Type 1 vs Type 2 vs Type 3 SPD: What’s the Difference?
Modern buildings depend on electrical and electronic equipment every day. Computers, televisions, air conditioners, smart appliances and control systems are all sensitive to electrical disturbances.
A sudden increase in voltage can damage this equipment. This is why surge protection is an important part of a well-designed electrical installation.
But which surge protection device should you use?
You may have heard of Type 1, Type 2 and Type 3 SPDs. Although all three are designed for surge protection, they serve different roles.
In this guide, we explain the difference between Type 1 vs Type 2 vs Type 3 SPD, where each type is generally used, and what to consider before choosing one.
What Is a Surge Protection Device?
A Surge Protection Device (SPD) is designed to limit transient overvoltage and divert surge current.
Transient overvoltages can result from lightning-related events or switching operations in an electrical system. An SPD helps limit the voltage that reaches connected equipment.
In simple terms, an SPD acts as part of the electrical system’s defence against sudden voltage surges.
However, not every SPD is designed for the same location or application.
This is where Type 1, Type 2 and Type 3 SPDs come in.
What Are Type 1, Type 2 and Type 3 SPDs?
Type 1, Type 2 and Type 3 SPDs are used at different stages of an electrical installation.
A simple way to understand them is:
- Type 1 SPD: First stage of surge protection
- Type 2 SPD: Distribution-level surge protection
- Type 3 SPD: Additional protection near sensitive equipment
The exact arrangement depends on the building, electrical system and protection requirements.
What Is a Type 1 SPD?
A Type 1 SPD is generally used at the incoming side of an electrical installation.
It is designed for installations where protection against high-energy surge currents is required.
For example, Type 1 protection can be relevant to buildings with an external lightning protection system.
Type 1 SPDs are commonly associated with the first stage of surge protection. They can help manage high-energy surge currents before they travel further into the installation.
Where Is a Type 1 SPD Used?
A Type 1 SPD may be considered at:
- The incoming electrical supply
- The main distribution area
- Buildings with lightning protection systems
- Commercial installations
- Industrial installations
The exact location should be determined by the electrical design.
What Is a Type 2 SPD?
A Type 2 SPD is commonly installed in distribution boards.
It provides another level of protection against transient overvoltages within the electrical installation.
Type 2 SPDs are widely used in residential, commercial and industrial applications, depending on the installation requirements.
Where Is a Type 2 SPD Used?
Typical locations can include:
- Main distribution boards
- Sub-distribution boards
- Commercial electrical panels
- Residential distribution boards
- Industrial electrical installations
Type 2 protection can therefore be an important part of an installation’s overall surge protection strategy.
What Is a Type 3 SPD?
A Type 3 SPD is generally used closer to sensitive electrical or electronic equipment.
It provides additional protection after upstream surge protection has already been provided.
For example, Type 3 protection may be considered near equipment such as:
- Computers
- Televisions
- Networking equipment
- Electronic control systems
- Sensitive appliances
Type 3 SPDs have lower discharge capacity than Type 1 and Type 2 devices. Therefore, they are generally used as an additional stage of protection rather than as the only SPD in an installation.
Type 1 vs Type 2 vs Type 3 SPD
The easiest way to compare the three types is to look at their typical position in the electrical installation.
| SPD Type | Typical Application | Main Role |
|---|---|---|
| Type 1 | Incoming supply | Handles high-energy surge currents |
| Type 2 | Distribution board | Provides installation-level surge protection |
| Type 3 | Near sensitive equipment | Provides additional local protection |
These roles can work together as part of a coordinated surge protection system.
However, the exact arrangement should be based on the electrical installation design and applicable requirements.
Do You Need All Three Types?
Not every installation will require all three types.
The correct protection arrangement depends on several factors, such as:
- Building type
- Electrical system
- Lightning exposure
- Existing lightning protection
- Connected equipment
- Installation design
- Applicable standards
For this reason, you should not select an SPD simply because it is labelled Type 1, Type 2 or Type 3.
