What this 250 A MCCB carries — and where the rating matters
The Siemens SENTRON 3VA1225-4GF42-0DH0 is a 4-pole molded case circuit breaker rated for continuous current at 250 A, with a TM240 thermal-magnetic overcurrent release. Breaking capacity is 121 kA at 240 V, 75.6 kA at 415 V, 25 kA at 440 V, and 11.9 kA at 690 V — so the available fault current at the panelboard determines which voltage column governs the install. Rated insulation voltage is 800 V.
Thermal derating and ambient temperature
The breaker holds full 250 A from 40 °C through 50 °C. Above that, derating is linear: 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 continuous current must be adjusted accordingly — no headroom for a 250 A load beyond that point.
Auxiliary contacts and undervoltage release
Factory-fitted with 2 auxiliary switches plus 1 trip alarm switch (HQ configuration), and an undervoltage release (UVR) as the auxiliary release. The UVR coil drops the breaker on loss of control voltage — standard for emergency-stop or undervoltage protection schemes. The integrated auxiliary trip order code is 3VA9608-0BB25.
Physical fit and panel integration
Dimensions: 158 mm height, 140 mm width, 70 mm depth. Front protection is IP40 — suitable for enclosed panel mounting where no water ingress is expected. The 4-pole footprint matches standard SENTRON 3VA frame spacing; verify busbar or lug kit compatibility with the existing distribution board.
N-conductor protection and mechanical endurance
N-conductor protection is rated at 100% — full-rated neutral pole, not reduced. Mechanical endurance is 15 000 operations, which suits frequent switching applications like capacitor bank or lighting control, not just infrequent fault protection.