What it is and what it does
The Siemens 3VA1120-5GF46-0AA0 is a 4-pole SENTRON molded case circuit breaker (MCCB) rated 20 A continuous at 45 °C, with a TM240 thermal-magnetic release. It's built for line protection — the primary job is clearing faults fast in a distribution panel or motor control center. The interrupting ratings tell the story: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at 500 V or 690 V. That's serious SCCR headroom for high-fault utility feeds or transformer secondaries. The TM240 release has an adjustable li max of 320 A, so you can dial the magnetic trip to coordinate downstream.
Sizing and thermal derating
This breaker holds 20 A from 45 °C up to 55 °C without derating. At 60 °C it steps to 19 A, and holds that through 70 °C. That's a tight thermal curve — you lose only 5 % of capacity over the full operating range. The maximum power loss is 12 W, which is low for a 4-pole MCCB at this frame size. The insulation voltage is rated 800 V, and the max DC operational voltage is 600 V, so it's usable on DC bus applications within that limit.
Mounting and integration
Dimensions are 101.6 mm wide, 130 mm tall, 70 mm deep — a standard 4-pole MCCB footprint for panel mounting. The front face carries IP40 protection, so it's fine in a clean indoor enclosure but not for washdown zones. The N-conductor protection is rated 100 %, meaning the neutral pole is fully rated, not reduced. A motor drive option is available as an accessory for remote tripping or charging. No communication function onboard — this is a standalone breaker, not a smart metering device.