What it is and what the ratings mean
The Siemens 3VA1120-4GD42-0AA0 is a SENTRON 4-pole molded case circuit breaker (MCCB) rated 20 A continuous at 40 °C, with a TM210 thermal-magnetic trip unit — a fixed thermal and fixed magnetic release designed for line protection in distribution panels and motor branch circuits. The interrupting ratings tell you where this breaker can safely clear a fault: 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at 500 V and 690 V. That 121 kA figure at 240 V means it handles high-fault-capacity service-entrance or sub-distribution boards without needing a current-limiting fuse upstream — a real spec for high-available-fault installations. Thermal derating is flat from 40 °C through 55 °C at 20 A, then drops to 19 A at 60 °C through 70 °C. If the panel ambient runs hot, you can still load it at 19 A without tripping — no need to oversize the frame. Rated insulation voltage Ui is 800 V, and the maximum DC operational voltage is 600 V — relevant if this breaker lands in a DC-coupled PV combiner or battery rack application.
Sourcing and lifecycle
The 4-pole construction with 100 % N-conductor protection means the neutral pole opens and closes with the phases — required for TN-S or TT systems where the neutral must be switched.
Integration and compliance
Mounts on a DIN rail or panel-mount base; the 70 mm depth and 101.6 mm width fit standard SENTRON 3VA panel cutouts. IP40 on the front face suits enclosed distribution boards — no washdown rating, so keep it behind a panel door in wet environments. Power loss is 12 W maximum at rated current — negligible for thermal budgeting in a populated panel, but worth noting if the enclosure is tightly sealed. The TM210 release is a fixed thermal-magnetic design — no interchangeable trip units, no communication module, no ground-fault monitoring. It is a straight line-protection breaker for simple overcurrent and short-circuit duty.