Siemens 3VA1225-6GF42-0DH0 — 250 A SENTRON MCCB with TM240 Release
The Siemens 3VA1225-6GF42-0DH0 is a SENTRON molded case circuit breaker (MCCB) rated for 250 A continuous current at 40 °C, with a 4-pole configuration and a TM240 thermal-magnetic overcurrent release. Its interrupting capacity reaches 220 kA at 240 V and 154 kA at 415 V, which means it can safely clear high-fault currents in low-voltage distribution without cascading upstream — a key spec for main or tie-breaker positions where available fault current exceeds 100 kA. The TM240 release is a fixed thermal-magnetic trip unit, meaning the thermal element tracks the 250 A frame continuously, and the magnetic instantaneous pickup is factory-set. For line protection duty, this breaker does not include a voltage trigger, communication module, or phase-failure detection — it is a straightforward overcurrent-only device with an undervoltage release (UVR) fitted as standard. The auxiliary contact block is a 2-auxiliary-switch plus 1-trip-alarm-switch HQ variant (order code 3VA9608-0BB25 for the integrated auxiliary trip). The N-conductor protection is rated at 100 %, so the neutral pole is fully rated for the same current as the phase poles — important for 4-wire distribution where the neutral carries load current.
Thermal Derating and Ambient Conditions
The 250 A rating holds flat from 40 °C through 50 °C ambient. Above 50 °C the continuous current must be derated per the datasheet curve: 243.3 A at 55 °C, 236.5 A at 60 °C, 229 A at 65 °C, and 223 A at 70 °C. If the panel ambient runs above 50 °C, the breaker's effective capacity drops by roughly 11 % at the 70 °C ceiling — plan the load accordingly. Operating temperature range is -25 °C to 70 °C; storage range extends from -40 °C to 80 °C. The front face carries IP40 protection, so the breaker is suitable for enclosed panel mounting where no water ingress is expected on the operator interface.
Physical Fit and Panel Integration
Dimensions are 158 mm height, 140 mm width, and 70 mm depth. The 70 mm depth means the breaker protrudes less than 3 inches from the mounting surface — relevant when the panel door clearance is tight or when busbar connections are made on the rear. The 140 mm width is the standard 4-pole MCCB footprint for this frame size; verify the mounting hole pattern against the existing backplate or DIN-rail adapter if retrofitting.
Selectivity and Coordination Notes
With a rated insulation voltage of 800 V and interrupting capacities of 36 kA at 440 V and 17 kA at 690 V, this breaker can be applied in 400 V and 690 V systems, though the interrupting rating drops significantly at the higher voltage. For DC network applications, Siemens directs users to the 3VA MCCB device manual for switching power values — the standard AC ratings do not apply in DC circuits. The latching endurance is rated at 15,000 operations, which is typical for a fixed-mounted MCCB in distribution duty — not intended for frequent switching like a contactor, but adequate for infrequent manual isolation and automatic fault clearing over the breaker's service life.