What it is and what it does
The Siemens 3VA1112-3EF36-0HH0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in commercial and industrial distribution panels. Its 125 A continuous current rating at 40 °C (derated to 114 A at 70 °C) covers feeder and main-switch duty for moderate-load subpanels, motor control centers, and building services. The interrupting capacity is voltage-dependent: 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 11.9 kA at both 500 V and 690 V. That means this breaker can clear high-fault scenarios on the secondary side of a 240/415 V transformer without cascading upstream — the 75.6 kA figure at 240 V is the one to check against your available fault current for 240 V delta or 208Y/120 V services. Rated insulation voltage is 800 V, so the breaker is suitable for 690 V line-to-line systems with margin. The 3-pole construction handles three-phase loads; the unit ships with a shunt trip (STL) release and a complement of 2 auxiliary switches plus 1 trip alarm switch (HQ), giving the controls integrator both status feedback and remote-trip capability without adding external relay logic.
Thermal derating and power loss
The breaker holds its full 125 A rating from 40 °C up to 50 °C, then derates linearly to 114 A at 70 °C. For a panel that runs warm — say 55 °C inside the enclosure — you still get 122 A continuous, which is often enough to cover a 100 A feeder without upsizing the frame. Maximum power loss at rated current is 28.1 W, a figure to include in your enclosure thermal budget if the breaker is in a sealed, non-ventilated cabinet.
Physical fit and panel integration
Dimensions: 130 mm high, 76.2 mm wide, 70 mm deep. Width is 3 in, depth 2.76 in.