The 40 A rating holds flat from 40 °C up to 50 °C, then derates to 39 A at 55–60 °C, 38 A at 65 °C, and 37 A at 70 °C — so in a warm panel or enclosure you lose 3 A at the top end. The breaking capacity tells you where it can safely interrupt a fault: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at both 500 V and 690 V.
Dimensions are 130 mm height, 101.6 mm width, 70 mm depth — a 4-pole footprint that fits standard Siemens SENTRON panel cutouts. The TM220 trip unit is non-interchangeable, so the protection curve is fixed at the factory; no field-swap of trip modules.
What the TM220 trip unit means for protection
The TM220 designation indicates a thermal-magnetic trip with fixed settings: the thermal element (for overload protection) is calibrated to the 40 A rating, and the magnetic element (for short-circuit protection) has a fixed pickup. There is no ground-fault monitoring version, no undervoltage release, and no communication function — this is a basic, no-frills line-protection breaker. The maximum power loss is 10.8 W, which matters for heat buildup in a sealed enclosure.