Surge protection device (SPD): Type 1, 2 or 3, and where to fit it?

A house without a lightning protection system usually gets a Type 2 SPD in the main distribution board. A house with lightning protection needs Type 1 or a combined Type 1+2 at the service position or main board. Type 3 is extra protection close to sensitive equipment (TV, computers, network gear), fitted within a few metres of it.

Surge protection device types 1, 2, 3: which one and where to install

For 230/400 V installations to IEC standards (Europe, UK and most of the world). North America uses different voltages, colours and rules: see the “Around the world” notes.

Diagram: main switch, SPD protection fuse, surge protector connected short and thick to the PE bar and earth — Connect the SPD to the earth bar with the shortest, thickest lead possible.

Which type

Type (IEC 61643-11)	Protects against	Where
Type 1 (Class I)	lightning current from a lightning protection system	service position or main board, when the house has lightning protection
Type 2 (Class II)	surges from the network and induced surges	main board: the standard for a house without lightning protection
Type 1+2 (combined)	both	main board of a house with lightning protection
Type 3 (Class III)	residual surges at the equipment	sub-board or socket near TV and IT equipment

Installation rules

Connect the SPD to the PE bar with the shortest, thickest lead possible. A total lead length of 0.5 m or less is the usual recommendation (IEC 60364-5-53); long leads ruin the protection.
The SPD has its own upstream protection (fuse or breaker) rated as the manufacturer specifies, unless the model has it built in.
It only works with good earthing. Without an earth electrode a surge has nowhere to go.
After a heavy storm check the status window: replace a spent cartridge.

Around the world:
• UK and Europe: the same Type 1, 2 and 3 (BS EN / IEC 61643). In the UK, surge protection is now routinely fitted in consumer units.
• USA: SPDs are listed under UL 1449, whose "Type 1/2/3" are defined by installation location, not by the same tests. Do not mix the two systems when buying.

Important: whether the building has lightning protection, the lead lengths and the SPD's protective device all come from the design. Installation in the main board and the earth test are done by a qualified person.