What is a Residual Current Device, RCD, & RCD test tags?
An RCD (Residual Current Device) is a sensitive safety device that switches off electricity automatically if there is a fault. They are also commonly referred to as a Safety Switch. RCDs are in the switchboard and their function is to protect circuits, by tripping power in the event of earth leakage or equipment failure. It continuously monitors the electric current flowing through the circuits it is used to protect.
Having RCDS will prevent electrocution from being fatal. It is vital to the safety of your workplace that your RCD safety switch testing is conducted on a regular basis as they can fail and do have to be replaced from time to time. Failure to replace RCD's can result in a potentially fatal situation. This highlights the importance of RCD safety switch testing, to prevent electrical faults where electricity leaks from the circuit (leakage current testing).
There are 3 main types of RCD’s
- Fixed RCD’s – These are housed in a fuse box and protect a single circuit, or group of circuits. It protects all the wiring and the sockets on a circuit, and any connected appliances, providing the highest level of protection.
- Socket-Outlet RCD’s - This type of RCD only provides protection to the equipment plugged in to this special outlet and the person using that equipment.
- Portable RCD’s – These are very similar to socket RCD’s but they can also be moved from socket to socket as needed. They only provide protection to the equipment plugged in to that socket and the person using it.
All these RCD’s require regular electrical testing to ensure they do not exceed their maximum allowable earth leakage current and are safe to use.
Does your workplace need RCD test tags? Contact us today for a free quote. Learn more about our Test & Tag services, Fire protection services, or Emergency Exit Light Testing services.
Electrical testing and RCD test tags standards
In Australia, RCD test tags and testing must meet a set standard. This is the AS/NZS 3760:2010 in-service safety inspection and testing of electrical equipment. Once leakage current testing has been conducted, the electrician will place RCD test tags on your equipment to show it has met the electrical testing standards and the due date for the next test. Your device must meet the RCD test tags requirements to ensure that it will respond in a fault situation. If it fails, the test (maximum allowable earth leakage current) it will be removed from service and replaced or repaired.
The Maximum Allowable Earth Leakage Current and leakage current testing
RCDs are designed to quickly disconnect a circuit when it detects that the electric current is not balanced between the supply and return conductors of a circuit. Any difference between the currents in these conductors signifies that there is a leakage current, therefore creating a shock hazard. Hence, the importance of leakage current testing and maximum allowable earth leakage current standards. The central protective measure for electrical safety is good insulation. It ensures that no one touches any live conductors and that a short circuit does not occur. Leakage current testing will tell you all about the quality and safety of the insulation. This test is conducted during actual use of the product and determines if the current leakage is too high from the insulation to the housing. It is both a safety and functional test.
The maximum allowable earth leakage current can vary for each piece of electrical equipment, depending on its use and construction, so leakage current testing should always be done by experienced and trained electricians.
What Types of RCD Safety Switch Testing is Performed?
Load Test
A load test can be performed on most power circuits by a technician with a Restricted Electrical Licence. This test measures the power consumption of the equipment when in use. A load test provides a good indication of the equipment’s operating condition. The technician will utilise an RCD tester by plugging it into a power point, tripping the circuit and recording the result. The technician will have to go back and forward to the switchboard to turn the RCD back on between testing 0 and 180 degrees. It is important that the client understands this test is not only testing the RCD, but also the circuit itself. This is a very thorough test if performed correctly and identifies if the RCD and circuit performs effectively. Furthermore, a load testing regime performed on your site will also include the identification of safe Power Points. This is an essential component of RCD safety switch testing.
Injection Test
This electrical testing is performed by a qualified electrician by opening the switchboard and tripping each individual circuit. While doing this, the electrician notes down the specific figures at which the circuit trips at both 180 and 0 degrees. The result of this test per circuit is both results added together and divided by two. For example, DB1 Cb32 tripped at 18 & 31 would have a result of 25. It is important that these results are accurately logged and kept for historical data as RCD's trending towards failing over 300 can be identified and replaced, before they fail and result in a potentially fatal situation. A benefit of injection testing will be the real testing of lighting and fixed power circuits. Therefore, it is important to have a qualified electrician perform your RCD safety switch testing.
Push Button Test
A push button Test is conducted by pressing the button located on the RCD which in turn trips the RCD. The functionality of this RCD is proven by the RCD successfully tripping with the pushing of this button. It is important all push button tests are accurately reported pertaining the individual Switchboard and Circuit Breaker. A push button test is not a completely reliable assessment that the RCD is functioning correctly, therefore it is important that regular electrical testing is completed by qualified electricians. A push button test should be completed at minimum 3 monthly intervals.
Portable Load Test
This test is commonly conducted on portable appliances that contain an RCD. It is important to isolate this test, so your site is not affected by the trip in the situation that the RCD does not work. The equipment is inspected visually, followed by verification of earthing (grounding) continuity, and the quality of insulation between the current carrying parts, and any exposed metal that may be touched is tested. Most portable items containing RCD's will need electrical testing done at more frequent intervals.
Portable Push Button Test
This test is conducted by plugging the portable appliance into power and testing the functionality of the RCD by pressing the push button. This test is most conducted on power boards that contain RCD's. This quick and simple test is commonly used with portable RCDs and should be performed daily or before each time you use the equipment – whichever is the longer. However, it is not particularly accurate and should never be relied on as a reliable assessment of the equipment working correctly.
Want more information about electrical testing? Contact us today for a free quote. Learn more about our Test & Tag services, Fire protection services, or Emergency Exit Light Testing services.