Rated current and breaking capacity
The Siemens SENTRON 3VA1225-5FF42-0CA0 is a 4-pole molded case circuit breaker rated at 125 A continuous, with a TM240 thermal-magnetic release designed for line protection. Its breaking capacity steps with system voltage: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, 30 kA at 500 V, and 17 kA at 690 V — so the available fault current at the panel's service entrance determines which voltage column governs the selection.
Thermal derating and power loss
The breaker holds its full 125 A rating up to 50 °C ambient. Above that, derating is gradual: 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, and 223 A at 70 °C. Maximum power loss is 59.5 W — a figure to budget for in enclosed panels where heat rise stacks across multiple devices.
Undervoltage release and auxiliary options
This variant includes an undervoltage release (UVR) as the auxiliary release type — the coil drops the breaker if control voltage falls below the dropout threshold, a standard requirement for emergency-stop and safety isolation circuits. The base switch is 3VA12255FF420AA0; no communication function or ground-fault monitoring is fitted on this order code.
Dimensions and panel fit
Physical footprint is 140 mm wide by 158 mm tall by 70 mm deep. The 70 mm depth is the dimension that matters for enclosure depth clearance — standard 200 mm deep enclosures leave ample room for wiring gutters behind the breaker.
Environmental and insulation ratings
Rated insulation voltage is 800 V. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The storage minimum of -40 °C covers cold warehouse or unheated site storage before installation.