MCCB for distribution panels — 20 A, 3-pole, line protection
The Siemens 3VA1120-4EF32-0AH0 is a SENTRON molded case circuit breaker (MCCB) rated for 20 A continuous current at 40 °C, with three poles and a TM240 thermal-magnetic release for line protection — no undervoltage release, no ground-fault monitoring, no communication module. It carries 121 kA breaking capacity at 240 V and 75.6 kA at 415 V, so it handles high-fault utility feeds in distribution switchboards without cascading upstream. The auxiliary contact set includes two auxiliary switches plus one trip alarm switch (HQ type), giving the panel PLC or BMS a positive open/closed/tripped status on each phase.
Thermal derating and ambient limits
The 20 A rating holds flat from 40 °C through 50 °C; above that it derates linearly to 18 A at 70 °C. That matters for a panel near a furnace line or in a hot electrical room — at 55 °C you lose 0.8 A, at 60 °C you lose 1.2 A, at 65 °C you lose 1.6 A. The operating range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The front face carries IP40 protection, adequate for a closed cabinet but not for washdown zones.
Mechanical fit and panel integration
Dimensions are 130 mm high, 76.2 mm wide, 70 mm deep — a standard 3-pole MCCB footprint that drops into most DIN-rail or panel-mount distribution boards without re-drilling. The 15 000-cycle mechanical endurance is typical for a fixed-mount MCCB in a distribution role; it is not a switching device for frequent motor starts.