connect, and charge — with full BS 7671 compliance built in.

No earth rod · No external WCED board · Integrated PME compliance built in
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Direct Answer

Simpson & Partners EV chargers do not require an earth rod or an external WCED PME protection board on TN-C-S (PME) supplies. Each charger includes integrated PEN fault detection that continuously monitors supply voltage and automatically disconnects the charging circuit when a fault condition is detected — directly satisfying BS 7671 Regulation 722.411.4.1.

No earth rod required No external WCED board required Integrated PEN fault detection BS 7671 Reg 722.411.4.1 compliant Auto supply disconnection Fastest PME-compliant install path
🏠 Plain English — Why this matters for homeowners

Most EV chargers on the market need an extra protection box fitted before them — called a WCED board — because they can't handle the UK's most common type of electricity supply safely on their own. That adds cost, takes more installation time, and means more equipment.

Simpson & Partners chargers have the protection built in. The charger watches your electricity supply every second. If something goes wrong upstream, it cuts power automatically — before anything dangerous can happen to you, your car, or the charger. One less thing to buy. One less thing to install. Same level of protection.

Why Most EV Chargers Need External PME Protection

Around 80% of UK homes are on PME (TN-C-S) supplies — where neutral and earth are shared in the DNO cable network. If that shared cable fails upstream, it creates a fault that can make connected metalwork — including an EV charger casing and the vehicle body — dangerous to touch.

BS 7671 Section 722 requires protection against this scenario. Most EV charger manufacturers design to the minimum EVSE functionality — the charger delivers power and communicates with the vehicle, but it does not monitor its own supply for this specific upstream fault. So an external WCED board must be added upstream.

❌

Standard charger approach

Charger + separate WCED board upstream. More components, more wiring, more installation time, more to certify.

✅

Simpson & Partners approach

Protection built into the charger. Fewer components, simpler installation, lower total cost, same or better level of compliance.

How Simpson & Partners Integrated Protection Works

Each Simpson & Partners charger includes dedicated supply monitoring circuitry that continuously measures the voltage between L, N, and PE at the supply terminals — the same function a WCED board performs externally.

1

Continuous supply monitoring

The charger monitors the voltage relationship between L, N, and PE 24/7 — every second the charger is powered, whether or not it's actively charging a vehicle.

2

PEN fault detection

When a PEN conductor fails upstream, voltage falls outside the safe band — below ~207V or above ~253V. The charger detects this immediately.

3

Automatic supply disconnection

The charging circuit is isolated automatically — in milliseconds, before dangerous touch voltages can develop on the vehicle body, cable, or charger casing.

4

Automatic recovery

Charging does not resume until the supply voltage returns to safe levels. The charger self-monitors and reconnects automatically when the fault has cleared.

BS 7671 compliance: This process directly satisfies the Automatic Disconnection of Supply (ADS) requirement of BS 7671 Regulation 722.411.4.1 — without any external device. Active, continuous, and consistent regardless of soil conditions or installation environment.

What This Means for Installers — Real Differences

Installation Element Standard Charger on PME Simpson & Partners on PME
PME protection method External WCED board required upstream Built into charger — no external device
Earth rod needed? No (with WCED) or Yes (earth rod route) Never — integrated protection eliminates it
Components to procure Charger + WCED board + supply cable + RCBO Charger + supply cable + RCBO in CU
Typical install time 3–4 hours (WCED route) 1.5–2.5 hours
Groundwork required? No (WCED route) / Yes (earth rod) Never
Certification complexity Standard + WCED board documentation Standard — charger spec confirms compliance
Retrofit difficulty Moderate — new board required Replace charger only — minimal disruption

What Protection Is Still Required with Simpson & Partners

Integrated PME protection removes the need for a WCED board and earth rod. It doesn't remove all other protection requirements:

✅

Type A RCBO — still required

In the consumer unit feeding the charger. Provides circuit-level AC earth leakage (30mA) and overcurrent protection. Always required regardless of charger type.

✅

SPD — strongly recommended

BS 7671 Chapter 44 risk assessment typically recommends surge protection for outdoor EV installations. Can be installed at the consumer unit.

📋

DC leakage — check spec

Simpson & Partners chargers handle DC leakage internally. Confirm against the current installation specification for the specific model being installed.

Quick summary for the installation certificate: On a PME supply with a Simpson & Partners charger — Type A RCBO in consumer unit + Simpson & Partners integrated PME protection (in charger) + SPD (per risk assessment). Earthing arrangement: TN-C-S with integrated disconnection device.

