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Is an SPD as easy as 1, 2, 3? – Finder’s surge protection device range

A surge protection device (SPD) is designed not just for lightning strikes but also to protect valuable equipment from surges on the supply line. In the UK, the 18th Edition Wiring Regulations introduced requirements for protection against transient over-voltages of atmospheric origin or switching. In this article we will take a look at the different types of Finder SPDs and how they protect your components.


Do I need a surge protection device?

Changes to the 18th wiring regulations mean that surge protection devices (SPDs) have increased in importance. Now, a risk assessment is required to be carried out by an electrician to determine whether an SPD should be installed. If a risk assessment is not carried out, then an SPD must automatically be installed.

The risk assessment should take into account criteria such as:

  • result in serious injury to, or loss of, human life, or
  • result in interruption of public services and/or damage to cultural heritage,
  • result in interruption of commercial or industrial activity, or
  • affect a large number of co-located individuals.

What is the difference between a Type 1 and Type 2 surge protection device?

The Type 1 surge protection device (for example Type 7P.01 – Image 1) – is specifically recommended for service-sector and industrial buildings. It protects electrical installations against direct lightning strokes. It can discharge the back-current from lightning spreading from the earth conductor to the network conductors. Type 1 SPD is characterized by a 10/350 µs current wave.

The Type 2 surge protection device (for example Type 7P.23.9 – Image 2) is the main protection system for all low voltage electrical installations. Installed in each electrical switchboard, it prevents the spread of transient over-voltages in the electrical installations and protects the loads. Type 2 SPD is characterized by an 8/20 µs current wave.

What about Type 3?

The Type 3 surge protection device (for example Type 7P.37) is for local protection of sensitive loads. These SPDs have a limited protection capacity and are used in the vicinity of sensitive loads as a local supplement to the protection given by the Type 2 SPD. They must therefore only be installed as a supplement to Type 2 SPD and in the vicinity sensitive loads. Type 3 SPDs are characterised by a combination of voltage waves (1.2/50 μs) and current waves (8/20 μs).

Finder’s surge protection device range

Finder’s 7P Series consists of Type 1+2, Type 1, Type 2, and Type 3 surge arresters.

These devices include the following features (according to Type):

  • Surge arrester suitable for 230 V or 400 V networks
  • Single-phase systems or three-phase systems
  • Replaceable varistor module and encapsulated spark gap modules
  • Visual and remote signalling of varistor status
  • 35mm rail (EN 60715) mount

Type 1+2 are for the LPZ 0-1 boundary (where the supply enters the installation), Type 2 for the LPZ 1-2 boundary (main distribution panels within the installation) and Type 3 for the LPZ 2-3 boundary (local protection for individual sockets/items or cables).

Finder’s Type 1, 1+2, and 2 surge protection device range feature a remote signalling contact. This allows the module presence (all models) and status of the Varistor of the SPD device to be externally monitored. (Connector Type 07P.01 included.) The varistor modules have clear healthy/replace visual indication and feature reliable internal disconnection at end of life.

Type 3 SPD provides Local Protection for Sensitive Loads (Power sockets, data and signal lines).

Finder’s Type 7P.3X SPD  Type 3 Surge arrester (pages 17-18) for TT and TN-S systems (with Neutral) provides additional local protection in sockets or on DIN rails. The Types 7P.36/37 (page 18) provide a warning that a replacement is required, with Type 7P. providing an audible warning and Type 7P. a signalling contact.

Take a look at Finder’s full range of surge protection devices below. Contact our sales team to find out more information.