What the ratings mean for fit
The 3VA1120-4EF32-0BC0 from the Siemens SENTRON family is a 3-pole molded case circuit breaker (MCCB) rated 20 A continuous at 40 °C ambient, with a thermal derating curve that holds 20 A up to 55 °C and drops to 19 A at 70 °C. That 20 A rating at elevated panel temperatures is the figure that governs real-world loading — the breaker carries its full nameplate current inside a warm enclosure, not just at a lab 40 °C. Breaking capacity is the headline number for fault clearance: 121 kA at 240 VAC, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at both 500 V and 690 V. At 240 V this breaker safely interrupts faults up to 121 kA without cascading upstream — it is sized for high-fault panels where a standard 25 kA or 65 kA MCCB would weld its contacts on a bolted fault. The design is line protection (not motor or generator protection), with an undervoltage release (UVR) built in. The UVR trips the breaker when supply voltage drops below a set threshold — a common requirement for emergency-stop circuits or undervoltage ride-through schemes in safety-critical panels. No communication function, no ground-fault monitoring, no trip indicator.
Panel integration and footprint
70 mm depth (2.76 in), 76.2 mm width (3 in) per pole, 130 mm height (5.12 in). Rated insulation voltage 800 V. Operating temperature -25 °C to +70 °C; storage -40 °C to +80 °C. Maximum power loss 14.5 W.