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RCDs - Type-B

'B' type RCDs in addition to normal AC, can detect high frequency AC and pure DC earth leakage currents.  Reducing the risk of fire and/or electrocution through automatic disconnection of the electrical supply relies on the selection of the correct type of RCD.  These 2P and 4P (all casings are 4 module width) devices range from 16A to 125A in standard sensitivity ranges of 30mA, 100mA and 300mA.

Each unit has a contact position indicator, in addition to a reset position, which shows whether the device has been switched off manually or tripped due to a fault. The devices accept both pin and fork busbar, the pin terminal having a maximum cross-section of 50mm. These RCDs also have a facility to accept a circuit identification label behind a clear plastic window on the front of the unit.

Applications requiring 'B' types include:

  • PV installations
  • Frequency converters
  • UPS installations
  • High-frequency power converters
  • Building site power supply cabinets

Specifically related to grid-tied Solar PV installations, and especially with the growth in use of TL (Transformerless) inverters, the correct selection and use of a B Type RCD is imperative to ensure proper and adequate protection of the AC circuit and PV system.

These Doepke B Type RCDs are available in 3 different types (NK, B+ and SK), depending on the characteristics of the installation environment and equipment being used.  A useful selection guide can be downloaded from the links below to aid the selection process. 

Doepke Type-B RCDs

Residual Currents in PV Installations

Doepke RCD Selection