Surge protection has become an increasingly important consideration in modern electrical installations. As homes, commercial buildings and industrial environments rely more heavily on sensitive electronic equipment, protecting systems from transient over voltages and power surges is more critical than ever.
A power surge is a sudden spike in voltage within an electrical system. In the UK, the standard supply voltage is around 230V, but during a surge the voltage can briefly rise far above this level.
These spikes may last only milliseconds, but that is often enough to damage or degrade sensitive electrical equipment.
Common causes of electrical surges include:
Lightning strikes (even when not directly hitting a building)
Large industrial equipment starting up
Switching events within the electrical network
Power cuts and supply restoration
Over time, repeated surges can shorten the lifespan of electrical devices or cause sudden equipment failure.
This is where Surge Protection Devices (SPDs) play a vital role.
SPDs are designed to detect transient overvoltage and divert excess energy safely to earth, preventing damaging voltage from reaching connected equipment.
Understanding the Different Types of Surge Protection Device
Electrical installations can be protected using three different types of SPD, each designed to manage surges at different points within the system.
Type 1 SPD – Protection Against Direct Lightning Surges
Type 1 Surge Protection Devices are designed to handle extremely high energy surges caused by direct lightning strikes.
They are typically installed at the origin of the electrical installation and are most commonly used in:
Large commercial buildings
Industrial facilities
Buildings fitted with lightning protection systems
Type 1 devices provide the first line of defence against major surge events entering the installation.
Type 2 SPD – The Most Common Form of Surge Protection
Type 2 SPDs are the most widely used surge protection devices and are typically installed within the consumer unit or distribution board.
These devices protect the electrical installation against transient over-voltages coming through the supply network, helping prevent surge energy from travelling through circuits within the building.
For many installations, a Type 2 SPD provides the main level of surge protection.
However, protecting the installation itself does not always guarantee full protection for sensitive equipment.
Type 3 SPD – Critical Equipment Protection
While Type 2 SPDs clamp most of the surge energy at the consumer unit, smaller residual voltage spikes can still travel through the installation wiring.
This is where Type 3 Surge Protection Devices become essential.
Type 3 SPDs are installed close to the equipment they are protecting, providing what is often referred to as point-of-use surge protection.
Their role is to deal with the remaining transient voltage that can still reach sensitive electronics after upstream surge protection has already reduced the main surge.
By absorbing or diverting this remaining energy, Type 3 SPDs provide a final layer of protection directly at the equipment.
Typical Applications for Type 3 Surge Protection
Point-of-use surge protection is particularly beneficial where electrical equipment is sensitive, expensive or critical to operation.
Examples include:
Alarm and security systems
Medical equipment
IT and networking infrastructure
Industrial control panels
Building management systems
High-value electronic appliances
In these environments, even a small surge can lead to equipment damage, operational downtime, or costly repairs.
Installing a Type 3 SPD helps reduce these risks by protecting equipment at the point where it is most vulnerable.
The Importance of Layered Surge Protection
Electricians often refer to surge protection as a layered approach, where multiple types of SPD work together to provide comprehensive protection.
This layered protection typically includes:
Type 1 SPD – Installed at the supply to handle lightning surges
Type 2 SPD – Installed in the consumer unit to protect the installation
Type 3 SPD – Installed close to sensitive equipment to provide point-of-use protection
It is important to note that Type 3 SPDs should not be installed as standalone devices.
They are designed to handle lower energy surge events and should always be used in conjunction with upstream protection such as Type 2 or Type 1 devices.
When used together, these devices provide the most effective surge protection strategy for modern electrical installations.
Why Surge Protection Is Becoming More Important
Electrical installations today contain significantly more sensitive electronics than in the past.
Modern systems often include:
EV chargers
Smart home devices
LED lighting drivers
Security and alarm systems
Networking equipment
Connected appliances
These devices rely on delicate electronic components that are far more susceptible to voltage disturbances than traditional electrical equipment.
As a result, the need for effective surge protection and point-of-use protection is continuing to grow.
Don’t Stop at the Board
Installing a Type 2 SPD in the consumer unit is a critical step in protecting an electrical installation.
However, when it comes to protecting the devices that clients rely on most, surge protection should not stop at the board.
By adding a Type 3 SPD at the point of use, electricians can provide that final layer of protection that safeguards sensitive equipment and reduces the risk of costly failures.
In a world increasingly dependent on electronics, layered surge protection is becoming an essential part of a well-designed electrical installation.
If you’re working with our SPD’s or other electrical components – the team at CPN Cudis is here to help.
Browse CPN Cudis' range of SPD’s here!
Contact our technical experts for guidance on choosing the right SPD’s for your next project.