What this MCCB is and what it does
The Siemens 3VA1020-4ED36-0KA0 is a SENTRON molded case circuit breaker (MCCB) rated for 20 A continuous current, with a TM210 thermal-magnetic overcurrent release. It is a 3-pole unit designed for line protection — meaning it sits at the feeder or branch circuit, not on a specific motor or load. The 121 kA breaking capacity at 240 V tells you it can safely interrupt a massive fault without welding contacts or cascading upstream; at 415 V it still handles 75.6 kA, and at 690 V it holds 11.9 kA. That spread makes it suitable for high-fault panels where the available short-circuit current is high — think industrial switchboards or transformer secondaries.
Fit and mounting
The 3VA1020-4ED36-0KA0 measures 130 mm high, 76.2 mm wide, and 70 mm deep. It mounts on a DIN rail or directly to a backplate via the MCCB's integral mounting feet. The front face carries an IP40 protection class — fine for a clean indoor panel, but not for washdown environments. Three-pole means it breaks all phases simultaneously; there's no undervoltage release or ground-fault monitoring on this variant, so those functions would need an external relay or shunt trip if your circuit requires them.
Thermal derating and power loss
This MCCB carries its full 20 A rating from 40 °C up to 55 °C. At 60 °C it derates to 19 A, and holds that through 70 °C. That's a clean thermal curve — no surprise drop at moderate cabinet temperatures. Maximum power loss is 12 W, which is modest for a 20 A MCCB; it won't drive a lot of heat into a densely packed panel.