Doepke residual current circuit breakers (RCCB) disconnect the power supply when dangerously high fault currents occur, thus protecting people, animals, and installations. Devices from the DFS 4 series are compact four-pole residual current circuit breakers for single-phase or three-phase networks. In the standard version, they occupy only four division units. The all-current sensitive switches detect smooth direct fault currents as well as all other fault currents according to DIN VDE 0664-400. The HP (Heat Pump) variant has been specifically developed for the protection of heat pumps. The protection level of the all-current sensitive residual current circuit breaker meets all requirements of heat pump manufacturers. Additionally, the HP-optimized short-time delay ensures increased system availability. Standard version devices are designed for monitoring circuits with a rated voltage of 230 V, 400 V, and a rated frequency of 50 Hz. Features include: all-current sensitive for fault currents with frequencies and mixed frequencies from 0 Hz to 20 kHz; fire protection according to VDE 0100-420; full functionality with network voltages of at least 50 V AC on any two active conductors; high short-circuit resistance; double-deck terminals on both sides for large conductor cross-sections and rail connection; switching position indicator; multifunctional switch knob with three positions: on, off, triggered; neutral conductor position arbitrary; mounting type: quick fastening on mounting rail; installation position arbitrary; preferred feeding from above. Areas of application: RCCB of the HP variant are suitable for private, commercial, and industrial installations with TN-S, TT, and TN-C-S systems where heat pumps are used. Notes: suitable for use in 50 Hz AC networks; not suitable for use on the output side of controlled electrical devices.