The Siemens 3VA9214-0RL20 is a SENTRON RCD520 Basic residual current device (RCD) type A, designed as a load-side mounted accessory for the 3VA1 molded case circuit breaker family. It provides ground-fault protection for downstream circuits, with a rated operational current of 250 A at AC and a rated frequency of 60 Hz. The 250 A rating means this RCD is sized for the main feeder or large sub-feed in a distribution panel, not for branch circuits. It handles the full load current of a 250 A MCCB while adding adjustable residual current sensing.
Adjustable trip parameters — what they mean for coordination
The response value of the residual current is selectable from a set of fixed values: 0.03, 0.05, 0.1, 0.3, 0.5, 1, 3, and 5 A. The 0.03 A setting provides personnel protection; the higher settings up to 5 A allow selective coordination with downstream RCDs or equipment leakage. The set values of the limit value of non-tripping time are adjustable from 0 to 3.0 seconds in steps (0, 0.06, 0.15, 0.3, 0.5, 1.0, 2.0, 3.0 s). A delay of zero means instantaneous tripping; the longer delays permit selectivity with downstream devices by letting transient inrush or leakage pass without nuisance tripping. A pre-alarm indication at 30% of the set residual current value is integrated, giving early warning before the device trips. This is useful for planned maintenance rather than unplanned downtime.
The RCD520 mounts to the load side of a 3VA1 MCCB via busbar connection — it is not a standalone DIN-rail device. The infeed can be from the top or bottom, which simplifies panel layout when busbar routing requires flexibility. Dimensions are 140 mm width, 115 mm height, and 70 mm depth. The 140 mm width matches the 3VA1 four-pole MCCB footprint, so the assembly occupies the same panel space as the breaker alone. Screw fixing secures the module to the breaker. The module is sealable, which is required for installations where tamper-proofing the trip settings is mandated.