'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