Line protection MCCB — 125 A, 4-pole, TM240 release
The Siemens 3VA1112-3FF42-0AA0 is a SENTRON molded case circuit breaker (MCCB) configured for line protection in a 4-pole form factor. It carries a continuous current rating Iu of 125 A at 40 °C, with a TM240 thermal-magnetic release that provides overload and short-circuit protection for distribution feeders, panelboards, and downstream branch circuits. The 4-pole construction suits three-phase systems with a fully rated neutral — common in IT or TN-S networks where the neutral requires overcurrent protection. Breaking capacity is published across five voltage levels: 76 kA at 240 V AC, 53 kA at 415 V AC, 32 kA at 440 V AC, and 11.9 kA at both 500 V and 690 V AC. These figures define the maximum fault current the breaker can safely interrupt at the given system voltage — critical for verifying selectivity and SCCR compliance in the panel schedule. Rated insulation voltage Ui is 800 V, and the maximum rated operational voltage for DC circuits is 600 V. The front face carries IP40 protection — suitable for installation inside a switchboard or enclosure where the breaker is not exposed to dripping water or dust ingress.
Thermal derating and panel integration
Current-carrying capacity is temperature-dependent across the operating range. At 40 °C, 45 °C, and 50 °C the breaker holds 125 A without derating. Above 50 °C the rating steps down: 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, and 114 A at 70 °C. Plan the enclosure ventilation and busbar sizing around the actual ambient temperature inside the panel — a 70 °C internal ambient reduces available current by nearly 9 % from the 125 A base. Physical footprint is 101.6 mm wide, 130 mm tall, and 70 mm deep — a 4-pole MCCB that fits standard Siemens SENTRON mounting accessories and busbar systems. The N-conductor protection is set at 50 % of the phase rating, a common configuration for distribution boards where the neutral is sized smaller than the phases. Maximum power loss is 28.1 W. This figure drives the heat load inside the enclosure for thermal calculations, particularly in multi-breaker panels where cumulative losses affect the internal ambient temperature.
Lifecycle and sourcing posture
Operating temperature range spans -25 °C to +70 °C; storage range extends from -40 °C to +80 °C. The part carries an optional motor drive extension (Product Extension / Optional / Motor Drive = Yes), enabling remote motorized operation for integration into automated power-management systems — relevant for vessel automation and bridge-integrated switchgear where remote tripping and reset are required.