Type 1 SPDs handle partial lightning current (10/350 µs test waveform) at the service entrance; Type 2 SPDs handle induced and switching surges (8/20 µs) at distribution boards; Type 3 SPDs protect sensitive equipment close to the load. Most buildings need Type 2 at the main board; add Type 1, or a combined Type 1+2 such as the NU6-I+II, where an external lightning protection system or overhead lines expose the building.
Key facts
- SPD classes are defined in IEC 61643-11 (EN 61643-11 uses “Type 1 / 2 / 3”).
- Uc is the maximum continuous operating voltage; Up is the voltage protection level the SPD lets through. A low Up protects better; Uc must suit the system.
- An SPD does not replace an RCD or MCB — it works alongside them, usually with a backup protective device specified by the SPD datasheet.
Type 1, 2 and 3 compared
| Type 1 | Type 2 | Type 3 | |
|---|---|---|---|
| Test waveform | 10/350 µs (lightning current, Iimp) | 8/20 µs (In / Imax) | Combination wave (Uoc) |
| Protects against | Direct and partial lightning current | Induced surges and switching surges | Residual surges at the equipment |
| Typical location | Service entrance of buildings with an external lightning protection system or overhead supply | Main and sub-distribution boards | At or next to sensitive loads |
| CHINT example | NU6-I+II (combined Type 1+2) | NU6-II | — |
Choosing Uc for your earthing system
Uc must be chosen against the earthing system and the measured supply voltage. A Uc of 275 V is common on TN systems at 230/400 V; some earthing arrangements, such as IT, need a higher Uc (for example 440 V). On a legacy 127 V system the figures change again — size the SPD against the real system voltage, not the nameplate of the building. See our Saudi Arabia guide for the 127 V / 60 Hz case.
Selection checklist
- Earthing system (TN-S, TN-C-S, TT, IT) and nominal voltage.
- Is the building exposed — lightning rod, overhead line, tall structure? If yes, Type 1 or Type 1+2 at the entrance.
- Distance between SPD and protected equipment: add a Type 2 or Type 3 further downstream where the cable run is long.
- The backup fuse or MCB the datasheet requires, and its rating.
- Single-phase or three-phase, number of protected poles (for example 3P+N).
Browse the SPD, ATSE and isolator range or send your earthing system and board details for a quotation.
Frequently asked questions
Do I need an SPD if there is no lightning rod?
Often yes. Overhead supply lines and switching events cause surges even without direct lightning, which is what Type 2 devices address.
What does Type 1+2 mean?
A combined device tested to both the Type 1 (10/350 µs) and Type 2 (8/20 µs) requirements, so one unit covers service-entrance duty and board-level protection.
Is an SPD the same as a surge-protected power strip?
No. A board-level SPD is installed in the distribution board and protects the whole installation; a power strip is a Type 3 style device for individual equipment.
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Reviewed by the HAZAM technical team, October 2026. CHINT, DELIXI and TENGEN are trademarks of their respective owners. HAZAM is a first-tier authorised distributor of CHINT products; the authorisation certificate is available on request from our sales manager. Ratings and designations refer to published manufacturer documentation; the certificate for your exact ordering code governs.