What this MCCB is and what it does
The Siemens SENTRON 3VA1120-5EF36-0DC0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection, carrying a continuous current of 20 A across the 40 °C to 55 °C band and derating to 19 A at 60 °C and above. Its interrupting capacity at 240 V is 187 kA, dropping to 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at 500 V and 690 V — figures that tell you it handles high-fault scenarios on the secondary side of a distribution transformer or in a main feeder position. The part includes an undervoltage release (UVR) and two HQ auxiliary switches, so it can signal its state back to a PLC or safety circuit without an add-on module.
Panel fit and integration
The 3VA1120-5EF36-0DC0 measures 130 mm high, 76.2 mm wide, and 70 mm deep — a standard 3-pole MCCB footprint that mounts on a DIN rail or bolted directly to a backplate. At 14.5 W maximum power loss, it needs no forced cooling in a ventilated enclosure, but keep the derating curve in mind if the ambient inside the panel pushes past 55 °C. The UVR coil draws its signal from the line side; verify the control voltage matches your system before wiring.