What this 3VA1120-3EF36-0BC0 is and what it does
The Siemens 3VA1120-3EF36-0BC0 is a SENTRON molded case circuit breaker (MCCB) rated for line protection in three-phase distribution. It carries a continuous current of 20 A at 40 °C and holds that rating up to 50 °C; above that it derates to 19.2 A at 55 °C and 18 A at 70 °C. The interrupting capacity scales with system voltage — 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 10.5 kA at 690 V — so it handles high-fault scenarios on 400 V class panels without cascading upstream. The TM240 thermal-magnetic release provides fixed time-current characteristics for overload and short-circuit protection. An integrated undervoltage release (UVR) is fitted as standard, and two HQ auxiliary switches are built in for status feedback to a PLC or annunciator.
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 drops into most SENTRON panelboards and distribution blocks without re-drilling. The front face carries an IP40 protection class, adequate for enclosed switchgear but not for washdown environments. The undervoltage release and auxiliary switches are factory-installed; no field-assembly of those accessories is needed.
What the key ratings mean for the buyer
The 75.6 kA interrupting rating at 240 V means this breaker can safely clear a fault current up to that level without rupturing — critical for high-capacity transformer secondaries or industrial feeders. The 20 A continuous rating is the maximum load it can carry indefinitely at 40 °C ambient; if your panel runs hotter than 50 °C, you must derate to 19.2 A or lower. The 800 V rated insulation voltage (Ui) tells you the breaker is suitable for 690 V line-to-line systems, which is common in European industrial networks. The TM240 release is a fixed thermal-magnetic type — no interchangeable trip units, so the 20 A rating is locked in at the factory.