Electricity. A pretty great thing, no doubt, but it’s not without its dangers. An overloaded circuit or misdirected current has the potential to cause explosions, fires, and electrocution.
Engineers around 150 years ago found a way to reduce the risk of the first two of these bad things. It’s called a Fuse – essentially a thin section of wire designed to be the weak point in an electrical circuit. When a circuit’s current reaches a dangerous level, the fuse disintegrates and the path is broken. The fuse design has been updated endlessly over the past century, and has now largely been replaced by the Circuit Breaker, which offers similar features with the added benefits of being reusable.
These devices, however, rarely prevent electrocution – that is, death by electric shock. There are two common forms of electrocution:
- Fibrillation of the heart. Currents as low as 30mA (milliamps – 1 thousandth of an amp) may cause the heart to lose its ‘rhythm’ (arrhythmia) and result in cardiac arrest if not treated with a defibrillator.
- Burn or cell damage. Larger currents (over 1 amp) flowing through the body cause extreme heat, which is not something internal organs enjoy.
This is where the RCD (residual current device, also known as a Safety Switch) comes to save the day. By comparing incoming and outgoing current at the electrical switch board, the RCD can detect whether any current has been redirected through a second path – such as through a human body connected to ‘earth’ (I’ll explain this concept in a later blog post). The RCD will trip when a current differential of 30mA or more is detected, thus isolating the supply and hopefully saving the life of the involved person.
RCDs are now an established technology, with most ‘first world’ countries adopting the devices into their Wiring Standards.
Recent updates to the Australian Standards have necessitated the installation of RCDs to all new or modified power and lighting circuits in domestic buildings rated up to 20 amps, which includes nearly all household circuits.
If you would like to protect the members of your household by installing RCD protection, please get in touch. We would love to help!