Electrical earthing

Summary: Electrical earthing: Learn how to earth and bond earth wires to copper pipes.

Anything metal that comes into contact with electrical currents, such as appliances, wire terminals, radiators, or plumbing pipes, must be earthed to prevent electric shocks. If you install or re-wire any circuit or appliance you must ensure the green-and-yellow earth core is connected to the earth terminal in any switch, socket etc. This in turn should be connected to the main earthing terminal in the consumer unit or fuse box. If the earth core is bare, sleeve it with green and yellow insulating sheath. If there is no earth core in the circuit, choose an appliance or light fitting that is double-insulated.

Bathroom earthing

Because metal objects and plumbing pipes in a bathroom will be in close proximity to water as well as electricity, you must ensure that they are earthed. If you can touch an electrical appliance or switch at the same time as touching ANYTHING with metal on it, then the object or pipe must be connected to the main earthing cable. Objects like radiators, tap tails and airing cupboard pipes are easily forgotten - so be thorough.

You can either connect to the earth terminal in a socket, or to a pipe that has already been earthed and has an unbroken connection to the earth terminal in the consumer unit. If you connect to earthed pipes, make sure they are accessible to be inspected by making a hatch in the floor or panelling.

  • Cut off the power supply to the relevant circuit from the consumer unit.
  • Clean the pipe-section of any dust or paint to reveal bare metal
  • Use an approved earth clamp to attach to the pipes.
  • Screw the core of the earth cable into the clamp terminal.

An earth terminal block in the consumer unit.

Main bonding conductors must be connected to terminals on the earthing block and to gas, oil and water pipesn at the other.

Airing cupboard pipes should be linked to ensure an unbroken metal earth route.

Use 4mm2 earth cable to bridge metal pipe to metal pipe around a plastic water tank.

Link non-electrical metal fittings with 4mmearth cable. 

Author: C J Mills Google+