Mersen STPT2-40K320V-4P Surge Protection Device FAQ

Why this FAQ?

This FAQ helps electrical engineers, panel builders, and maintenance teams quickly understand the specifications, installation, and sourcing details of the Mersen STPT2-40K320V-4P SPD for safe and reliable surge protection.

[faq question=”What is the Mersen STPT2-40K320V-4P Surge Protection Device used for?”]
The Mersen STPT2-40K320V-4P is a Type 2 (Class II) SPD designed to discharge transient overvoltages (surge currents) in low-voltage power networks. It provides secondary surge protection in main or sub-distribution panels, typically installed downstream of a Type 1 SPD or as primary protection in systems without external lightning exposure.
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[faq question=”What are the electrical ratings of the Mersen STPT2-40K320V-4P?”]
It is rated for 277/480 V AC (3Ph+N, 4+0 TNS) systems, with a nominal discharge current (In) of 20 kA and a maximum discharge current (Imax) of 40 kA (8/20 µs waveform). The short-circuit withstand capacity (ISCCCR) is 25 kA.
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[faq question=”Which standards does the Mersen STPT2-40K320V-4P comply with?”]
This SPD complies with EN/IEC 61643-11 for surge protective devices and meets RoHS environmental compliance. It is classified as Type 2 (IEC) and UL Type 2 component assembly.
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[faq question=”How is the Mersen STPT2-40K320V-4P installed and maintained?”]
The device mounts on a DIN rail and uses pluggable protection modules for easy replacement. Tighten terminals to 3 N·m torque. The built-in visual indicator shows green (OK) or not green (replace) status. Replacement plug part number: 77707671 (for both L-N and N-PE).
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[faq question=”What are the voltage protection ratings (VPR) for this SPD?”]
The voltage protection ratings are: L-G 1000 V, L-L 2000 V, N-G 1000 V, and L-N 2000 V. These indicate the maximum let-through voltages during surge events.
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[faq question=”What backup protection and fuse rating are required?”]
A maximum 125 A gG type backup fuse is recommended for each protected phase to ensure coordination and safety in the event of overcurrent conditions.
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[faq question=”What is the physical construction and material of the device?”]
The housing is made of PA66 (CTI 1) thermoplastic, ensuring electrical insulation and flame resistance. Dimensions are approximately 72 × 70 × 90 mm, with a weight of about 0.4 kg.
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[faq question=”Where can I buy the Mersen STPT2-40K320V-4P in India?”]
It is available through Shansen Enterprises, an authorized channel partner for Mersen products. Shansen offers pan-India delivery and quick WhatsApp-based quotations.
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