What this MCCB carries — and where it fits
The Siemens 3VA1120-6EF36-0JC0 is a 3-pole SENTRON molded case circuit breaker rated for 20 A continuous at 40 °C, with a TM240 thermal-magnetic overcurrent release and a shunt trip (STL) auxiliary release that triggers on voltage. Its interrupting capacity hits 220 kA at 240 V, 154 kA at 415 V, and 121 kA at 440 V — numbers that tell you it's built for high-fault panels where downstream coordination matters. The 800 V rated insulation voltage (Ui) gives headroom on 480 V or 600 V class systems without derating the dielectric. It ships with two HQ auxiliary switches, no undervoltage release, and no phase-failure detection; the front carries IP40 protection, so it's fine inside a clean enclosure but not washdown.
What the ratings mean for fit
The 220 kA at 240 V is the headline SCCR — it safely interrupts faults up to that level without cascading upstream, which is what you need for a main breaker in a high-fault panel. The 20 A continuous rating holds flat from 40 °C to 50 °C, then derates to 18 A at 70 °C; if your enclosure runs hot, that derating curve (–) decides the actual ampacity. The TM240 release is a fixed thermal-magnetic unit — no electronic adjustment, no communication. The shunt trip (STL) means a remote voltage signal can trip the breaker, handy for emergency-stop or fire-alarm integration. The 2 HQ auxiliary switches give status feedback; no undervoltage release is fitted, so a voltage dip won't drop the load automatically.