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.

Overvoltage will be detected – the PRCD-S+ switches off or cannot be switched on.

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)