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

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.

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.

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.

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).

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.

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.

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.

It is available through Shansen Enterprises, an authorized channel partner for Mersen products. Shansen offers pan-India delivery and quick WhatsApp-based quotations.