RCD Devices (Residual Current Device or Safety Switches) are designed to minimize electrocution risk by instantly cutting off the Power in a dangerous situation before it can cause personal Injury.
How does an RCD work?
An RCD monitors the current flow in the active and neutral wires of the power lead or device connected to it, all the time looking for an imbalance or difference in the currents in each wire. For example if a path of lower resistance path is provided to earth… eg…personal contact with either active or neutral conductors providing a path to earth. The result of contact with one these wires causes a current imbalance and so the current going into a device is not equal the current exiting the device. At this moment the device trips and it does it instantaneously avoiding the full effect of Electrocution and personal injury, quite often it trips that quickly that little sensation is felt by the person who has inadvertently made contact with live conductors.
The momentary path provided to earth maybe an internal fault in an appliance or tool. This path and resultant imbalance may also occur by cutting the power cable or by using tools or appliances in unsafe, wet or damp areas. That is why,it is so important to get your RCD devices and their protected appliances tested and tagged thereby avoiding current faults and potential risks that will cause personal injury.
Safety Switch Types
There are two main safety switch types commonly in use: – Type 1 – used in medical, hospital or patient care situations and Type 2 in construction areas, workplaces and homes.
RCD Type Test Current Maximum Tripping Time
Type 1 10 mA AC 40 milli-seconds
Type 2 30 mA AC 300 milli-seconds
For Type 2 switches, if an imbalance of 30mA or more occurs, the RCD will trip – usually in less than 30 milli-seconds, but typically anywhere between 8 and 30 milli-seconds with a maximum test time of 300 mill-seconds.
The nominal tripping sensitivity for a Type 2 safety switch is 30mA; but from experience, the measured value is anywhere between 18.5 and 25mA.
If the safety switch or RCD tests properly without any appliances plugged into it, but trips each time an appliance is plugged in, then the appliance has an earth fault or excessive leakage current.
DO NOT BYPASS the SAFETY SWITCH – IT IS PROTECTING YOU FROM ELECTROCUTION.
RCD’s do not protect you from direct contact with both active and neutral wires in an electrical circuit, only the Live or Active (nominally Brown ) and Earth.
Usage Rules for Portable RCD’s
The RCD should be plugged directly into a power point and NOT an Extension Lead. The extension lead may be faulty and prevent the switch from operating in life threatening situations.
Do Not Use with any lead greater than 40 metres long. This can cause false tripping and frustration when no fault exists.
Test the RCD frequently and before each use to ensure proper operation.
Do not use any appliance or tool in a wet environment.
Do not immerse in any liquid or directly expose to rain.
If the RCD is dropped, do a push button test before using.
RCD’s are designed as safety devices – do not use them as On-Off switches.
THE BOTTOM LINE IS…
Electrical Appliances are designed to serve you but be careful it needs to be checked and maintained regular testing and tagging would help to avoid faults and future risk. Most importantly, the use of a safety switch is never a substitute for basic safety precautions.
Tested and True uses the very latest in Portable Appliance Testing…The STC ProLogger 2 it can perform RCD testing, Earth Leakage Detection and Run Testing all in one operation.On top this all our Technicians are Trained to National Standard UEENEEP008 by Intertag in Sydney NSW, all our Equipment is in good repair and in Calibration. Most of all we pride ourselves on our Knowledge of OH&S legislation and the current Australiand Standards ensuring that you get Quality Service at a competitive price.
Call Now Mobile 040 7605568
Visit us at
or our Newsletter http://testedtruenewsletter.blogspot.com/
Peter Hill Manager , Tested & True ~ test & tag Adelaide November 2009