Fully Assembled WCED Consumer Units for EV Charging — Explained

📦 WCED Boards · BS 7671 · Installer Ready

Fully Assembled WCED Consumer Units for EV Charging — Explained

A fully assembled WCED board puts every required protection layer for EV charging on a PME supply into one pre-wired, pre-tested, IP65-rated unit. No component sourcing. No on-site assembly. Just install, connect, and sign off.

PME protection + RCBO + SPD · Pre-assembled · IP65 rated · Works with any charger brand
🧠Expert technical advice since 2012 💷Competitive trade prices 📦Volume & OEM discounts 🚚Fast UK dispatch
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Direct Answer

A fully assembled WCED (Wiring Centre with External Disconnection) consumer unit is a pre-built distribution board containing all the protection devices required for EV charging on a UK PME supply — PME fault monitoring, RCBO, and SPD — in one tested unit. It replaces the need for an earth rod, eliminates on-site component selection, and significantly reduces installation time.

PME protection + RCBO + SPD included No earth rod required Works with any charger brand Pre-assembled and tested IP65 weatherproof enclosure Single and three-phase options
🏠 Plain English — What is a WCED board and do I need one?

If you're having a standard EV charger installed (any brand that isn't Simpson & Partners), your installer needs to add a protection box somewhere between your main supply and the charger. That box is the WCED board.

Instead of sourcing three separate devices — a PME monitor, a safety switch, and a surge protector — and wiring them together on-site, the WCED board has everything already built in and tested. Your installer bolts it on the wall, wires it up, and the job is done. Faster, cleaner, and with less room for error.

If you have a Simpson & Partners charger, the board is built into the charger itself — you don't need a separate WCED board at all.

What's Inside a Fully Assembled WCED Board

Every EcoHarmony WCED board contains all required protection layers for EV charging on a PME supply in a single pre-tested unit:

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PME Protection Module

Continuously monitors supply voltage between L, N, and PE. Automatically disconnects the EV circuit when voltage falls outside 207–253V — the signature of a PEN fault condition upstream. This is the core function that satisfies BS 7671 Reg 722.411.4.1.

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Type A RCBO

Residual Current Breaker with Overcurrent — provides AC earth leakage protection (30mA) and overcurrent / short circuit protection for the EV charging circuit. Minimum standard under BS 7671 Section 722 for all EV installations.

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Type 2 SPD

Surge Protection Device — protects the charger and vehicle electronics against transient voltage spikes from lightning strikes and switching events. Recommended by BS 7671 Chapter 44 for all outdoor EV installations.

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IP65 Weatherproof Enclosure

Sealed against dust and water jets. Suitable for external installation in all UK weather conditions. All components pre-wired to manufacturer specification and tested as a complete system before dispatch.

Why this matters: On-site assembly of individual components introduces risk — wrong device selection, wiring errors, missing components. A pre-assembled, tested board eliminates all of this. What arrives is what installs, and what installs is what's been tested to work together.

Traditional Build vs Fully Assembled WCED — Installation Comparison

Factor Traditional On-Site Build Fully Assembled WCED Board
Component sourcing PME device, RCBO, SPD all sourced separately All included in one unit
On-site assembly time 30–60 mins component wiring + testing Pre-assembled — wiring connections only
Risk of component mismatch Present — devices must be compatible Eliminated — pre-tested as a system
Enclosure required? Must source and mount separately IP65 enclosure included
Typical total install time ~3–4 hours including assembly ~45–60 minutes wiring only
Commissioning documentation Individual device records Single board commissioning record
Earth rod needed? Only if no PME device — else No No — PME module handles it

The Protection Stack — How Each Component Works Together

The three protection layers inside a WCED board address three completely separate fault types. They're not redundant — each is essential:

PME module — what it does and when it acts

The PME module monitors the supply voltage relationship between L, N, and PE at the board's supply terminals. Under normal operation it does nothing — the charger runs normally through it. When a PEN conductor fails upstream on the TN-C-S network, the voltage profile changes: it typically falls below 207V or rises above 253V. The PME module detects this in milliseconds and disconnects the output to the EV charger — before the installation earth can rise to dangerous voltage levels.

This is the function that satisfies BS 7671 Regulation 722.411.4.1 and eliminates the need for an earth rod.

RCBO — circuit-level leakage and overcurrent protection

The Type A RCBO monitors current balance between live and neutral within the EV charging circuit. If current imbalance is detected (indicating earth leakage) at 30mA, it trips. If current exceeds the rated level (overload) or there is a short circuit, it also trips.