Instead, the complete electrical installation should be considered.
Can Type 3 SPD Be Used Alone?
Generally, Type 3 protection is intended to complement upstream surge protection.
A Type 3 SPD is designed for protection close to sensitive equipment. It has a lower discharge capacity than upstream SPD types.
Therefore, using a Type 3 device as the only layer of surge protection may not provide the protection required for the entire installation.
A coordinated arrangement can provide protection at different points in the electrical system.
How Do You Choose the Right SPD?
Choosing an SPD involves more than selecting Type 1, Type 2 or Type 3.
Other specifications also matter.
Schneider Electric recommends considering characteristics such as Voltage Protection Level (Up), Nominal Discharge Current (In), Maximum Discharge Current (Imax) and the appropriate SPD type.
Before selecting an SPD, consider:
1. System Voltage
The SPD must be suitable for the electrical system where it will be installed.
2. SPD Type
Choose the appropriate type based on the installation and required level of protection.
3. Discharge Current
Check the relevant discharge-current ratings for the application.
4. Voltage Protection Level
The voltage protection level is another important specification when evaluating an SPD.
5. Backup Protection
The SPD and its associated protective device must be properly coordinated.
Manufacturers provide coordination information for their products.
6. Installation Requirements
The wiring, earthing and installation method also matter.
For example, Schneider Electric notes that SPD connection length can affect performance because of the inductance of the conductors.
Why Is Proper SPD Installation Important?
Choosing the correct SPD is only one part of surge protection.
Installation also matters.
The SPD needs suitable connections to the electrical system and protective earth. The associated protective device must also be correctly coordinated.
For this reason, SPD installation should be carried out according to the manufacturer’s instructions and the applicable electrical requirements.
A qualified electrical professional should assess the installation before selecting and fitting protection equipment.
Type 1 vs Type 2 vs Type 3 SPD: Quick Summary
Here is the simple version:
Type 1 SPD
Used as the first stage of protection at the incoming side of an installation.
Type 2 SPD
Used mainly at distribution boards to provide protection within the installation.
Type 3 SPD
Used closer to sensitive equipment as an additional level of protection.
In many installations, different SPD types can work together to create a coordinated protection strategy.
Frequently Asked Questions
What does SPD stand for?
SPD stands for Surge Protection Device.
It is designed to limit transient overvoltages and divert surge currents to help protect an electrical installation and connected equipment.
What is the difference between Type 1 and Type 2 SPD?
A Type 1 SPD is generally associated with the incoming side of an installation and higher-energy surge protection.
A Type 2 SPD is commonly installed at distribution boards and provides another level of protection within the installation.
What is the difference between Type 2 and Type 3 SPD?
Type 2 SPDs are generally used at distribution level.
Type 3 SPDs are used closer to sensitive equipment and provide additional local protection.
Can I install an SPD myself?
SPD installation involves electrical connections and protection coordination.
For safety, selection and installation should be handled by a qualified electrical professional who can assess the electrical system and applicable requirements.
Does an SPD protect against every electrical problem?
No.
An SPD is designed for transient overvoltage protection. It does not replace other protective devices such as MCBs, RCCBs or RCBOs.
Each protection device has a specific role in an electrical installation.
Final Thoughts
Understanding the difference between Type 1 vs Type 2 vs Type 3 SPD makes it easier to understand how surge protection works in an electrical installation.
Type 1, Type 2 and Type 3 devices serve different roles. In some installations, they can be used together as part of a coordinated protection strategy.
However, the right SPD depends on the electrical system, building characteristics, connected equipment and applicable requirements.
Before purchasing or installing an SPD, check the manufacturer’s technical specifications and consult a qualified electrical professional.
Looking for electrical protection products?
Spade Supplies can help you find suitable electrical products for residential, commercial and industrial requirements. Speak with the team about your project and product requirements.
