What this MCCB is and what it does
The Siemens 3VA1150-3EF36-0DC0 is a SENTRON molded case circuit breaker (MCCB) — line protection version — rated for 50 A continuous current at 40 °C, with a TM240 thermal-magnetic trip unit that handles overloads and short-circuits without external power. Three-pole design switches all phases in a three-phase circuit. The TM240 release is a thermal-magnetic trip unit. Breaking capacity is 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 10.5 kA at 690 V — that covers most industrial service entrances and panelboard mains where fault current runs high.
Thermal derating — what the numbers mean for your panel
Rated 50 A from 40 °C through 50 °C ambient. At 55 °C it derates to 48 A, at 60 °C to 47 A, at 65 °C to 46 A, and at 70 °C to 45 A. If your panel runs hot — say a sealed enclosure near a furnace line — the 50 A nameplate doesn't hold; you need to account for the 48 A ceiling at 55 °C. Storage range is -40 °C to 80 °C; operating ambient is -25 °C to 70 °C. The -25 °C floor matters for unheated outdoor cabinets in cold climates — the breaker will still trip within spec down to that point.
Auxiliaries and releases — what's built in
Comes with an undervoltage release (UVR) as the auxiliary release type — design designation 3VA9608-0BB25. That means if control voltage drops, the breaker opens automatically. Useful for emergency-stop circuits or undervoltage protection on motor feeders. Two auxiliary switches HQ (high-quantity) are integrated — these give status feedback (open/closed/tripped) to a PLC or indicator lamp without needing an external contact block. No voltage trigger, no communication function, no phase failure detection, no ground fault monitoring. This is a straight thermal-magnetic breaker.
Footprint and panel fit
Dimensions: 130 mm height, 76.2 mm width, 70 mm depth. That's a standard SENTRON 3VA1 frame size — it fits the same mounting footprint as other 3VA1 breakers in the 50 A class. IP40 on the front — protected against tools and wires >1 mm, but not sealed against water. Mount inside a panel or enclosure; not for washdown areas.