Check the system for faulty connections, insulation faults or defective devices Pay attention to the frequency inverter’s functional residual currents (TI 800_000000003) A or AC residual current protective devices are not permissible as protective devices. If necessary, retrofit to an all-current sensitive B(+) RCD (e.g. Doepke DFS 4B SK) (TI 800_000000003). Please observe the relevant regulations and standards. In IT networks, the frequency inverter’s jumper or DIP switch used for the functioning must be plugged/switched to IT. This partly deactivates the integrated line filter and reduces residual currents. EMC interference can thus enter the network unfiltered. Observe the operating instructions of the frequency inverter.