What it is and what it does
The Siemens 3VA1125-5EF36-0AC0 is a SENTRON molded case circuit breaker (MCCB) for line protection, with a TM240 thermal-magnetic overcurrent release and a 25 A rated current at 40 °C ambient. It is a 3-pole device rated for an insulation voltage of 800 V and carries a maximum power loss of 8.5 W.
Interrupting capacity — the real-world fault rating
This MCCB provides interrupting capacities of 187 kA at 240 V AC, 121 kA at 415 V AC, 75.6 kA at 440 V AC, and 17 kA at both 500 V and 690 V AC. These figures define the maximum fault current the breaker can safely clear at each voltage level — critical for coordination studies and SCCR compliance in industrial switchboards.
Thermal derating — continuous current across temperature
Rated 25 A continuously at ambient temperatures up to 50 °C, the breaker derates to 24 A at 55–60 °C, and further to 23 A at 65–70 °C. This derating curve is essential when the breaker is installed inside a warm enclosure or near other heat sources — the effective ampacity drops before the trip unit reacts.
Physical fit and auxiliary configuration
The breaker measures 130 mm high, 76.2 mm wide, and 70 mm deep — a standard 3-pole MCCB footprint for panel mounting. It ships with two built-in auxiliary switches (HQ design) and the basic switch variant is 3VA11255EF360AA0. No undervoltage release, no ground-fault monitoring, and no communication function are included in this order code.