What this MCCB is and what it carries
The Siemens 3VA1112-5EF36-0AD0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection — the primary feeder or main distribution breaker in a panel, not a motor-protective device. It carries a TM240 thermal-magnetic release, meaning the thermal element is fixed at 240 A frame rating with adjustable magnetic pickup; the breaker itself is rated 125 A continuous at 40 °C ambient, and that current holds flat up to 50 °C before the thermal derating curve begins (122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, 114 A at 70 °C). For a panel builder, that means you can load it to 125 A in a ventilated enclosure without worrying about nuisance tripping until the ambient climbs past 50 °C. Breaking capacity is where this part earns its place in high-fault installations: 187 kA at 240 V AC, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at both 500 V and 690 V. Those numbers are symmetrical RMS values, so the breaker can interrupt a bolted fault at those levels without welding contacts or venting plasma — critical for series-rated panels where the MCCB must clear a downstream fault the branch breaker cannot. The 800 V rated insulation voltage (Ui) confirms it is built for 690 V line-to-line systems with margin.
Physical fit and panel integration
Three-pole, 76.2 mm wide (3 inches), 130 mm tall, 70 mm deep. That width is a standard MCCB footprint for 125 A class — it occupies three 25.4 mm pole spaces on a DIN rail or bolts directly to a mounting plate. Depth of 70 mm means it clears most 200 mm deep enclosures with room for rear-connected busbars. The breaker ships without an undervoltage release or shunt trip (no voltage trigger, no trip indicator), so if the spec calls for remote tripping, you add the 3VA auxiliary switch block — the design accepts up to three auxiliary switches HQ.
Power loss and thermal management
Maximum power loss is 28.1 W at rated current. In a sealed, non-ventilated enclosure with multiple breakers, that heat adds to the internal temperature rise — factor it into your thermal calculation if the panel ambient approaches the 70 °C operating maximum. Storage range is -40 °C to 80 °C, so the breaker can sit in an unheated warehouse or a hot shipping container without damage.