Functional earth is the earthing of a point or points in a system or an installation or in equipment for purposes other than safety, such as for proper functioning of electrical equipment.

This is also known as isolated earthing or clean earthing or noiseless earthing or separate earth.

In home wiring it would only be required where there was equipment that required functional earthing for it’s operation. The connection of any functional earthing should be made to the installations Main Earth Terminal and be clearly labelled as to its purpose.