That 400 A rating holds through 50 °C — only above 55 °C does it derate, stepping down to 375 A at 55 °C and 300 A at 70 °C, so panel builders can size this breaker into a warm enclosure without losing headroom. Breaking capacity is 187 kA at 240 V, 121 kA at 415 V and 440 V, and 75.6 kA at 500 V — figures that cover high-fault utility feeds and large motor control centers. The 4-pole design with ground-fault monitoring via summation current formation on L+N conductors means this unit can serve as the main disconnect for a solidly-grounded wye system where ground-fault protection is required.
The 3VA2340-5JQ42-0AG0 occupies 184 mm width, 248 mm height, and 110 mm depth on the panel. The 184 mm width for a 4-pole frame is standard for this class; verify the backplate cutout matches the Siemens 3VA mounting pattern if replacing an older 3WL or 3VF frame.