Selecting the wrong surge protective device can leave your solar system vulnerable to costly damage. Many installers make critical SPD selection errors that compromise protection and waste money on inappropriate equipment.

The 10 most common SPD selection mistakes include: 1) installing incorrect types for specific locations, 2) misunderstanding kA ratings¹ between different waveforms, 3) improper voltage coordination with equipment, 4) overlooking regional installation standards, 5) neglecting temperature derating factors, 6) ignoring protection coordination between cascaded devices, 7) selecting based on price alone, 8) missing required disconnection features, 9) improper grounding integration, and 10) failing to account for system-specific requirements like PV voltage fluctuations. Type 1 SPDs² handle direct lightning at service entrances, Type 2 manage induced surges at distribution panels, and Type 3 protect sensitive equipment near point-of-use, with proper kA ratings calculated based on location-specific risk assessment.

These mistakes aren’t just technical oversight—they’re costly errors that can lead to premature equipment failure and system downtime. With over 12 years in electrical manufacturing, I’ve seen how proper SPD selection is crucial for long-term system reliability. Let me help you avoid these common pitfalls.

Which type of SPD is best located at the origin of an installation when considering SPD type and location?

Many installers place Type 2 SPDs at service entrances, leaving systems vulnerable to direct lightning strikes. This mistake can result in catastrophic damage to your entire electrical infrastructure.

Type 1 SPDs are specifically designed for installation at the origin (service entrance) of electrical systems where direct lightning strikes are possible. These devices can discharge high-energy lightning currents (10/350μs waveform) and provide the first line of defense against external surges entering your installation.

When planning your surge protection strategy, location matters tremendously. The SPD classification system (Types 1-3) exists specifically to guide proper placement throughout your electrical system. Type 1 devices belong at the origin because they’re tested with the 10/350μs impulse current waveform that simulates direct lightning strikes. These robust devices can handle the highest surge energies.

Type 2 SPDs, while excellent for distribution panels, lack the robust design needed to handle direct lightning energy. They’re tested with the 8/20μs waveform, which represents induced surges, not direct strikes. Installing a Type 1 device at your service entrance provides comprehensive upstream protection that reduces the burden on downstream protection devices.

For critical solar installations, especially in high lightning-risk zones, I recommend our SOWER DC-SPD-T1 series with high discharge capacity. We’ve seen clients in lightning-prone regions of Southeast Asia significantly reduce lightning-related failures after upgrading to proper Type 1 protection at their service entrances.

What type of SPD do I need?

Installers often choose a one-size-fits-all approach to surge protection, installing identical SPDs throughout the system. This not only wastes money but leaves critical vulnerabilities in your protection scheme.

You need a coordinated approach using different SPD types based on location: Type 1 for service entrances with lightning risk, Type 2 for distribution panels, and Type 3 for protecting sensitive equipment. For solar systems, DC-specific SPDs are essential for the DC side, while AC SPDs protect the inverter output and grid connection.

Choosing the right SPD involves understanding your specific system needs and environmental factors. Solar installations face unique challenges because they need protection on both DC and AC sides. On the DC side, string combiner boxes need robust SPDs because they’re often mounted outside where lightning strikes are possible.

For comprehensive protection, follow these selection guidelines:

I recently consulted on a large installation in North America where the client had initially planned to use only Type 2 devices throughout. After reviewing their lightning exposure and system layout, we implemented a coordinated protection scheme that included Type 1 devices at exposed DC combiner boxes. During a severe thunderstorm six months later, the system remained fully operational while a neighboring installation suffered significant inverter damage.

How to calculate SPD rating?

Many installers simply choose SPDs with the highest kA rating they can afford, not understanding that proper calculation involves multiple factors. This approach wastes money without providing optimal protection.

Calculate SPD ratings by first determining the system’s maximum continuous operating voltage³ (MCOV), then assess your lightning risk exposure⁴ to determine required discharge capacity. For solar DC systems, ensure the SPD voltage rating exceeds the maximum open circuit voltage (Voc) accounting for temperature factors, typically 1.2× Voc.

Properly calculating SPD ratings requires careful consideration of both voltage coordination and surge current capacity. For voltage coordination, your SPD must have a voltage protection level (Up) lower than the equipment’s impulse withstand voltage (Uw). This creates a safety margin ensuring surges don’t exceed what your equipment can handle.

For solar DC applications, voltage calculations must account for environmental factors. Solar panels can produce higher voltages in cold temperatures, so your SPD must handle these peaks. I use this formula for DC solar applications:

MCOV rating = Voc × 1.2 × Number of panels in series

The surge current capacity needs careful assessment based on:

I’ve seen installations where installers selected 40kA Type 2 SPDs for every location, regardless of actual need. This increased their costs significantly without providing additional protection benefits. For a recent project in South America, we conducted a thorough risk assessment and were able to recommend a combination of 12.5kA and 20kA devices that provided appropriate protection while reducing the client’s costs by nearly 20%.

What does kA mean on a surge protector?

Many buyers focus solely on the kA number, believing higher is always better, without understanding what this specification actually measures. This misconception leads to overpriced purchases that don’t necessarily improve protection.

kA (kiloamperes)⁵ on a surge protector indicates its maximum surge current capacity—how much electrical current it can safely divert during a surge event. For Type 1 SPDs, this is measured with a 10/350μs impulse, while Type 2 uses an 8/20μs waveform, making direct comparisons misleading.

The kA rating represents the device’s ability to handle surge current without failing, but there’s significant confusion about how to interpret these numbers. For Type 1 SPDs, the important parameter is Iimp (impulse current), measured with the 10/350μs waveform that represents direct lightning. For Type 2 devices, we look at Imax (maximum discharge current) using the 8/20μs waveform for induced surges.

These waveforms differ dramatically in energy content:

I often see confusion when clients try to compare a 20kA Type 1 device with a 40kA Type 2 device. Despite the higher number, the Type 2 device handles less total energy. This misconception can be costly—a client in Africa recently installed high-kA Type 2 devices at their service entrance, believing the higher number offered better protection. Unfortunately, during a direct lightning strike, these devices failed because they weren’t designed for the lightning impulse waveform, resulting in expensive equipment damage.

How to choose a good surge protector?

Installers often select surge protectors based solely on price or brand recognition, neglecting critical performance parameters. This approach frequently results in inadequate protection and wasted investment.

Choose a good surge protector by verifying it has proper safety certifications (UL1449, IEC 61643)⁶, voltage ratings matching your system, appropriate surge capacity⁷ for your risk level, and low voltage protection level (Up). Ensure it includes thermal disconnection, status indicators, and is from a reputable manufacturer offering warranty support.

Selecting quality surge protection involves evaluating several critical factors beyond just price. First, ensure the device meets relevant standards for your region—UL1449 in North America and IEC 61643 internationally. These certifications verify the device has undergone rigorous safety testing.

Beyond certification, examine these critical specifications:

Manufacturing quality is equally important. At SOWER, our production includes 100% testing of each SPD unit before shipping. This attention to quality control has resulted in a remarkably low field failure rate compared to industry averages.

I recently visited an installation where the client had chosen the cheapest available SPDs without checking specifications. These devices lacked proper disconnection mechanisms and status indicators. During a routine inspection, we discovered several had failed silently, leaving the system unprotected for an unknown period. Replacing these with properly specified devices actually saved money in the long run by preventing potential equipment damage.

Conclusion

Selecting the right SPD requires understanding system needs, proper placement of Types 1-3 devices, accurate voltage and kA calculations, and quality assessment. Avoid these common mistakes to ensure reliable, cost-effective surge protection for your solar installation.