This is a completely separate protection function from the PME module — the RCBO monitors within-circuit faults; the PME module monitors upstream supply faults. Both are required; neither replaces the other.

SPD — transient overvoltage protection

The Type 2 Surge Protection Device provides transient voltage clamping — absorbing brief voltage spikes caused by lightning strikes on overhead lines, switching events in the DNO network, or other transient disturbances. Without an SPD, these spikes can damage the charger's electronics or the vehicle's onboard charging system.

BS 7671 Chapter 44 requires a risk assessment for surge protection on all new installations. For most outdoor EV installations on UK networks, the risk assessment result is positive — an SPD is recommended. Including it in the WCED board means this requirement is met without an additional device.

What about RDC-DD (DC leakage detection)?

RDC-DD detects smooth DC leakage from EV charger electronics that can blind a Type A RCD. Whether an RDC-DD is required depends on the specific EV charger — some chargers handle DC leakage internally; others specify a Type B RCBO or external RDC-DD.

Always check the EV charger manufacturer's installation manual for their specific requirement. If an RDC-DD is needed, it can be added upstream of the WCED board or at the consumer unit, or a Type B RCBO can replace the Type A RCBO in the board configuration.

Understanding RCBO, RCD, and MCB — The Building Blocks

WCED boards are built around these core protection components. Here's what each one does:

What is an RCBO?

An RCBO (Residual Current Breaker with Overcurrent) combines two functions in one device: earth leakage detection (like an RCD) and overcurrent/short circuit protection (like an MCB). For EV charging circuits, this is the preferred single-device solution — it protects against circuit faults without causing a whole-board trip.

RCBO: Type A vs Type B — which do you need?

Type A RCBO: Detects AC earth leakage and pulsating DC leakage. Minimum standard for most EV charging circuits. Used in standard WCED board configurations.

Type B RCBO: Also detects smooth DC leakage in addition to AC and pulsating DC. Required when the EV charger's installation spec specifies it — eliminates the need for a separate RDC-DD. Can be specified as an alternative in WCED boards.

Always check your charger manufacturer's installation manual for the required RCBO type.

Why not a standard RCD + MCB?

A split-load consumer unit with a shared RCD protecting multiple circuits is cheaper upfront but creates "nuisance tripping" — a leakage fault on the EV circuit trips protection for other circuits too. An RCBO provides per-circuit protection: only the affected circuit disconnects.

For EV charging: RCBO is always the recommended approach — dedicated per-circuit protection, no interaction with other loads, simpler certification.

Where the WCED Board Fits in a UK EV Installation

1

Supply feed from main consumer unit

A dedicated circuit runs from the main consumer unit (or distribution board) to the WCED board. Typically 32A or 40A for 7kW single-phase. The WCED board's own RCBO protects this circuit — no additional device needed at the consumer unit for the EV supply.

2

WCED board — mounted near the charger

Typically within 1–2m of the charger, externally mounted in the IP65 enclosure. All power to the charger passes through the board. The board monitors supply continuously and provides all required protection layers. Often mounted to the same wall bracket as the charger.

3

EV charger connected downstream

Any standard EV charger connects to the WCED board's output. No changes to the charger configuration. Compatible with Zappi, Ohme, Hypervolt, Pod Point, Wallbox, Easee, and all other standard charger brands.

4

Commission and certify

Test supply voltage at the board input, verify RCBO operation, confirm PME disconnection behaviour per device documentation. Record on installation certificate as TN-C-S with external disconnection device (WCED). Board commissioning record documents the protection system.

WCED Boards Available from EcoHarmony

Domestic — single phase (7kW)

Single-Phase WCED PME Board

PME protection + Type A RCBO + Type 2 SPD. Fully assembled, IP65, pre-tested. Compatible with any standard EV charger. UK-stocked. Competitive trade pricing — volume discounts available from 5+ units.

View Single-Phase Boards →
Commercial / 22kW — three phase

Three-Phase WCED PME Board

Three-phase PME protection + three-phase RCBOs + SPD. For 22kW EV charging and commercial installations on PME supplies. Fully assembled. Call for volume pricing and supply terms.

View Three-Phase Boards →
Alternative — no board required

Simpson & Partners Chargers

If the installation allows charger selection, Simpson & Partners chargers include integrated PME protection — no external WCED board needed. Often the fastest total installation path.

View Charger Range →
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Why installers and OEMs buy WCED boards from EcoHarmony

We've been specifying and supplying electrical protection equipment for EV charging since the market was young. Our WCED boards are UK-stocked and ready to go — no waiting for components, no on-site assembly, no spec uncertainty.

