Siemens SENTRON 3VA1050-4ED36-0JH0 — 50 A MCCB for Line Protection
That 121 kA at 240 V means it can safely interrupt a fault current up to that level without welding its contacts or cascading upstream — critical for high-fault panels near large transformers or service entrances. At 415 V the rating drops to 75.6 kA, at 440 V to 52.5 kA, and at 500 V or 690 V it holds at 11.9 kA. Rated insulation voltage is 800 V, so the breaker is suitable for 480/277 V and 600 V systems with headroom. Power loss at full load is 14.6 W — a figure to account for in enclosed panel thermal calculations.
Current Rating and Thermal Derating
The breaker carries a full 50 A from 40 °C up through 50 °C. At 55 °C it derates to 49 A, at 60 °C to 48 A, at 65 °C to 46 A, and at 70 °C to 45 A. If your panel ambient runs hot, size the continuous load against the derated value, not the 50 A nameplate. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The storage limit governs handling and warehousing, not running conditions.
Physical Fit and Auxiliary Options
The 3VA1050-4ED36-0JH0 measures 130 mm high, 76.2 mm wide, and 70 mm deep. That 70 mm depth is the dimension to check against enclosure depth and busbar clearance — it's shallower than many older MCCB frames, which helps in retrofit panels where gutter space is tight. It ships with a factory-installed auxiliary switch block: 2 auxiliary switches plus 1 trip alarm switch (HQ). A shunt trip release (STL) is also fitted. The trip indicator and voltage trigger are present, but undervoltage release and ground-fault monitoring are not included on this variant.