Rated current and breaking capacity — the numbers that govern fit
The Siemens SENTRON 3VA1225-5GF42-0CA0 is a 4-pole molded case circuit breaker (MCCB) rated at 250 A continuous, with a TM240 thermal-magnetic overcurrent release. That 250 A rating holds flat from 40 °C through 50 °C ambient, then derates to 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, and 223 A at 70 °C — so in a warm panel you lose about 11 % of capacity at the top end. Breaking capacity is voltage-dependent: 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. For a 400 V class panel, the 121 kA figure at 415 V is the one that matters — it tells you this breaker handles high-fault-current scenarios typical of large distribution transformers or motor-control centers without cascading upstream.
Dimensions and panel integration
The breaker measures 158 mm high, 140 mm wide, and 70 mm deep. That 70 mm depth is the body only — allow additional clearance for the undervoltage release module and the outgoing cable lugs. The 140 mm width for a 4-pole frame is standard for this class; it occupies roughly the same footprint as other SENTRON 3VA fixed-thermal breakers in the 250 A range.
Undervoltage release and line protection design
This variant includes an undervoltage release (UVR) — the auxiliary release type is explicitly UVR, so the breaker trips when supply voltage drops below a set threshold. That is a common requirement for motor feeders where you want automatic disconnection on loss of control power. The product design is line protection, meaning the TM240 release curve is optimized for cable and busbar protection rather than motor or generator protection.
Power loss and thermal management
Maximum power loss is 59.5 W at rated current. That is the heat the breaker dumps into the enclosure — factor it into your panel thermal calculation, especially if the MCCB is mounted alongside other high-current devices in a sealed cabinet. The rated insulation voltage is 800 V, which covers 690 V line-to-line systems with margin.