Do you install or manage electrical installations and wonder what the real difference is between a type 1 surge protector and a type 2 surge protector ? This choice is far from trivial: a poor selection exposes your equipment to destructive overvoltages, or even makes you liable in the event of an incident.
In this article, LPS France guides you step by step to understand the characteristics of each type, the applicable normative requirements and the selection criteria according to your installation.
What is a surge protector? Role and operating principle
A surge protector (or SPD – Surge Protective Device ) is a device that protects against overvoltages of atmospheric or switching origin. It dampens voltage spikes traveling on power lines before they reach sensitive equipment.
How does a surge protector work?
The surge arrester diverts excess transient currents to earth. When an overvoltage exceeds the protection level (Up), the active component of the surge arrester (MOV varistor, gas discharge tube, TVS diode, etc.) conducts and limits the residual voltage transmitted to the equipment.
Why distinguish between the different types of surge protectors?
The IEC 61643-11 (transposed into NF EN 61643-11) classifies surge arresters into three types according to their ability to dissipate lightning currents and their position in the installation. This classification directly determines when and where to install each device.
Type 1 surge protector: the first line of defense against direct lightning
Technical specifications
A Type 1 surge arrester (formerly known as Class I according to NF C 15-100) is designed to absorb direct lightning currents from a lightning strike hitting the electrical network or an installation equipped with a lightning rod. Its key characteristics are:
- Test waveform: 10/350 µs (shock wave simulating a direct lightning strike)
- Pulse current (Iimp): typically 12.5 kA to 50 kA depending on the model
- Main technology: gas or air bursts, resistant to very high energies
- Protection level (Up): generally greater than 2.5 kV
Where should a type 1 surge protector be installed?
Type 1 is installed at the head of the installation, that is to say:
- At the level of the main low-voltage switchboard (TGBT), upstream of the main circuit breaker
- Mandatory when the installation is equipped with a lightning protection system (lightning rod) according to standard IEC 62305-3 / NF EN 62305-3
- In Public Access Buildings (ERP), ICPE installations and industrial buildings subject to the decree of January 15, 2008
Regulatory obligations
The decree of January 15, 2008, mandates the installation of a type 1 surge protector in all classified installations (ICPE) equipped with a lightning rod. Standard NF C 15-100 (§ 443 and 534), aligned with the internationally applicable IEC 62305 standards, specifies the conditions under which type 1 is required in professional installations.
Type 2 surge arrester: protection against residual and switching overvoltages
Technical specifications
The Type 2 surge protector (formerly Class II) is the recommended basic protection in almost all residential and commercial installations. Its characteristics:
- Test waveform: 8/20 µs (wave simulating an induced overvoltage)
- Nominal discharge current (In): 5 kA to 20 kA depending on the model
- Maximum discharge current (Imax): up to 40 kA
- Main technology: MOV (Metal Oxide Varistor) varistors
- Protection level (Up): generally ≤ 1.5 kV
Where should a type 2 surge protector be installed?
Type 2 is installed:
- At the sub-distribution board or downstream of the main distribution board
- In all new housing since 2016 (NF C 15-100 amended)
- To protect sensitive equipment: IT, telecommunications, home automation, medical devices
- In addition to type 1 when the distance between the two devices exceeds 10 meters
Comparative table: type 1 vs type 2
| Criteria | Type 1 (Class I) | Type 2 (Class II) |
|---|---|---|
| test standard | IEC 61643-11 (10/350 µs) | IEC 61643-11 (8/20 µs) |
| Rated current | Iimp: 12.5 – 50 kA | In: 5 – 20 kA |
| Position in the installation | TGBT (upstream) | Subsidiary table (downstream) |
| Protection against | Direct lightning, lightning current | Induced overvoltages, maneuvers |
| Required with a lightning rod | Yes (IEC 62305-3) | Not mandatory at this level |
| Average cost | €150 – €600 (excluding installation) | €50–€200 (excluding installation) |
Can type 1 and type 2 be combined?
Coordination of protections
The IEC 61643-12 standard recommends cascaded protection: Type 1 at the head of the installation, Type 2 in the distribution network. This coordination is essential because:
- Type 1 absorbs large lightning currents but has a higher Up level
- Type 2 offers improved protection with a lower Up value, suitable for sensitive equipment
- There are combined type 1+2 (or T1+T2) devices that simplify installation and ensure internal coordination
The 10-meter rule
If the distance between type 1 and type 2 is less than 10 meters of cabling, they can work together without a decoupling device.
Beyond that, a separation inductance is needed to prevent the type 2 from handling currents for which it is not designed.
How to choose between type 1 and type 2?
Selection criteria
Here are the questions to ask yourself to choose the right surge protector:
- Is there a lightning rod on the building? → Type 1 required
- Is the installation classified as an ICPE (Installation Classified for Environmental Protection)? → Check the applicable decree
- Keraunic level (Ng) of your region? → The higher it is, the more robust the protection needs to be.
- What type of equipment needs protection? → Sensitive equipment: combine type 1 + type 2
- Overhead or underground network? → Overhead network: higher risk of inductive coupling
Mirods to avoid
- Installing a Type 2 switch alone on an installation with a lightning rod: it will be destroyed by the first direct lightning strike.
- Neglecting grounding: a surge protector cannot function correctly without an effective ground connection (resistance ≤ 50 Ω for standard protections)
- Forget about maintenance: surge protectors degrade over time and with each discharge. An annual inspection is recommended
Once your installation is compliant with IEC 62305, manage and plan its maintenance with LPS Manager , the lightning protection installation management platform.
Conclusion: Effective lightning protection depends on correct diagnosis
The difference between a type 1 and type 2 surge protector isn't simply a matter of power output; it's primarily about placement within your installation and the type of threat it's designed to protect against. Type 1 surge protectors are designed to handle direct lightning strikes on the front line, while type 2 protects equipment closer to your critical components.
In the vast majority of industrial and commercial facilities, the two types must coexist in a cascade.
Do you need a complete assessment of your lightning protection system or personalized advice to choose the right protection for your needs? LPS France , lightning protection specialists for over 30 years , are at your service. Contact our experts for a free assessment of your requirements.
