What this breaker is and what it does
The Siemens 3VA1120-4EF32-0KA0 is a 3-pole SENTRON molded case circuit breaker (MCCB) for line protection, carrying a rated continuous current Iu of 20 A and a TM240 thermal-magnetic overcurrent release. The breaking capacity at 240 V hits 121 kA, at 415 V it's 75.6 kA, at 440 V it's 52.5 kA, and at 690 V it drops to 11.9 kA — that's the sort of short-circuit headroom you need for high-fault panels where the upstream transformer can dump serious energy into a bolted fault. The breaker is fitted with a shunt trip (STL) auxiliary release (design of the auxiliary release: shunt trip), so it can be tripped remotely by a voltage signal — useful for emergency-stop circuits or supervisory shutdown sequences. No undervoltage release, no auxiliary contacts, no communication module, and no ground-fault monitoring on this variant; it's a straightforward thermal-magnetic MCCB with a remote-trip option.
Thermal derating and operating envelope
The 20 A rating holds flat from 40 °C up to 50 °C — no derating needed in a warm panel. At 55 °C it drops to 19.2 A, at 60 °C to 18.8 A, at 65 °C to 18.4 A, and at 70 °C to 18 A. If your enclosure sits near a drive or transformer and ambient regularly hits 55 °C, plan for that 0.8 A reduction. Operating ambient range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The front face carries IP40 protection — fine for a clean panel interior, but not for washdown or outdoor exposure without a secondary enclosure.
Physical fit in the panel
The breaker measures 130 mm high, 76.2 mm wide, and 70 mm deep. That 76.2 mm width is three 25.4 mm pole modules — standard for a 3-pole MCCB on a DIN rail or bolted to a backplate. The 70 mm depth is shallow enough to clear most 200 mm deep enclosures with room for wiring behind. No trip indicator on the front, so you'll need to verify status via the handle position or a remote auxiliary contact (not included on this variant).