A Type 2 SPD is a distribution-level surge protective device used to limit transient overvoltages in low-voltage electrical systems. It is commonly installed in main distribution boards, sub-distribution boards, control panels, and secondary protection points.
Table of Contents
What Is a Type 2 SPD?
A Type 2 SPD is a surge protective device tested with an 8/20 μs discharge current waveform. In IEC terminology, it is commonly associated with Class II surge protection. Its main role is to reduce transient overvoltages to a safer level before they reach downstream circuits and equipment.
Type 2 SPDs are widely used because most buildings, industrial panels, machinery systems, and commercial electrical installations need protection against switching surges and indirect lightning effects at the distribution level.
Where Is a Type 2 SPD Installed?
A Type 2 SPD is normally installed at the distribution level of the electrical system. The exact position depends on the system design, the upstream protection stage, cable length, grounding quality, and local installation rules.
| Installation point | Typical use | Why Type 2 SPD is used |
|---|---|---|
| Main distribution board | Commercial buildings, workshops, factories | Limits surges entering or circulating through the main low-voltage distribution system. |
| Sub-distribution board | Branch circuits, floors, machine zones | Reduces residual surge voltage before it reaches downstream loads. |
| Industrial control panel | PLC cabinets, motor control panels, automation systems | Protects sensitive control components from switching and induced surges. |
| OEM electrical assembly | Distribution boxes, machinery panels, power cabinets | Adds integrated surge protection inside finished electrical equipment. |
When Should You Choose a Type 2 SPD?
Distribution protection
Choose Type 2 SPD for distribution boards and sub-panels where downstream circuits need protection from transient overvoltages.
Switching surge protection
Type 2 SPD is suitable for reducing surges caused by motors, transformers, HVAC equipment, contactors, and grid switching events.
Secondary protection
When a Type 1 or Type 1+2 SPD is installed upstream, Type 2 SPD can provide additional downstream protection.
Good use cases
- AC distribution boards
- Industrial control panels
- Commercial electrical cabinets
- Machinery power panels
- OEM low-voltage assemblies
Not enough by itself when
- The building has external lightning protection
- Partial lightning current may enter the installation
- The project requires Type 1 impulse current discharge
- The installation is exposed to severe lightning risk
- Local rules require Type 1 or Type 1+2 upstream protection
How to Select a Type 2 SPD
Type 2 SPD selection should be based on system voltage, protection mode, discharge current rating, voltage protection level, short-circuit withstand capability, installation position, and maintenance requirements.
| Selection factor | What to check | Why it matters |
|---|---|---|
| System voltage | Nominal voltage and maximum continuous operating voltage, Uc | The SPD must remain stable during normal operation and TOV conditions. |
| Protection mode | L-N, L-PE, N-PE, 1P, 2P, 3P, 3P+N, 4P | The protection mode must match the earthing system and panel wiring. |
| Discharge current | In and Imax based on 8/20 μs waveform | These ratings show the surge current duty the Type 2 SPD can handle. |
| Voltage protection level | Up value | Lower Up helps reduce residual overvoltage reaching downstream equipment. |
| Short-circuit rating | SCCR / ISCCR and backup protection requirement | The SPD must coordinate safely with the electrical system and protective device. |
| Maintenance | Pluggable module, visual indicator, remote signaling contact | These features make inspection and replacement easier in panels and OEM assemblies. |
Type 2 SPD Ratings Explained
A Type 2 SPD should not be selected only by its maximum current number. Buyers should check the full group of ratings because each parameter describes a different part of the protection performance.
Uc
Maximum continuous operating voltage. It must be suitable for the system voltage and expected voltage tolerance.
In
Nominal discharge current under the 8/20 μs waveform. It represents repeated discharge performance under defined test conditions.
Imax
Maximum discharge current under the 8/20 μs waveform. It indicates the peak discharge capacity for Type 2 duty.
Up
Voltage protection level. It shows the residual voltage level after the SPD operates under test conditions.
TOV
Temporary overvoltage withstand behavior. This is important for system safety and end-of-life performance.
