RCD stands for Residual Current Device. They are also know as saftey switches. They are required by law in all homes and work places. RCD’s are mostly found in meter boxes but are also available in portable configurations. Some devices have a built-in RCD. It is becoming more common for portable devices such as floor polishers and pressure cleaners to come supplied with an RCD.Fixed RCD
Simply, an RCD measures the current that flows to and from an appliance and detects if there is any difference between the flows. If the RCD detects that there is a difference (meaning that current is leaking somewhere) it triggers and shuts off both the active and neutral wires.
There are two common types. Type I that has a trip rating of 10mA and Type II thta thas a trip rating of 30mA. In addition to the trip rating, the RCD is required to trip within a defined time period. Type I RCD’s are generally used for patient areas of hospitals, dental practices etc. Type II RCD’s are found in industry and domestic homes. The standard, AS/NZS 3760:2010 requires that a type II RCD should trip within 300mS (.3 of a second) In practice, they trip much faster than this. How would you know if an RCD was faulty?
When testing a fixed RCD, a portable appliance tester will simulate an earth leak appropriate to the type of RCD being tested and meaures the time it takes for the RCD to react. This is done twice on each RCD for 0 and 180 degrees of the current phase. If passed, the final test is a simple push button test to ensure that the manual test mechanism is also working correctly. All of the results are stored in the portable appliance tester and form part of your detailed report.portable RCD
Additional tests are performed on portable RCD’s including thorough visual inspection for damage. An electrical test is then done for earth continuity, polarity and insulation resistance. The more outlets, the more tests.
Safety switches are not a replacement for a holistic approach to safety in the workplace. It is actually possible to be electrocuted and the saftey switch not detect it. They are a last line of defence when all else fails. Having all portable electric appliances tested reguarly is still required. The difference between an electric shock and electrocution is that electrocution results in death.