Electrical Earthing & Bonding

So what is the difference between Earthing and Bonding ?

Earthing and bonding have often been confused as being the same thing when in fact the two are quite distinct from each other.

Many electricians hear the term ‘earth bonding’ this essentially is a meaningless term that has somehow found its way into everyday vocabulary for some electricians. Trainee electricians are often rightly confused when they hear this term as of course earth bonding is technically incorrect.


So why do we earth and bond?

In basic terms, the idea of earth and bonding is to prevent electric shock.  Let’s use a kitchen as an example.  If a washing machine were to develop a fault, the current would travel down the earthing path.   Without the earth connection, the metal outer casing of the washing machine could become ‘live’.  The principal of earthing is to prevent this situation occurring, by limiting the duration of touch voltages.

Electrical Safety Plymouth

Bonding is a connection of all metallic parts using a protective bonding conductor.  So taking our faulty washing machine above, if you were to to touch it and then touch a metal tap in your kitchen, you would be the earth path and could receive a potentially life threatening electric shock.  The lack of bonding (as well as earthing) would create a chain effect of all metallic parts becoming live in the kitchen.  This would also include all pipework too.  It’s quite a scary scenario which is why earthing and bonding are so essential and why it is important to know the difference between the two.  Bonding is intended to limit the magnitude of touch voltages.

Earthing and bonding look very similar visually with each having green and yellow sleeving as identification.  However, both earthing and bonding must be carried out on an electrical installation to meet the safety requirements of BS7671.

Earthing and bonding is an essential requirement of every electrical installation, however it is often overlooked by an unqualified person attempting electrical work themselves.  This is just another reason to only employ a qualified 17th edition electrician or domestic installer to carry out electrical work.

How do I tell if my house has the correct earthing and bonding?

Electrical Earthing & Bonding PlymouthUnfortunately simply checking that the earthing and bonding is not enough. Only trained electrical installer can verify if the earthing and bonding is correct. This is because they will need to ensure the followjg three things:

That the earthing and bonding is actually there

That it is of the appropriate size

And finally that it has been correctly connected

As with most things related to electrical installation never assume and guess everything is fine just because it looks normal. If in doubt, give a professional electrician a shout.

See sizing of bonding conductors