Integrator note — 125 A fixed, 4-pole, line protection
The Siemens 3VA1225-5FF42-0CC0 is a SENTRON molded case circuit breaker (MCCB) built for line protection — fixed 125 A, 4-pole, no trip indicator. Breaking capacity scales with system voltage: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, 30 kA at 500 V, 17 kA at 690 V. That SCCR headroom covers most industrial distribution panels without needing a current-limiting fuse upstream. Rated insulation voltage 800 V. Power loss at full load is 59.5 W — factor that into enclosure thermal rise, especially in a multi-breaker panel with limited venting.
Thermal derating — continuous current vs ambient
Full 125 A holds through 50 °C ambient. Above that it steps down: 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, 223 A at 70 °C. Operating range is -25 °C to +70 °C; storage from -40 °C to +80 °C. If the panel sits near a heat source or in a non-conditioned enclosure, use the 55 °C or 60 °C column for sizing.
Integrated auxiliaries — what comes on the breaker
Factory-fitted with an undervoltage release (UVR) and two HQ auxiliary switches. The UVR trips the breaker when control voltage drops — common in emergency-stop circuits or undervoltage protection schemes. Two form-C aux switches provide status feedback to a PLC or annunciator panel without adding external blocks.
Dimensions and panel fit
Envelope: 158 mm height, 140 mm width, 70 mm depth. No communication function, no ground-fault monitoring. The supplied basic switch variant is 3VA12255FF420AA0 — that's the bare breaker core; this order code adds the UVR and aux switches in one configurable assembly.