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What is a surge protection device (SPD)?

Surge protection devices (SPDs) are specifically designed to stop surges, also known as voltage spikes, from entering your electrical installation, by diverting the associated surge currents to earth. 

A surge is a very short, sharp increase in the voltage of the electrical system, which can lead to damage in electrical components. 

An SPD is a small component, installed in, or adjacent to your consumer unit alongside the other protective devices such as Circuit Breakers and RCDs. They can also be used locally for more sensitive equipment where required.

Surge Protection device
Surge Protection device

Examples of Surge Protection Devices 

What causes voltage spikes?

Normal mains supply waveform

Normal mains supply waveform

Transient over voltage waveform

Transient over voltage (surge) waveform

Voltage spikes, also known as surges or transients, are everyday occurrences. They can happen for many reasons, including power cuts, nearby lightning activity, electrical grid maintenance and local industry.

However, 80% of surges are actually generated inside our homes and come from such unsuspected sources as microwave ovens, laser printers, electrical appliances and even lights being switched on or off.

Most spikes are of low energy, and you may not be aware of them immediately, however they can cause irreparable damage to sensitive equipment if there is not an SPD installed to redirect the harmful voltage. 

An SPD will protect your installation from indirect lightning activity, which can cause surges from up to 2 miles away. However, unless your property has a lightning protection system installed, an SPD will not protect against direct lightning strikes to your property. 

Why should I consider an SPD?

Since the introduction of BS7671 Wiring Regulations:2018, the installation of surge protection devices has been recommended. 

Surges are not a new phenomenon, but due to technological advances, and a focus on energy efficiency, more and more equipment within your home contains sensitive electronic components, which can easily be damaged. Equipment such as smart TVs, computer equipment, phones, tablets and even household appliances such as washing machines, oven, hobs, fridge freezers, boiler control panels, alarms and LED lighting, all contain sensitive components that are vulnerable.

Basic diagram of surge protection

The basic concept of surge protection

Do I need to have an SPD installed?

BS7671 Wiring Regulations recommends that an SPD be installed in a domestic home if the value of the electrical equipment to be protected justifies the cost. 

The regulations do not have to be applied retrospectively to installations which were installed in accordance with earlier editions of the Wiring Regulations, however there are considerable benefits that should be considered.

Without surge protection, you may find that the warranty on your equipment is invalidated, or that it affects a home insurance claim. In fact, you may find that having an SPD fitted, will reduce your home insurance premium.

How much work is involved to fit surge protection to my electrical installation?

SPD installed in consumer unit

SPD installed in a consumer unit.

In most cases, Surge Protection Devices can be fitted in your existing consumer unit, if there is sufficient space. Subject to the age and condition of your consumer unit, it can be a relatively quick and inexpensive job. Alternatively, SPDs can also be mounted externally, in a separate enclosure.

If you are upgrading your existing consumer unit anyway, it is the ideal time to install a surge protection device (SPD). This way, any maintenance, additions or alterations in the future, will be likely to comply with BS7671 Wiring Regulations in terms of Surge Protection, future-proofing your installation.

How much maintenance do SPDs need?

SPDs require very little maintenance. Should a surge occur, it will send any excess voltage to earth and reset itself, without disrupting your supply. 

How long the device lasts will be dependent on the number and extent of the surges that it has to handle, however they are designed to last for many years.

Surge protection devices are equipped with an easy means of indication which will inform you once the device has reached the end of its life. To replace, it is usually just a case of replacing a cartridge. 

SPD label.jpg

Maintenance label fitted to consumer unit.

Please feel free to contact us to find out more about how surge protection devices can protect your home.

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