MCCB for line protection — 20 A, 3-pole, TM240 release
The Siemens SENTRON 3VA1120-4EF36-0DC0 is a 3-pole molded case circuit breaker rated for 20 A continuous current (Iu) with a TM240 thermal-magnetic overcurrent release. It is designed for line protection in distribution panels, not motor or feeder protection — the TM240 release curve is fixed for cable and busbar protection, not adjustable for inrush. Interrupting capacity is 121 kA at 240 V AC, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at 690 V — these figures cover most low-voltage distribution scenarios up to the 690 V tier. The 121 kA at 240 V is the headline number for high-fault panels; the 75.6 kA at 415 V is the one that matters for 400 V-class European distribution. Rated insulation voltage is 800 V, giving headroom for 690 V systems. The breaker carries an undervoltage release (UVR) as standard — if control voltage drops, the breaker trips, which is useful for emergency-stop circuits or undervoltage protection schemes. Thermal derating is flat from 40 °C to 50 °C at 20 A, then drops to 19.2 A at 55 °C, 18.8 A at 60 °C, 18.4 A at 65 °C, and 18 A at 70 °C. In a sealed panel running at 55 °C ambient, you lose 0.8 A — plan your load margin accordingly.
Integration and mounting
Dimensions are 76.2 mm wide, 130 mm high, 70 mm deep. The 76.2 mm width is a standard 3-pole MCCB footprint — fits most DIN-rail or panel-mount enclosures without adapter plates. IP40 on the front means it's protected against tools and small wires entering the front face; not rated for washdown or outdoor exposure. Auxiliary contact version is 2 auxiliary switches HQ (high-qualified), providing two changeover contacts for status feedback to a PLC or indication lamp. The integrated auxiliary trip is order code 3VA9608-0BB25 — if you need a shunt trip or additional aux contact, that's the companion module. Latching endurance is rated at 15,000 operations.
Lifecycle and sourcing
Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The storage minimum matters for unheated warehouses in cold climates — the breaker can sit at -40 °C without damage, but must be warmed above -25 °C before energizing.