Standard explained
Surge Protection (SPD) Explained
A surge protective device (SPD) limits transient overvoltages from lightning or switching, protecting sensitive electrical and electronic equipment under BS 7671.
A surge protective device (SPD) protects an installation against transient overvoltages — brief, high-voltage spikes caused by lightning activity or switching events on the network. These spikes can damage sensitive electronic equipment and, in some cases, present a safety risk.
What SPDs do
An SPD diverts the surge energy safely to earth, clamping the voltage to a level the installation and connected equipment can withstand. They are commonly installed at the origin of the installation (the main board) and, where needed, closer to sensitive equipment.
When SPDs are required
BS 7671 introduced wider requirements for surge protection based on a risk assessment of the consequences of an overvoltage — considering factors such as the value and importance of equipment and the potential impact on services. In many commercial and institutional settings, fitting an SPD is now the expected outcome.
On an EICR
The absence of surge protection may be recorded, typically as a C3 improvement recommendation, depending on the installation and its use. Adding an SPD during a board upgrade is a straightforward way to protect valuable equipment — see distribution boards.
Related service
RCD, RCBO & SPD Upgrades
Improved protection through residual-current, overcurrent and surge protective devices.
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Standard explained
AFDDs (Arc Fault Detection Devices) Explained
An AFDD detects dangerous arcing faults in wiring — a common cause of electrical fires — and disconnects the circuit. BS 7671 recommends them for certain premises.
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BS 7671 Explained: The Wiring Regulations
BS 7671 — the IET Wiring Regulations — is the national standard for the safety of electrical installations in the UK, currently the 18th Edition.
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Cable Selection and Sizing Explained
Cable selection under BS 7671 balances current-carrying capacity, installation method, grouping, ambient temperature and voltage drop so conductors run safely.
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Distribution Boards and Consumer Units Explained
Distribution boards (and domestic consumer units) house the protective devices that control and protect each circuit — their condition is central to any EICR.
Learn moreThis article provides general guidance and distinguishes legislation, British Standards and good practice. It is not legal advice. Always confirm the specific duties applying to your property and tenure.