Earth bonding

Main earth bonding

Main earth bonding conductors, coloured yellow and green, run from the earth terminal block in the consumer unit to the metal service pipes such as water, gas and oil. The size of these conductors is a minimum of 10mm sq.

Supplementary earth bonding

Different regulations may apply where plastic plumbing has been used. Please consult the Institute of Electrical Engineers Regulations for details, or seek the advice of a professionally qualified electrician.

There are strict rules on earthing of metal items in a house. Non electrical metal equipment, which could be a danger if it came into contact with electricity, including items such as radiators, pipes, sinks, basins, baths, towel rails etc. must be bonded to the earth connection terminal at the consumer unit. These include items which may not be immediately apparent such as metal frames supporting a plastic bath. These may be linked together and connected to the Earth terminal or separate earth cables may be used for each. The minimum size for this cable is 6mm sq. Earth cables have a green and yellow sleeve.

You can get the supllementary bonding tested by a professionally qualified electrician. Should anything fail these tests you must have them corrected.

In bathrooms, any metal item which you can touch must be bonded to the earthing system

Connection to each of these items is made by using an earth clamp or tag on the item. Metal sinks, for example, have an earthing tag pre fitted to them.

Clamps, used to earth metal pipes, consist of a strap which is fastened around the pipe and a terminal to which the earth wire is connected.

The effectiveness of the connection is vital. So, if you are not certain how this should be carried out or have not done it before, have the work done by a professional and get them to show you how it is done. A common error is to fit an earth clamp to pipework without cleaning away oxidation or paint from the surface first. The result of this is that there may not be a good bond between the two. Positive contact between the pieces is essential. Any earth bonding carried out should be inspected by a qualified professional.

Pipes either side of plastic items such as water tanks or plastic fittings may need to be bridged to maintain earth continuity. An earth clamp is fitted to the pipe on either side and an earth conductor is run between them.

• Electrics safety