Surge Protection Devices (SPDs)

What an SPD protects

Transient overvoltages can enter an installation via the distribution network (e.g. lightning-related events, switching on the grid) or be generated internally when large inductive loads switch. Modern homes contain increasing amounts of sensitive electronics: IT equipment, smart heating controls, induction hobs with electronics, audio-visual kit, LED drivers, and battery storage control gear. These devices are more vulnerable to voltage spikes than traditional resistive loads.

Surge Protection Devices (SPDs) limit the voltage that reaches downstream equipment by diverting surge current to earth. They are classified by type (e.g. Type 1, 2, 3) and must be positioned and coordinated correctly in the consumer unit or distribution system.

Tags: Safety · Regulations · Amendment 4 · Fire prevention (overvoltage stress can precede insulation failure)

Amendment 4 and domestic board upgrades

Industry practice has been moving for several years towards treating surge protection as standard on new and heavily modified domestic consumer units, subject to a documented risk assessment where the Regulations allow. BS 7671:2018+A4:2026 reinforces the expectation that designers and installers address transient overvoltages explicitly — particularly where equipment is vulnerable or where replacement cost and downtime are high.

For many consumer unit upgrades in Margate, Ramsgate and Broadstairs, we now specify an appropriate Type 1/2 or Type 2 SPD at the board (depending on supply and risk assessment), alongside RCBO protection and correct earthing/bonding. That gives a single point of defence for the whole installation, with supplementary Type 3 devices at sensitive sub-circuits only where justified.

EV chargers and compatibility

Electric vehicle charge points are both a significant load and a connection point for sophisticated power electronics. They should be installed with correct earthing, appropriate RCD/RCBO protection (often Type A or Type B RCD depending on the charger), and consideration of the installation’s overall surge withstand.

SPDs at the origin help protect not only household kit but also the charger's internal supply module from network-born transients. Coordination between SPD, MCB/RCBO ratings, and the charger manufacturer’s instructions is essential — particularly on PEN fault mitigation measures (e.g. where TN-C-S supplies and open PEN conductors are a consideration) which are governed separately from SPD selection but must be designed holistically.

If you are adding or upgrading an EV charger in Thanet, we integrate it into the wider board strategy rather than treating it as an isolated spur.

Maintenance and indicators

Many SPD modules incorporate visual indicators or require periodic inspection after major surge events. Your EICR or periodic inspection should record SPD presence and condition. If an indicator shows end-of-life, replace the module in line with the manufacturer’s instructions.