  • 🧠 Technical support on board selection and specification
  • 💷 Trade pricing — volume discounts from 5+ units
  • 📦 OEM supply programmes for integrators and electrical wholesalers
  • 🚚 Same-day dispatch on stock lines

Ready to simplify your EV install?

Fully assembled WCED boards — all protection layers, one unit, no assembly required. UK stock, fast dispatch.

Single-Phase WCED Boards Three-Phase Boards

Frequently Asked Questions

What is a fully assembled consumer unit for EV charging?
A pre-built distribution board containing all required protection devices for EV charging on a PME supply — PME fault monitoring, RCBO, and SPD — in a single tested, IP65-rated unit. It installs between the main consumer unit and the EV charger, eliminating the need for an earth rod and on-site component assembly.
What does WCED stand for?
Wiring Centre with External Disconnection — a distribution board that includes supply-side disconnection capability triggered by PME fault detection. The board provides a central protection point for the EV charging circuit with automatic isolation on PEN fault conditions.
What's the difference between a WCED board and a standard consumer unit?
A standard consumer unit provides overcurrent protection (MCBs or RCBOs) and RCD protection for household circuits. A WCED board adds PME-specific voltage monitoring and automatic supply disconnection on PEN fault detection — a function standard consumer units do not include. WCED boards also typically include an SPD as standard.
Do I need a WCED board if I have a Simpson & Partners charger?
No. Simpson & Partners chargers include integrated PME protection that directly satisfies BS 7671 Reg 722.411.4.1. An external WCED board is not needed. A Type A RCBO in the main consumer unit is still required for circuit protection.
What charger brands work with WCED boards?
All standard EV charger brands — Zappi, Ohme, Hypervolt, Pod Point, Wallbox, Easee, and any other EVSE. The WCED board sits upstream of the charger and is completely independent of the charger's brand and configuration.
Do I still need an earth rod with a WCED board?
No. The WCED board's PME protection module handles the upstream fault detection and automatic disconnection that an earth rod was historically used to partially address. No earth rod, no Ra testing, no groundwork.
What is an RCBO and why is it better than a separate RCD + MCB?
An RCBO combines RCD (earth leakage) and MCB (overcurrent) protection in one single-circuit device. Unlike a shared RCD protecting multiple circuits, an RCBO provides per-circuit protection — only the affected circuit trips on a fault, not the whole board. For EV charging this avoids nuisance tripping of other circuits and simplifies fault-finding.
Does a WCED board include surge protection?
Yes — EcoHarmony WCED boards include an integrated Type 2 Surge Protection Device (SPD) as standard. BS 7671 Chapter 44 requires a surge protection risk assessment, and for most outdoor EV installations an SPD is recommended. Having it in the board means this requirement is met without sourcing or installing a separate device.
How do I know if I need a single-phase or three-phase WCED board?
A single-phase WCED board is used for domestic 7kW EV charging on a standard single-phase supply. A three-phase WCED board is used for 22kW EV charging, commercial installations, or any installation on a three-phase PME supply. If unsure, confirm with your DNO and the charger manufacturer's specification.

Technical Glossary

WCED Board
Wiring Centre with External Disconnection — pre-assembled distribution board with PME fault detection, RCBO, and SPD for EV charging on TN-C-S supplies. Supplied fully assembled and tested by EcoHarmony.
PME Protection
Voltage monitoring and automatic supply isolation on detection of upstream PEN conductor failure on TN-C-S networks. The core function of the WCED board. Satisfies BS 7671 Reg 722.411.4.1.
RCBO
Residual Current Breaker with Overcurrent — combines RCD (30mA earth leakage) and MCB (overcurrent/short circuit) protection in one device. Type A standard; Type B for smooth DC detection.
SPD
Surge Protection Device — Type 2 transient overvoltage protection. Protects against lightning and switching voltage spikes. Included in all EcoHarmony WCED boards.
RDC-DD
Residual DC Detection Device — detects smooth DC leakage from EV charger electronics. Required when specified by the charger manufacturer. Can be added upstream of the WCED board if needed.
IP65
Ingress Protection rating — dust-tight and protected against water jets from any direction. Suitable for external mounting in all UK weather conditions.
Section 722
Part of BS 7671 (18th Edition) specifically governing EV charging installations — earthing, protection, and PME supply requirements. WCED boards are designed to satisfy all Section 722 requirements for PME supplies.
PEN Conductor
Combined Protective Earth and Neutral conductor in TN-C-S networks. Its failure is the upstream fault that WCED board PME protection detects and responds to.
Fully assembled WCED boards — UK stock All protection layers pre-built and tested
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