What this MCCB is and what it does
The Siemens 3VA1120-5GD42-0AA0 is a SENTRON 4-pole molded case circuit breaker (MCCB) rated for line protection in distribution panels. The TM210 thermal-magnetic release gives it a continuous current rating of 20 A that holds flat from 40 °C through 55 °C, then derates to 19 A at 60–70 °C — useful to know if the breaker sits in a warm enclosure or next to other heat sources. Interrupting capacity is the headline here: 187 kA at 240 V AC, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at 500 V and 690 V. That 187 kA figure at 240 V means it can clear a massive fault without venting or cascading upstream — relevant for high-fault panels near large transformers or in industrial mains positions. Rated insulation voltage Ui is 800 V, and max DC operational voltage is 600 V, so it handles mixed AC/DC bus applications within those limits. The front face carries IP40 protection — fine for a closed panel, but not for washdown or outdoor exposure without an additional enclosure.
Panel fit and integration notes
Physical footprint: 130 mm height, 101.6 mm width (4 inches), 70 mm depth. The 4-inch width is standard for a 4-pole MCCB in this class — it occupies the same DIN-rail or mounting-plate slot as other SENTRON 3VA four-pole units. The optional motor drive (listed as available) allows remote tripping or reclose in automated panels. Power loss is 12 W maximum at rated load. In a densely packed panel, that's modest but not trivial — factor it into your thermal budget if the enclosure is sealed or tightly louvered.