What it is and what it does
The Siemens 3VA1020-4ED36-0BA0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection — the primary overcurrent guard on a feeder or distribution branch. It carries a 20 A rating at 40 °C (flat to 55 °C, then derating to 19 A at 70 °C) across three poles, with a TM210 thermal-magnetic overcurrent release that handles both overload and short-circuit trip curves. The 121 kA breaking capacity at 240 V tells you this breaker can interrupt a fault up to that level without welding contacts or cascading upstream — critical for high-fault panels near transformers or large drives. An undervoltage release (UVR) is built in, so the breaker drops out when control voltage falls below the dropout threshold, a common requirement for emergency-stop chains or undervoltage protection schemes.
Breaking capacity across voltages
The interrupting rating varies with system voltage: 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at both 500 V and 690 V. That drop at higher voltages is typical for a thermal-magnetic MCCB — the arc extinction gets harder as voltage rises. For a 400 V distribution panel, the 75.6 kA figure gives substantial SCCR headroom against most transformer-fed faults. The 800 V rated insulation voltage (Ui) confirms the breaker's internal clearance and creepage are designed for 690 V line-to-line systems.
Panel fit and integration
The breaker measures 76.2 mm wide, 130 mm tall, and 70 mm deep — a standard 3-pole MCCB footprint that fits Siemens' own SENTRON mounting plates and most DIN-rail adapters. The 14.5 W maximum power loss at rated current matters for enclosure thermal calculations: in a sealed panel with multiple breakers side by side, that heat adds up. Operating range spans -25 °C to 70 °C ambient, storage from -40 °C to 80 °C. The supplied basic switch (3VA10204ED360AA0) is the core switching mechanism; the order code adds the UVR and TM210 release as factory-installed options.