Checking and improving earthing in your home

Any electrical appliance can develop a fault. If the insulation in a washing machine wears through, or a wire comes loose against the metal casing, that casing suddenly becomes live. If you touch the appliance, the current looks for a path to the ground, and the shortest path then runs through you. That is exactly what you want to prevent.

Earthing solves this by connecting the metal parts of your installation to an earth connection. If the casing becomes live, that current runs away via the earth conductor instead of through you. This escaping current is called leakage current or fault current. Earthing therefore makes sure the danger is carried away before it reaches you.

Earthing does not work on its own. It forms a team with the RCD in your fuse box. The RCD constantly measures whether any current is leaking away. As soon as a small difference arises between the outgoing and returning current, around 30 milliamps, it switches the circuit off within milliseconds. But that RCD can only work properly if the fault current has somewhere to go, and that is exactly what good earthing provides. If earthing is missing, the RCD often only switches off at the moment you touch the appliance, so far too late.

The age of your home says a lot. Houses built before the 1970s and 1980s were regularly laid out without complete earthing, or only in the places where it was required at the time, such as the bathroom and the kitchen. In the rest of the house you then find sockets without earthing contacts. Over the years installations have often been adapted bit by bit, which can make the picture messy: some circuits earthed, others not.

A visible signal is a socket without earthing contacts. On an earthed socket you see two metal strips or contacts at the sides, the earthing contacts. If they are missing, the socket is not earthed. Note: the reverse is no guarantee. A socket with earthing contacts can still be poorly earthed or not earthed at all if the earth conductor behind it is not properly connected. You cannot see that from the outside.

Other clues are an RCD that does not switch off when you press the test button, an old fuse box without an RCD, or slight tingles when you touch certain appliances. That last one is a serious warning sign: call an electrician and do not use the appliance until then. A renovation where old and new wiring run together is also a good reason to have the earthing checked properly.

You do not get certainty about your earthing with the naked eye, but with a measurement. A certified electrician measures the earth resistance: the resistance the current meets on its way from your installation to the ground. The lower that resistance, the better the fault current can run away and the faster the protection reacts. If the resistance is too high, the earthing works insufficiently, even if there appears to be an earth conductor present.

Alongside the earth resistance, the electrician checks whether every circuit and every socket is actually connected to the earthing, and whether the earth conductor runs through everywhere as it should. They test the RCD for operation and measure whether it switches off quickly enough. That builds a complete picture: not only whether there is earthing, but also whether it does what it should everywhere. This is a standard part of a NEN 1010 inspection of your installation.

With that picture you know where you stand. Sometimes the earthing turns out to be fine and there is nothing wrong. Sometimes it is missing in a few places and topping it up is enough. And sometimes the whole earthing arrangement is outdated and the installation deserves a more thorough approach. In all cases you get an honest verdict based on measured values, not on gut feeling.

Improvement starts at the source: a good earth connection with the ground. This is often done via an earth electrode or earth rod, a metal rod driven into the ground that connects the installation to the earth. In some homes the earthing runs via the water pipe, but with modern plastic pipes that is no longer reliable. An electrician looks at what the right and safest solution is in your situation and, afterwards, measures whether the earth resistance is now low enough.

From that earth point the earth conductor runs to the meter cabinet and from there to the circuits. If earthing is missing on certain sockets, the electrician tops up the earthing contacts: they run an earth wire to those points and connect them correctly. In an older home this sometimes means pulling extra wiring, which often coincides with replacing the fuse box or renovating the installation.

How extensive it is depends on what the measurement shows. Topping up a single socket is a small job. A home laid out entirely without earthing asks for more: a new earthing arrangement, earth conductors throughout the house and usually a modernised fuse box with RCDs. You get a clear price beforehand, so you know what it costs before anything happens.

There are cheap plug-in testers on sale that are supposed to indicate with a light whether a socket is earthed. They give a rough indication, but they do not measure the earth resistance and say nothing about the quality of the earthing. A socket can pass the test and still have too high an earth resistance, which means the protection is in reality too slow. Basing your safety on such a little tester is therefore not a good idea.

Work on the earthing itself is moreover work on the fixed installation, and under NEN 1010 that belongs with a certified professional. An earth conductor that is wrongly connected gives a false sense of safety: everything looks fine, until the moment it goes wrong. Precisely because earthing does its work invisibly, you want to be sure it is right. You only know that after a measurement by someone with the right equipment and knowledge.