The second in our new series designed to explain the ins and outs of electrical safety focuses on earthing, a fundamental component of any installation.
So what exactly is the earth wire, and what is its role? In effect, the earth wire will connect your switches, sockets and other appliances back to where your consumer unit – or fuse box – is located. In turn, this will be connected to a mass of ground or earth in the vicinity of your property. You will also see an earth wire in every Class 1 (requires an earth) plug, and it’s easily identifiable with its distinctive green and yellow casing. Class 2 appliances do not require an earth in the plug.
The main purpose of connecting the supply to earth is to ensure that should a fault occur the electrical current is channelled down the earth wire to cause the fuse to blow or the circuit breaker to disconnect the supply. If you think of lightning, electricity will always seek to find its way to ground. As a result, the route to earth should always be of lower resistance than other paths that may be opened up by a fault, for example through a person’s feet where they’re standing.
Lightning can be spectacular, and the effect is created when the electricity in the sky finds its way to earth as that’s the path of least resistance, and your electricity is no different.
In terms of what needs earthing, this will include any parts of your electrical installation – such as a light switch or a kitchen appliance case – that are made of a conductive part, ie metal. In the event of a fault, these will become ‘live’ unless they’re earthed and will likely cause an electric shock. In the case of a metal light switch, for example, it’s not unheard of for a wire to work its way loose, come into contact with the metal front plate and shock anyone who switches the light on or off. If the switch is correctly earthed, however, the protective breaker will blow and the supply will be disconnected, thus preventing a shock.
Fixed wire testing carried by registered and competent electricians such as ourselves can ensure that your property – and everyone who lives in and/or uses it can do so safely.
MS Electrical offers PAT testing and fixed wire testing in Cambridge. Please call us on 01223 850301 or complete our enquiry form to request a no-obligation quotation.