Prüftaste

Prüftaste is a term used in German for a dedicated pushbutton found on electrical protective devices that allows a user to test the proper operation of the device, most commonly a residual current device (RCD), also known as a Fehlerstromschutzschalter. The button is typically labeled “Test” and is a standard feature on many protective devices installed in power installations.

Operation: When the power is supplied, pressing the Prüftaste subjects the device to an artificial fault condition by creating a deliberate current imbalance between live and neutral, usually via an internal resistor or switching element. This imbalance should cause the protective mechanism to interrupt the circuit within the device’s specified trip time. After tripping, the device is reset manually.

Purpose and standards: The Prüftaste verifies the functional capability of the protective device to trip in response to fault conditions. It does not replace external fault simulation and does not test insulation quality or real-world fault scenarios. The test function is standardized for RCDs (IEC 61008, IEC 61009) and is addressed by national regulations such as DIN VDE 0100 in Germany; manufacturers provide guidance on recommended test intervals.

Usage notes: Use the Prüftaste at intervals prescribed by the device manufacturer (often every six months) and after any electrical work. If pressing the button does not trip, the device may be faulty and should be inspected by a qualified electrician. The test should not be relied upon during critical operations.

Terminology: The term is formed from prüfen (to test) and Taste (button).