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Earthing and Grounding of Electrical Circuits

Electrocution, electric shocks and earthing of electrical circuits

Earthing (sometimes known as grounding) of electrical circuits is a very important safety measure for any building. Here we explain what earthing is, how important it is and how we earth the electrical circuits in a building using an earthing rod and how we check if it works correctly.

For safety any building with electrical circuits needs to be "earthed" or "grounded"

As I have said before the most important aspect of any building is its structure.

After the structure the next most important thing is its earthing or grounding - a metal rod pushed into the ground. I am referring to a simple yet largely unheard of device whose purpose is to prevent that immortality removing snap, crackle and pop that leaves your face blackened, your hair singed off and an unplanned appointment with your maker. I am, of course, talking about an earthing or grounding rod.

Recently we talked about testing your electrical circuits and the tendency for those naughty little electrons to confuse your heart and your brain while cooking your inner parts. Rather like a dog that cocks its leg against the sofa, naughty electrons need to be put outside if they get out of hand. To do this we bury them in the garden, we send them to earth. They don't mind, in fact they love dashing off to mother earth which is so gihuge that a few recalcitrant electrons can be easily absorbed without even being noticed.

Any building with electrical circuits needs to be "earthed" or "grounded" to carry loose electricity away.

Earthing or grounding system in a building

I'll try and keep this simple so even neuro surgeons can understand it. If you plug in your television or anything else for that matter you put a plug into a socket. For reasons we will not pursue at this stage because it may contravene the anti pornography bill, the plug is the male part and the socket is the female part. Have a look at the male part and you will find an electrical plug has 3 pins - except in Indonesia (confused already? Never mind). In Indonesia plugs have 2 round pins but they also have 2 contacts on the sides of the plug which you will note engage with two spring clips in the sides of the socket. If there are no contacts on the sides of the plug ‐ there is no earth connection.

The 2 round pins are the connectors of the live and neutral connections which allow those useful but awkward little electrons to pass into and out of your device, whatever it may be, to give it power. If something goes wrong we need to let those electrons go into the garden so we have the spring connectors which connect the metal body of your appliance to the earth.

Look in any modern electrical wiring and the yellow and green striped wires should be the earth connections.

The earth connections from your plug sockets connect back to your main electrical distribution box. Here all the yellow and green striped wires from the plug sockets around your house are connected to a copper earth or grounding cable which goes outside and is literally buried in the garden.

"Ah but", I hear you say, "my television, laptop, electric toothbrush and nasal hair remover have small plugs with only 2 pins and no spring clips". Yes I know, this is because they don't need an earth, the appliances have plastic covers which prevent inquisitive little fingers from getting anywhere near electrical parts. Back in the days when most electrical goods had steel cabinets an electrical fault could cause the cabinet to become "live" (infested by excited electrons) and people who touched the cabinet might find themselves in an ongoing negative survival situation.

The rule is that anything with a steel case such as a washing machine, tumble drier, refrigerator, desktop computer, iron, toaster, etc. should have an earth connector. Under normal circumstances lighting circuits do not have earth connections.

A word of caution. Plug boards, those things with a cable and row of sockets we use to plug many things into a single plug socket, usually do not have adequate earth connections. If you have a look inside you will often find that even ones that appear to be of good quality and have earth spring clips in the sockets do not have the earths connected inside.

How to earth electrical circuits

To earth electrical circuits we use an earthing or grounding rod to send them to earth.

An earthing rod (elektrode bumi in Indonesian) is a copper rod, usually about 10 millimetres diameter that is pushed deep into the ground where it can safely release the electrons. The rod needs to be about 4 metres long and should be pushed into solid earth. If the earth has been disturbed and so is not compacted the electrical connection might not be good enough.

The earth or grounding cable that connects from your distribution panel to the earth rod is a bare copper cable normally around 25 square millimetres in cross sectional area which is connected to the top of the rod with a copper clamp (electrons simply love copper).

Many electrical panels on domestic installations in Indonesia do not have adequate earthing connections. This is because the vast majority of "electricians" do not have any formal training. Knowledge (or a lack of it) is passed on from one misguided soul to another. Unfortunately the importance of earthing electrical systems and the standards that are required to make circuits safe are not widely understood. Many electrical panels have only a single 3mm diameter copper wire to connect to earth (this is not large enough) while many others have no wire at all.

If we start to look at larger installations that use 3 phase electrical systems (and many large villas do have 3 phase systems) earthing connections are more complex and installations can be worse with electrical contractors using dodgy methods to save money. It is all a bit too complicated to go into here.

How to check earth connections?

To check earth connections we use an earth meter. This is a very sensitive meter that measures how easily those little electrons can flow to earth. We measure the resistance of the earth connection. We talked about ohms and resistance a few weeks ago. We need the resistance to be very small, for technical people about .02 of an ohm (that's smaller than an ant's tonsils) is good.

Obviously the ground varies a lot and the ability for the electricity to flow to earth is affected by the type of ground we are on. Wet clay is usually very good while dry rocky ground may be more challenging. Pushing an earthing rod into solid rock is obviously somewhat problematical to say the least. In such cases we use an earthing plate. This is usually a 1 metre by 1metre square of copper plated steel which is buried in the ground.

There are one or two tricks to improve earthing connections. I met an old electrician who really knew his stuff who swore by using a mixture of cow dung and banana pulp around the earthing rod (it was probably the smell that made him swear). The mixture helps to improve the electrical conductivity of the earth.

Earthing and the Electrical Standard.

Correct earthing is fully covered in the Indonesian electrical standard SNI 04-0225-2000 (commonly known as PUIL 2000) which is based on and matches world electrical standards. This standard, unlike many other standards, is legally binding. All systems are supposed to comply. Most house fires in this country are put down to faulty electrical circuits so this is very relevant from an insurance point of view.

Copyright © Phil Wilson October 2013
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