How safe are you when using Electricity
in your home or workplace?
If your premises has a Residual Current Device, or RCD, you are much safer then generations before you, thanks to the mines in South Africa.
The primitive form of our modern day RCD, originated in South Africa where electrocution was commonplace in the mining industry.
RCD’s have come a long way and are now required in all new installations. There are now regulations for a minimum number of RCD’s in an installation as well. In fact as soon as you modify a circuit that does not have RCD protection, you are required by law to install one.
An RCD (sometimes referred to as earth leakage) is a device that not only breaks the circuit on the active (red cable going ‘out’ to each light or power point) but it also breaks the circuit on the neutral (black cable coming back from the appliance) which is a much safer combination than just a circuit breaker. It will also limit the current and time exposed to lethal current before it does any major damage.
There was a popular misconception in years gone by that you could not be electrocuted by the neutral (return cable). This couldn’t be further from the truth.
If you do get electrocuted via a neutral, the safety equipment on the circuit will take longer to activate, if at all.
There are also many situations where you can have a dead short between both active and neutral and older circuit breakers do not trip at all. Scary thought.
How does an RCD keep me safe?
The RCD works on the premise that current flowing to an appliance (light PowerPoint etc) should equal the return current also.
When there is a fault situation the RCD senses the difference in potential between either the active or neutral and the RCD switches off the circuit within .04 of a second and before the amperage reaches 30mA(depending on installation and required spec).
The earth leakage could be through current going down to earth either due to a damaged cable or power tool or if you have inadvertently come into contact with live conductors or parts.
For example, the lass in the picture above is using a faulty hair drier and comes into contact with an earth point from the tap which creates a circuit to earth with a lower resistance than the actual power circuit from the switchboard to the hair drier. This is earth leakage and without an RCD it can be fatal.
If you have children that are young and getting into all manner of things, or pets that like to chew, I recommend you replace that old fuse board and install a new switchboard with RCD protection for both power and lights.
At the very least, please get us to install some external RCD’s for those power circuits.
I like to think the RCD saved Mouse, our wolfhound X mastiff, not more than two months ago when he chewed through a live power cord.
To create a safe household or business and to protect your family, friends or clients:
- Avoid faulty power tools or appliances
- Install RCD’s or upgrade that old switchboard
- Don’t overload power circuits
- And DON’T DIY!
Call a licensed electrician because that’s what we are here for.
And if you are in business? AS/NZS 3760 requires testing of RCD’s in commercial workplaces on a regular basis with results recorded for time and trip current. RCD’s are for the safety of you and your employees and clients.
By Jon Story