Backup protection
Some installations require a fuse or breaker coordinated with the SPD according to manufacturer instructions.
Type 2 SPD for AC Distribution Boards
In AC distribution boards, Type 2 SPDs are usually installed in parallel with the power supply. They should be connected with short, straight conductors and a reliable grounding path to reduce residual voltage and improve protection performance.
| AC system | Common SPD configuration | Typical application |
|---|---|---|
| Single-phase AC | 1P+N or 2P Type 2 SPD | Residential boards, small commercial panels, single-phase equipment |
| Three-phase AC | 3P or 3P+N Type 2 SPD | Factories, machinery panels, power distribution cabinets |
| TT / TN systems | Configuration depends on earthing system | Electrical boards where correct N-PE or L-PE protection mode is required |
For DC solar systems, use DC-rated Type 2 SPDs selected according to PV string voltage and IEC 61643-31 requirements. Do not use an AC-only SPD on the DC side of a PV system.
Recommended LEEYEE Type 2 SPD Options
LEEYEE provides DIN rail Type 2 SPDs for distribution boards, control panels, and OEM electrical assemblies. The exact model should be selected according to system voltage, poles, protection mode, discharge current, and certification requirements.
LY1-C40/3(S)+1 Pluggable Multi-Pole SPD
A 3P+N Type 2 AC SPD for three-phase distribution boards and industrial panels.
View ProductType 2 DIN Rail SPD Series
Pluggable Type 2 surge protective devices for AC distribution boards, control cabinets, and OEM panel builders.
Request Model MatchInstallation Notes for Type 2 SPD
Correct installation is as important as correct model selection. A suitable Type 2 SPD can perform poorly if the connection length is too long, the grounding path is weak, or the backup protection is not coordinated.
Keep leads short
Long conductors increase residual voltage. Keep SPD wiring as short and straight as possible.
Check grounding
The SPD needs a low-impedance path to earth or equipotential bonding for effective surge diversion.
Use correct backup protection
Follow the manufacturer’s fuse or breaker coordination requirement for the selected SPD model.
Common Mistakes When Choosing Type 2 SPD
Mistake 1: Choosing only by Imax
Imax is important, but it is not the only rating. Uc, Up, In, TOV behavior, poles, and backup protection must also be checked.
Mistake 2: Using AC SPD on DC circuits
AC and DC SPDs are not interchangeable. DC systems, especially PV systems, need DC-rated SPDs.
Mistake 3: Ignoring upstream lightning risk
If lightning current may enter the system, Type 2 alone may not be enough. A Type 1 or Type 1+2 SPD may be required upstream.
Mistake 4: Poor wiring layout
Excessive cable length and poor grounding can reduce the real protection level even when the SPD rating looks correct.
Type 2 SPD FAQ
What is a Type 2 SPD used for?
A Type 2 SPD is used for secondary surge protection in distribution boards, sub-distribution boards, control panels, and low-voltage electrical systems. It limits induced lightning surges, switching surges, and residual surge energy.
Is Type 2 SPD the same as Class II SPD?
In IEC-based terminology, Type 2 SPD is commonly associated with Class II testing and the 8/20 μs discharge current waveform.
Can Type 2 SPD be installed without Type 1 SPD?
In many ordinary distribution systems, Type 2 SPD can be used as the main distribution-level SPD. However, if the installation has external lightning protection or significant lightning-current exposure, Type 1 or Type 1+2 protection may be required upstream.
Where should a Type 2 SPD be installed?
It is commonly installed in main or sub-distribution boards, close to the circuits being protected. The wiring should be short and properly grounded.
How do I choose the right Type 2 SPD?
Check the system voltage, Uc, In, Imax, Up, pole configuration, protection mode, earthing system, short-circuit rating, backup protection, and whether a pluggable or remote-signal design is needed.
Need Help Selecting a Type 2 SPD?
Send us your system voltage, pole configuration, installation position, and application. LEEYEE can help match a Type 2 SPD for distribution boards, control panels, and OEM electrical assemblies.
