Surge protection


What are electrical surges and why is it now a recommendation to install protection against them in the 18th edition of the wiring regulations?

Electrical surges, also known as transient over-voltages are voltage spikes caused by atmospheric conditions- lightning strikes or switching on main switch gear when there are many electrical loads connected. This produces transient voltage for short periods but can damage electronic components. Lightning strikes can produce voltages of 6,000 volts which can be imported into a building via power cables, telecommunications and signal lines.

In todays world where we rely on more and more sophisticated equipment to help us in our daily lives, LED lighting and inverters for Solar PV and wind turbines for example, it is more important now to protect the electronic components that we have in our homes and work places.

The recommendation for using Surge Protection Devices (SPD’s), was in the 17th Edition. However, rather than designers of electrical systems asking if there is a need to install SPD’s based on likelihood of transient voltages, it is now a requirement (Regulation 443.4) to provide surge protection where serious consequences caused by over-voltage could; 1) result in serious injury to, or loss of human life. 2) Result in interruption of public services and/or damage cultural heritage. 3)result in interruption of commercial or industrial activity 4) affect a large number of co-located individuals. For all other cases a risk assessment shall be performed. This regulation is now making it almost necessary to install SPD’s everywhere, except on domestic properties. However, it is worth considering installing SPD’s in the domestic market, particularly, if there is above average amounts of electronic equipment, such as home automation devices.

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Bundy's Electrical & Safety Testing Ltd.

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Registered office: 5 Beeston Pathway, Handbridge, Chester, CH4 7EG

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Registered in England And Wales.

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Bundy’s Electrical & Safety Testing Ltd.

Registered office:

5 Beeston Pathway, Handbridge, Chester,


Registered in England And Wales.Company Number 04738998