Type 1+2 vs. Separate SPDs: Which Surge Protection Strategy Is Best?

Electrical surges threaten your expensive equipment and critical systems daily. Without proper protection, you’re gambling with thousands of dollars in potential damage and dangerous electrical failures.

The best surge protection strategy depends on your specific needs. Type 1+2 combination SPDs¹ offer space-saving convenience and comprehensive protection in one unit, while separate Type 1 and Type 2 SPDs provide targeted protection with potentially better performance in specialized applications.

I’ve been in the electrical protection industry for years, and the question about combined versus separate surge protection devices (SPDs) comes up constantly. Let me walk you through everything you need to know to make the right decision for your system.

Which SPD Class Is Used for Surge Arresters?

Lightning strikes and power surges can destroy equipment in milliseconds. Without the right protection class, your entire electrical system remains vulnerable to catastrophic damage.

For surge arresters, Type 1 (Class I) SPDs are used at service entrances to protect against direct lightning strikes. Type 2 (Class II) SPDs protect branch circuits from switching surges and residual lightning energy. Type 3 SPDs provide fine protection for sensitive equipment.

Choosing the right SPD class is crucial for effective protection. Type 1 SPDs are tested with a 10/350μs impulse waveform, simulating direct lightning strikes. These heavy-duty protectors are installed at the main distribution board where the power enters the building. They can discharge the enormous energy from a direct lightning strike.

Type 2 SPDs, tested with an 8/20μs impulse, handle lower energy surges from indirect lightning effects and switching operations. They’re typically installed in sub-distribution boards to provide secondary protection. Type 3 SPDs offer the finest protection level but have the lowest energy handling capability. They’re installed near sensitive equipment as a final defense.

In many photovoltaic applications, I recommend Type 1+2 combination devices which merge the capabilities of both classes. This approach offers comprehensive protection while reducing installation space and complexity, particularly valuable in constrained electrical cabinets.

What Is the Difference Between Class 1 and Class 2 Lightning Protection?

Your expensive equipment faces different types of surges. Using the wrong protection class could leave critical vulnerabilities in your system.

Class 1 (Type 1) lightning protection² handles direct lightning strikes with high impulse currents (10/350μs waveform) up to 25kA or more per pole. Class 2 (Type 2) protection manages indirect strikes and switching surges with lower energy (8/20μs waveform) up to 40kA per pole.

The fundamental difference lies in their energy handling capabilities and intended installation points. Class 1 SPDs use robust spark gap technology to divert massive lightning energies safely to ground. Their ability to handle high-energy 10/350μs impulses makes them essential at service entrances, particularly in structures with external lightning protection systems.

Class 2 protectors typically utilize Metal Oxide Varistors (MOVs) for surge suppression. While they can’t handle direct lightning strikes, they’re excellent at managing the residual energy that passes through Class 1 devices and surges from switching operations within the power system.

For context, a typical lightning strike can produce currents exceeding 30,000 amperes, with some reaching 200,000 amperes. Class 1 protectors are designed to handle this massive energy, while Class 2 devices manage the reduced surge energy further downstream.

In our SOWER manufacturing facilities, we’ve developed specialized DC surge protectors for both classes to meet the unique demands of solar photovoltaic systems where DC surges pose significant threats to inverters and other components.

How Do I Choose My Lightning Protection Level?

Selecting inadequate protection levels puts your electrical systems at unnecessary risk. Without understanding protection level calculations, you might waste money on excessive protection or leave dangerous gaps.

Choose your lightning protection level based on your equipment’s impulse withstand voltage and risk assessment. For sensitive electronics (Category I), select SPDs with a voltage protection level (Up) below 1.5kV. For robust industrial equipment (Category IV), Up values up to 6kV may be acceptable.

Your lightning protection level selection should be based on a systematic risk assessment following standards like IEC 62305. Start by categorizing your equipment according to its overvoltage category:

Next, assess your building’s exposure risk. Consider factors like:

• Geographic location and lightning frequency
• Building height and isolation
• Value and criticality of protected equipment
• Consequences of failure (safety, financial, operational)

Protection levels range from I (highest protection) to IV (basic protection). For critical facilities like hospitals or data centers, I typically recommend protection level I or II. For standard commercial buildings, level III often provides adequate protection.

Remember that the SPD’s voltage protection level (Up) must be lower than your equipment’s impulse withstand voltage with a proper safety margin. This coordination ensures surges are diverted before they can damage your equipment.

What Is the Best Number of Joules For a Surge Protector?

Buying surge protectors without understanding joule ratings could leave your valuable equipment vulnerable. Many people waste money on inadequate protection because they don’t know what the numbers really mean.

For whole-house or industrial surge protection, look for Type 1 SPDs with energy handling capacity of 10,000+ joules. For branch circuit protection, Type 2 SPDs with 1,000-5,000 joules are appropriate. For sensitive electronics, add Type 3 protectors with 600-1,000 joules.

The joule rating indicates how much energy a surge protector can absorb before failing. However, this specification doesn’t tell the complete story. While consumer-grade power strips might advertise high joule ratings (1,000-2,000), their clamping voltage and response time are equally important factors.

For industrial and commercial applications, I focus less on joule ratings and more on surge current capacity³ (kA) and voltage protection level (Up). These metrics more accurately reflect performance in professional settings. A properly designed protection scheme includes multiple layers:

For photovoltaic systems, I’ve found that DC surge protectors need special consideration due to the unique characteristics of DC arcs. Our SOWER DC SPDs are specifically engineered with higher surge current capacities (up to 40kA) to ensure reliable protection of solar inverters and maximize system uptime.

Remember that higher joule ratings generally indicate longer service life, as the SPD can absorb more surges before requiring replacement. However, extremely high-energy surges may still overwhelm even high-joule devices, which is why a layered protection approach is always best.

Conclusion

For optimal surge protection, assess whether Type 1+2 combination devices suit your space and budget constraints, or if separate SPDs would provide better specialized protection for your specific application. Regular inspection of your surge protection devices ensures continued equipment safety.