What this MCCB is and what it does
The Siemens 3VA1120-3EF36-0JA0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection — the primary overcurrent and short-circuit safeguard in a distribution panel or motor control center. It carries a continuous 20 A rating that holds flat from 40 °C through 55 °C, then derates to 19 A at 60 °C and 65 °C, and stays at 19 A up to 70 °C. That means in a warm cabinet — say, a non-ventilated enclosure near a line reactor — you still get the full 20 A up to 55 °C before any reduction kicks in. Breaking capacity is the number that decides whether this breaker clears a fault or welds shut. At 240 V it interrupts 75.6 kA; at 415 V it handles 52.5 kA; at 440 V it drops to 32 kA; at 500 V and 690 V it holds at 11.9 kA. For a 20 A frame, those are high-interrupt ratings — this breaker is sized for a strong fault-current bus, not a light residential panel. The overcurrent release is a TM240 — a thermal-magnetic unit with a fixed thermal pickup at 20 A and a magnetic trip that responds to short-circuit currents. There is no undervoltage release, no shunt trip beyond the listed auxiliary release, no ground-fault monitoring module, and no communication function built in. It is a straight line-protection breaker: install it, feed it, and it trips on overcurrent or short.
Panel fit and integration
Dimensions are 130 mm tall, 76.2 mm wide, and 70 mm deep — a standard 3-pole MCCB footprint that drops into a SENTRON panelboard or onto a DIN-rail adapter without reworking the gland plate. The 800 V rated insulation voltage gives headroom for 480 V and 600 V class systems. Operating temperature range is -25 °C to 70 °C, storage from -40 °C to 80 °C. Maximum power loss is 12 W at rated load — negligible for thermal budgeting in a ventilated enclosure, but worth noting if you are packing multiple breakers into a sealed box.