What this trip unit does
The C104TM040 is a TM-D thermal-magnetic trip unit for Schneider Electric ComPacT NSX100…250 circuit breakers. It provides LI protection — thermal overload (L) and magnetic short-circuit (I) — for a 40 A circuit at 40 °C ambient. The 4-pole 4D configuration protects all four poles, with the neutral on the left and neutral protection set at 1 x Ir.
The instantaneous magnetic trip is fixed at 500 A (Ii), so on a 40 A circuit it clears a short-circuit fault at roughly 12.5 x In. That's a steep magnetic pickup; expect good selectivity with downstream MCBs or fuses rated below 40 A. Long-time pickup (Ir) is adjustable from 0.7 to 1 x In, giving you a 28–40 A thermal range to match cable ampacity or derating needs. The fixed long-time delay (tr) is 120–400 s at 1.5 x In, with a fast 15 s at 6 x Ir for high overloads — typical for distribution feeder protection.
This is a trip unit, not a standalone breaker — it snaps into a ComPacT NSX100, NSX160, or NSX250 frame. The fixed mounting mode means it's intended for panelboard or enclosure installation, not plug-in.