Line protection MCCB with thermal-magnetic release
The Siemens SENTRON 3VA1112-3EF32-0HC0 is a 3-pole molded case circuit breaker (MCCB) rated for 125 A continuous current, fitted with a TM240 thermal-magnetic overcurrent release. The TM240 release provides fixed thermal and magnetic trip settings for line protection — it is not user-adjustable, so the coordination study must be locked in before the breaker is panel-mounted. The part carries a rated insulation voltage of 800 V and delivers interrupting capacities of 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 10.5 kA at 690 V, which covers most low-voltage distribution fault levels without cascading upstream.
Thermal derating and panel integration
At 40 °C, 45 °C, and 50 °C the breaker holds its full 125 A rating. Above 50 °C the continuous current must be derated: 120 A at 55 °C, 117.5 A at 60 °C, 115 A at 65 °C, and 112.5 A at 70 °C. The operating temperature range is -25 °C to 70 °C. The enclosure depth is 70 mm, width 76.2 mm, height 130 mm — fits standard SENTRON panel cutouts. Front protection is IP40, adequate for enclosed distribution boards but not for washdown zones.
Auxiliary contacts and shunt trip provision
This version ships with 2 HQ auxiliary switches (form C) pre-installed, part of the integrated auxiliary trip assembly (order code 3VA9688-0BL30). A shunt trip release (STL) is included for remote tripping; undervoltage release, phase failure detection, and communication functions are not present on this variant. The latching endurance is rated for 15 000 operations, which is the mechanical life before contact wear becomes a consideration for the auxiliary circuit.