The Siemens SENTRON 3VA1120-5EF36-0AH0 is a 3-pole molded case circuit breaker (MCCB) rated 20 A at 40 °C with a TM240 thermal-magnetic release. Its interrupting rating hits 187 kA at 240 V — that's the short-circuit current it can safely clear without welding contacts or rupturing the case. For a 20 A frame, that's an unusually high breaking capacity, meaning it can sit close to a high-fault transformer or busway without needing a current-limiting upstream device. The 3VA1120-5EF36-0AH0 is designed for line protection — feeding distribution panels, motor control centers, or branch circuits where a 20 A feed with high available fault current is expected. It carries 2 auxiliary switches plus a trip alarm switch HQ, so it can signal its state back to a PLC or SCADA without an add-on module.
Panel fit and mounting
The 3VA1120-5EF36-0AH0 measures 76.2 mm wide, 130 mm tall, and 70 mm deep. It mounts on a DIN rail or bolts directly into a panel backplate. The 70 mm depth is shallow enough to fit a standard 200 mm deep enclosure with clearance for rear-connected busbars. The 76.2 mm width (3 inches) is the standard 3-pole MCCB footprint — it occupies three 25.4 mm module positions on the rail.
Ratings and derating
Rated current holds at 20 A from 40 °C up to 55 °C ambient, then derates to 19 A at 60 °C through 70 °C. That's a flat thermal curve — no derating step until 60 °C, which is unusual for a compact MCCB. The insulation voltage is rated 800 V, and the breaking capacity drops from 187 kA at 240 V to 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at 500 V and 690 V. Maximum power loss is 12 W.