The Schneider Electric A9L40172 is a Type 2 surge protective device cartridge from the Acti9 range, designated C40-800 PV. It's the replaceable MOV element for the iPRD PV-DC 2P base unit — a modular, plug-in cartridge rated for photovoltaic DC applications. The 800 V DC maximum continuous operating voltage (Uc) and 40 kA maximum discharge current (Imax) position it for combiner boxes and inverter DC sides on commercial PV arrays, where the string voltage pushes past the 600 V DC common on residential gear.
800 V DC Uc means this cartridge can sit on a 600 V nominal PV string and still have headroom for the 1.25× voltage rise code requires (NEC 690.7). The 40 kA Imax is the single-shot survival rating — it can absorb one 40 kA 8/20 µs surge without failing short. The nominal discharge current (In) of 15 kA is the rating that governs its endurance through repeated strikes; that's the number to use for coordination studies. Protection level Up is clamped under 1.4 kV, which keeps the DC bus voltage within the typical 1.5 kV insulation withstand of most PV inverters. Response time under 25 ns means it catches the leading edge of a lightning-induced transient before the inverter's internal DC-link capacitors see the full voltage rise.
This is a plug-in cartridge — it snaps into the iPRD PV-DC 2P base module, not directly onto a DIN rail. The base module carries the rail clips and the wiring terminals; the cartridge is the serviceable element. The white (RAL 9003) housing has a local flag indicator that flips from white to red when the MOV has degraded beyond its safe operating window. Two 9 mm pitch positions on the base. IP20 on the front face — panel-mount only, not for outdoor exposure without an enclosure.