Siemens SENTRON 3VA1225-5FF42-0AH0 — 125 A, 4-Pole Molded Case Circuit Breaker
The Siemens SENTRON 3VA1225-5FF42-0AH0 is a 4-pole molded case circuit breaker (MCCB) rated at 125 A continuous, carrying a TM240 thermal-magnetic release for line protection. Its 187 kA interrupting capacity at 240 VAC gives substantial fault-current headroom for high-available-fault installations, while the 800 V rated insulation voltage suits it for 480Y/277 V and 600 V delta systems where the breaker must withstand line-to-line potentials across open contacts.
Breaking Capacity Across Voltages
The interrupting rating drops with system voltage as expected: 187 kA at 240 VAC, 121 kA at 415 V, 75.6 kA at 440 V, 30 kA at 500 V, and 17 kA at 690 V. For a 480 V panel with a 65 kA available fault current, this breaker clears with margin; at 600 V the 30 kA rating still covers most industrial service-entrance conditions.
Thermal Derating and Power Loss
The TM240 release holds full 250 A rating up to 50 °C ambient (–), then derates linearly to 223 A at 70 °C. Maximum power dissipation is 57 W — relevant for enclosed panel heat calculations, especially when multiple breakers are ganged. The 70 mm depth and 140 mm width fit standard SENTRON mounting footprints; verify busbar and lug kit compatibility for the 125 A frame.