Safety for RCD protected circuits

Existing law states that if …any person who designs, manufactures, imports or supplies any article for use at work...to ensure, so far as is reasonably practicable, that the article is so designed ...’ . Adequate information, usually in the form of user instructions, is also required about what uses the article is designed for.

The operational leakage currents and residual currents produced by inverters will affect the prescribed operational characteristics of Type AC RCD used in the majority of UK Installations. This could lead directly to loss of life through electrocution and or fire.

The Types of RCD that can be safely installed upstream of the equipment, will depend on the specific design and components used in the machine. Equipment containing single phase or 3 phase inverters must not be connected to circuits protected by standard Type AC RCDs.

If this information is not provided in machine installation instructions, the electrician would have to provide Type B RCD protection, or refuse to connect the equipment; see BS7671 Reg 331.1.