Electrical Safety Knowledge Base | Wiring Protection Explained | EcoHarmony

Electrical Safety Knowledge Base

Everything you need to know about electrical protection devices, surge protection, and distribution equipment — written for UK installers and homeowners.

Modern electrical installations depend on a layered approach to safety. No single device provides complete protection — correct design requires understanding what each component does, when it's required, and how they work together. This knowledge base covers every major device category used in UK domestic and commercial installations, from standard RCBOs to specialist Type B RCDs, arc fault detection devices, surge protection, and fully assembled enclosures.

All guides are written to UK standards (BS 7671:2018, 18th Edition including Amendment 2) and link directly to the relevant products in the WCED range.

3 knowledge pillars covering all protection categories
20+ in-depth technical guides and explainers
BS 7671 18th Edition AMD2 — all guidance up to date
WCED all products available to buy directly
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Protection Devices

RCBOs, RCDs, MCBs, AFDDs and Type B devices — what they are, how they work, when each is required, and how to choose the right one for each circuit.

1
What is an RCBO? (vs MCB vs RCD) The difference between the three most common protection devices — and when each is the right choice.
2
RCBO types: A, B, AF — explained Type A vs Type B vs arc fault RCBO — what the classification means and which is required where.
3
What is a Type B RCD? Why EV charging needs it DC leakage detection explained — and why standard Type A RCDs aren't always sufficient for EV chargers.
4
Arc fault detection (AFDD) explained How AFDD devices detect fire-causing arc faults that MCBs and RCDs cannot — and when they're mandatory.
5
RCD trip sensitivity: 30mA vs 100mA vs 300mA When to use each sensitivity rating — personal protection, fire protection, and selective discrimination.
6
Time delay RCDs — when and why S-type time delay RCDs for discrimination and upstream protection — what they are and how to apply them.
7
4-pole vs 2-pole RCDs for 3-phase When a 4-pole RCD is required and when a 2-pole is sufficient — guidance for three-phase installations.
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RCBOs, Type B RCDs, AFDDs, time delay RCDs and more — all in stock with next working day dispatch.

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Surge Protection

Type 1, Type 2, and combined SPDs — when they're required under the 18th Edition, how they work, and which to specify for EV, solar, and heat pump installations.

1
Type 1 vs Type 2 vs Type 1+2 SPD The three SPD categories explained — location, impulse ratings, and which is appropriate for each installation.
2
Do I need surge protection? (18th Edition) When SPDs are required under BS 7671 Amendment 2 — risk assessment, building types, and practical guidance.
3
SPD for EV chargers Why EV supply circuits benefit from surge protection and how to integrate SPDs into EV distribution boards.
4
SPD for solar and heat pumps Surge protection for PV arrays and heat pump installations — AC and DC protection requirements explained.
5
DC surge protection (1000V) High-voltage DC SPDs for solar string protection — how they differ from AC devices and where they're installed.
6
How to install an SPD — installer guide Connection methods, cable lengths, earthing requirements, and common installation mistakes to avoid.
7
SPD kA rating explained (40kA) What the impulse current rating means, how to read SPD specs, and why 40kA is the standard for most installs.
Shop WCED surge protection devices

Type 2 SPDs, Type 1+2 combined units, DC solar protection, and SPD cable kits — all from the WCED range.

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Enclosures & Assemblies

Consumer units, distribution boards, IP-rated enclosures, modular contactors, and specialist assemblies for EV, heat pump, and solar installations.

1
Fully assembled consumer units — why use them Pre-wired WCED boards vs field-assembled units — time savings, compliance confidence, and what's included.
2
IP40 vs IP65 enclosures explained When a standard IP40 metal enclosure is sufficient and when IP65 weatherproof protection is required.
3
Metal vs plastic enclosures The practical differences between metal IP40 and plastic IP65 enclosures — fire ratings, fixing, and application.
4
TPN 3-phase distribution boards explained Three-phase neutral (TPN) boards for 11–22kW EV charging, commercial supplies, and multi-circuit installations.
5
Modular contactors — what they do DIN-rail contactors for load switching, timer control, and EV charging management — how they work and when to use them.
6
Heat pump protection units B-type HP RCDs and dedicated heat pump enclosures — what protection is required for heat pump installations.
7
Solar combiner boxes explained PV string combiner boxes with DC surge protection — what they do, where they're installed, and which to choose.
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Metal and plastic enclosures, fully assembled consumer units, TPN boards, contactors, and specialist EV and solar assemblies.

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Common questions about electrical protection

What is the difference between an MCB, RCD, and RCBO?

An MCB (Miniature Circuit Breaker) protects against overloads and short circuits only. An RCD (Residual Current Device) detects earth leakage but offers no overcurrent protection. An RCBO combines both in a single module — it is now the standard for individual circuit protection in UK installations. See our full guide: What is an RCBO?

When is surge protection required under the 18th Edition?

BS 7671:2018 Amendment 2 requires a risk assessment for all new installations and recommends SPDs where the consequences of a surge event would be unacceptable. They are strongly recommended (and increasingly required by building regulations and insurers) for all new builds, consumer unit replacements, and installations supplying EV chargers, solar inverters, or heat pumps. See: Do I need surge protection?

What type of RCD does an EV charger need?

Most Mode 3 EV chargers that include their own internal DC leakage monitoring require at minimum a Type A RCD. Some 3-phase EV chargers without integrated DC protection require a Type B RCD. Always check the charger manufacturer's documentation. See: What is a Type B RCD?

Do I need an AFDD in my consumer unit?

Since March 2022, AFDDs are mandatory under BS 7671 Amendment 2 for socket circuits ≤32A in HMOs, care homes, higher-risk residential buildings over 18m, and purpose-built student accommodation. They are strongly recommended for all other domestic and commercial installations. See: Arc fault detection explained

What is the difference between IP40 and IP65?

IP40 means the enclosure is protected against solid objects over 1mm but offers no water protection — suitable for indoor use in dry conditions. IP65 means the enclosure is fully dust-tight and protected against water jets — required for outdoor installations or anywhere moisture may be present. See: IP40 vs IP65 explained

EV Charging Knowledge Base

Related guides covering PME protection, BS 7671 compliance, and EV charger selection for UK installers and homeowners.

Electrical Protection Devices ExplainedRCBO, RCD, MCB, surge protection and contactors — the complete overview. PME vs RCD vs RCBO vs RDC-DDEV charging protection — what each device does and why all are needed. Do I Need an Earth Rod?Installer decision guide for PME vs earth rod — with supply type flowchart. What is PME in EV Charging?TN-C-S supply explained — how PME works and why EV charging needs extra protection. Fully Assembled Consumer UnitsWhy pre-wired WCED boards save time and reduce installation errors. Find the Right EV ChargerBuyer guide for UK homeowners and installers — matching charger to supply type.
Browse the full WCED electrical protection range
Shop WCED products Datasheets