How does PCE’s PRCD-S+ work?

After plugging in the PRCD-S+ into a socket outlet with unknown function and safety protection, an automatic check is performed. If everything is correct, the LED signal starts blinking GREEN after about 1-2 seconds.


To switch ON please push and hold the button shortly. The LED signal stays GREEN. The PRCD-S+ is now ready and on the output side an electrical appliance can be used.

During every switch-ON routine, a very little testing current is applied to the electrical conducting ON button. Thereby a check is performed, whether the testing current can be diverted through earth (this means through the human body). If this is not the case (for example by wearing a glove) the PRCD-S+ is not able to switch on (= LED signal indicator blinks red).  After resetting, the switch-ON routine can be repeated without wearing a glove or a different position of the location.


The ON/OFF button of the PRCD-S+ works additionally as a sensor surface to check the potential of the user against ground (PE). If there is a potential difference, a very little current is diverted  through the user and the sensor button into the power line. At a voltage difference of 230V this failure current is less than 0,5 µA effective. The treshold value of this potential difference, where a switching ON of the PRCD-S+ is  prevented, is typically between 30 and 40 Volt.
Such a test is performed every time during switching-ON routine of the PRCD-S+ at the push on the button. If this testing current is not diverted torwards ground potential, the unit recognises it as a failure current and prevents switching ON. This for example happens, if the switching-ON of the PRCD-S+ is tried with an isolating glove or any other isolating object.

After putting an electrical load into operation, the PRCD-S+  works as a regular residual current device (RCD) with a release current of 30mA. It prevents users against dangerous failure currents, which can be caused by defective electrical devices.

The integral undervoltage trip prevents automatic restarting of the PRCD-S+ after a power failure or an interruption in the power supply.

An additional protection, and therefore a safety against secondary accidents is been given.

The integral surge voltage protection detects 400 VAC and 220 VDC and does not allow these to pass (a weak point occurs).

The PE conductor circuit is switched on in advance and switched off with a delay.
Failure situations like “external voltage on PE or exceeding of the failure current” will cause an interruption of L and N conductor. The PE conductor circuit  will remain closed and the PE potential remains monitored!

Press the button on the PRCD-S+ briefly, until the LED signal unit flashes GREEN. All poles (conductors) of the PRCD-S+ are now switched off.

The PRCD-S+ is to be used as:
portable residual current device with rated residual current IΔn ≤ 30 mA for alternating current, pulsating DC residual currents and phase capped fault currents.

The PRCD-S+  is not to be used as:

  • Refrigeration devices or similar applications (no automatic switching on after a power failure)
  • Machines with high inrush currents
  • IT-power systems (isolation transformers, power generators, etc.)

For the correct functioning of the PRCD-S+ device, the presence of a protective conductor is imperative.

Rated voltage: 230V~
Rated frequency: 50Hz
Rated current: 16A
PE conductor circuit is switched on in advance and switched off with a delay
Rated residual current : 30mA
Ambient temperature: -25°C bis +45°C
Connection cross-section: 1−2,5mm²
Cable dismantling length: 35mm  /  wire stripping length: 7mm
Cable diameter: Ø 10–14mm
Standards/code DIN VDE 0661 and DGUV Information 203-006 (former BGI/GUV-I 608)