The FDB2 RCBO unit is a multi-way housed earth fault protection system which shares DC immune technology with its smaller sister unit the FDB11. FDB2 offers 2 way, 3 way and 4 way options as standard with approval by Network Rail for use in DC electrified areas where it provides general purpose earth leakage protection, including overload and short circuit protection, for AC equipment without the problems of nuisance tripping associated with DC induced currents.

FDB2 units are modular, enabling expansion of multi-circuit installations with additional internal capacity or by connection of further units, so leading to useful cost and space savings at initial installation and over the lifetime of the project. Their development over 40 years use in this environment has led to their Network Rail approval for use with general service equipment, e.g. in cafes, adjacent offices etc. to protect against induced DC current.

Each surface mounting enclosure contains solid state electronics for stability and immunity from spurious tripping. Externally RCD test buttons and MCB toggles are fully accessible at the front panel of the enclosure.

Voltage 110/230V earth fault protection is offered at 20mA, 30mA or 100mA overload at 10A, 16A, 20A, 25A and 32A ratings.


The FDB2 is available from FDB Electrical at their online shop – Further information on FDB products and services may be found at: Find the latest information and news on the FDB blog –