What it is and what it does
The Merlin Gerin NG125NC16A is a 2-pole miniature circuit breaker from the Multi9 NG125N series, rated at 16 A with a C-trip curve. It protects branch circuits against overloads and short circuits in commercial and light industrial panels. The C curve means the magnetic trip operates at 5 to 10 times the rated current (80 to 160 A), which suits it for resistive and moderate inductive loads like lighting banks, small transformers, and general-purpose outlets. For motor circuits with higher inrush, a D-curve breaker would be the better pick. Breaking capacity is 50 kA at 220/240 V AC — that's the maximum fault current it can safely interrupt without welding or rupturing. At the rated operational voltage of 380/415 V AC, the breaking capacity will be lower per the manufacturer's derating curve; check the coordination tables if you're feeding a high-fault panel.
Panel fit and environment
Snaps onto DIN rail; dimensions are 81 x 103 x 54 mm, so it takes up a standard 2-module width. Torque the terminals to 3.5 Nm — that's the spec for the screw clamps, and under-torquing is the most common cause of thermal trip nuisance in the field. Rated for ambient temperatures from -30 to 70 °C, which covers most indoor panel environments and unheated enclosures. No IP rating is listed on this entry, so it's a standard open-panel breaker — not for washdown or outdoor exposure without an enclosure.
Standards and compliance
Designed to IEC 60947-2, the standard for low-voltage switchgear and controlgear circuit breakers. The rated insulation voltage is 690 V, and impulse withstand is 8 kV — figures that matter for coordination with upstream surge protection.