The Siemens SENTRON 3VA9114-0RL20 is the RCD520 Basic residual current protection module Type A, designed as a load-side mounted accessory for the 3VA1 molded case circuit breaker family. It handles a rated operational current of 160 A at AC and accepts supply from either top or bottom infeed.
What the adjustable settings mean on the line
The residual current response value is selectable across seven steps from 0.03 A up to 5 A. That 0.03 A setting catches the 30 mA threshold required for personnel protection in most IEC 60364 installations, while the higher steps let you coordinate with downstream RCDs or tolerate leakage from VFD-fed motors without nuisance tripping. The non-tripping time is adjustable from 0 ms to 3000 ms in eight steps — use the delay settings for selective coordination (S-type behavior) so a fault on a branch clears before this main module trips.
Where this module fits in the panel
This is a Type A RCD, meaning it detects AC sinusoidal residual currents plus pulsating DC residual currents — the minimum for circuits with single-phase rectifiers, switching power supplies, or variable-speed drives. It mounts via screw fixing and connects to the main circuit through busbar connection, so it bolts directly to the 3VA1 breaker's load side without additional wiring.
Field-note: sealable and pre-alarm
The module is sealable — important for installations that require tamper-evidence after commissioning, common in utility or metering applications. It also provides a pre-alarm indication at 30% of the set residual current value, giving early warning before a trip event. That pre-alarm can feed into a monitoring system or just light a local indicator so maintenance catches a degrading insulation condition before it shuts the line.
Physical fit check
The 4-pole configuration covers three-phase-plus-neutral circuits.