What this MCCB is and what it does
The Siemens SENTRON 3VA1125-6GD42-0AA0 is a 4-pole molded case circuit breaker (MCCB) rated for a continuous 25 A, fitted with a TM210 thermal-magnetic trip unit for line protection. It is designed for distribution and branch-circuit protection in commercial and industrial panels where high fault current capability is required. Its breaking capacity reaches 220 kA at 240 VAC, 154 kA at 415 VAC, and 121 kA at 440 VAC — figures that place it in the high-interrupting range for a 25 A frame, suitable for installations with large upstream transformers or high available fault current. At 500 VAC and 690 VAC the breaking capacity is 17 kA, so the voltage rating of the supply must be checked against the available fault current before specifying.
Thermal derating and panel fit
The breaker carries its full 25 A rating up to 50 °C ambient. At 55 °C it derates to 24 A, at 65 °C to 23 A, and at 70 °C to 23 A — a shallow curve that keeps most panel applications at the nameplate rating. Dimensions are 130 mm high, 101.6 mm wide, and 70 mm deep. The 101.6 mm width (4 inches) occupies four standard 25 mm pole spaces on a DIN rail or panel-mount footprint. Front IP40 protection covers the operator interface. Rated insulation voltage is 800 V, and maximum power loss at rated current is 8.5 W — a figure to include in enclosure thermal calculations.