The Simpson & Partners Range — Available from EcoHarmony

7kW Single-Phase — entry range

Basic Socket & Basic Tethered

Smart features, app control, OZEV compliant. Integrated PME protection. Socket or tethered (8m cable). Multiple colour options. Competitive pricing — call for volume rates.

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7kW Single-Phase — advanced features

Plus Socket & Plus Tethered

Load balancing, solar integration, Octopus smart tariff support, enhanced app. Integrated PME protection. All the smart features with the same clean installation.

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22kW Three-Phase & Freestanding

Three-Phase Range

High-power three-phase charging for faster charge times. Freestanding option for post or pedestal installations. Integrated PME protection across all models.

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⚡

Why installers and OEMs choose EcoHarmony for Simpson & Partners

We stock the complete Simpson & Partners range — all models, all finishes. We can advise on which model suits which installation scenario, and we offer competitive pricing with volume discounts for regular trade orders.

  • 🧠 Technical support — specification queries welcome
  • 💷 Trade pricing with volume discounts from 5+ units
  • 📦 OEM supply programmes available
  • 🚚 Same-day dispatch on stock lines

Simplify your next EV install

Built-in PME protection, no external board, no earth rod. The cleanest installation path for UK PME supplies.

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Frequently Asked Questions

Do Simpson & Partners EV chargers need an earth rod?
No. Simpson & Partners chargers include integrated PEN fault detection and automatically disconnect supply under fault conditions, satisfying BS 7671 Regulation 722.411.4.1 on TN-C-S supplies without an earth rod or any external protection device.
Do Simpson & Partners chargers need a WCED PME board?
No. The integrated PME protection within the charger replaces the function of an external WCED board. A Type A RCBO in the consumer unit is still required for circuit protection — but no separate WCED board is needed.
What regulation does Simpson & Partners integrated protection satisfy?
BS 7671 (18th Edition, Amendment 2) Section 722 Regulation 722.411.4.1 — the specific regulation requiring ADS protection against open PEN conductor conditions in EV charging installations on PME supplies.
How does Simpson & Partners compare to other charger brands for PME?
Most EV charger brands — Zappi, Ohme, Hypervolt, Pod Point, Wallbox, Easee — do not include integrated PME protection and require an external WCED board on TN-C-S supplies. Simpson & Partners is among the few UK-available brands that build PME protection in, resulting in simpler, faster, lower total cost installations.
Does integrated PME protection mean I don't need an RCBO?
The RCBO is still required in the consumer unit for circuit-level AC earth leakage and overcurrent protection. PME protection and RCBO address different fault types — both are needed. But the RCBO goes in your existing consumer unit — no additional board or enclosure required.
What happens if a Simpson & Partners charger detects a PME fault?
The charger automatically disconnects the charging circuit when voltage falls below ~207V or rises above ~253V. Charging does not resume until normal supply conditions return. This happens in milliseconds — before dangerous touch voltages can develop on the vehicle body or cable.
Are Simpson & Partners chargers OZEV approved?
Yes. Simpson & Partners chargers are OZEV approved and eligible for applicable government grants including the EV Chargepoint Grant for residential properties.
Do Simpson & Partners chargers work on TT supplies?
Yes. They work on all UK supply types. On TT supplies the PME detection function is not required (no shared PEN conductor) but the charger operates fully. Standard ADS and RCBO requirements under BS 7671 Section 722 still apply for TT installations.

Technical Glossary

Integrated PME
PEN fault detection built into the EV charger itself. Monitors supply voltage and automatically disconnects the charging circuit under fault conditions. Satisfies BS 7671 Reg 722.411.4.1 without any external device.
PEN Conductor
Combined Protective Earth and Neutral conductor in TN-C-S networks. Its open-circuit failure is the specific fault scenario Simpson & Partners integrated protection detects.
ADS
Automatic Disconnection of Supply — BS 7671 outcome requirement. Simpson & Partners integrated protection achieves ADS directly by automatically isolating the charging circuit on fault detection.
WCED Board
Wiring Centre with External Disconnection — PME protection board required for standard chargers on TN-C-S supplies. Not required for Simpson & Partners chargers.
Reg 722.411.4.1
The specific BS 7671 regulation requiring PEN fault mitigation in EV charging installations on PME supplies. Satisfied directly by Simpson & Partners integrated protection.
OZEV
Office for Zero Emission Vehicles — UK government body administering EV chargepoint grants. Simpson & Partners chargers are OZEV approved.
No earth rod. No board. Just Simpson & Partners. Complete range UK-stocked at EcoHarmony
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