Appliance testing includes, extesion cords, power boards, hand tools, kitchen appliances, white goods, workshop equipment etc. In fact anything that is connected to the electricity supply via a plug of some sort needs to be tested.
The frequency of re-testing depends on the type of environment the appliance is being used in. For instance, computers that sit on desk and the cords are rarely disconnected require less testing than hand tools that are constantly being transported, moved from site to site and repeatedly plugged in and unplugged. The frequency of testing is clearly detailed in the standard known as AS/NZS 3760:2010. There is also a standard that especially relates to the construction industry. AS/NZS 3012;2010 These standards set down a lot of requirements for the correct testing that is required to ensure workplace safety.
A typical inspection starts with a thorough visual inspection. During an inspection, a technician is looking for evidence of damage, tampering, wear and tear and tell tales signs of age or stress of the appliance under test. It is common to find extension cords with loose or damage pins, cords that have been stressed from misuse, cords that have been overheated due to exceeding their current rating, cracked power board enclosures, nicks and abrasions. None of which might be immediately fatal but all of which could deteriorate into something much worse.
Once a visual inspection has been completed (and passed) a list of electrical tests are performed, according to the appliance being tested. Appliances are all different and the correct tests must be carried out in the correct fashion. There are two main types of appliances. Type I appliances are earthed appliances. These can be identified by having a three pin plug. If the plug looks to be aftermarket (fitted as a repair perhaps) then further inspection is required to ensure that the appliance really is Type I. The absence of a Type II symbol (two small squares inside each other) or the words “Double Insulated” is usually enough to satisfy any doubts. Tests are then carried out for a Class I appliance. One of the tests is a check to ensure that exposed metal parts are connect to the earth wire.
The next test for a Class I appliance is an insulation resistance test. To ensure that this is correctly carried out, all switches must be closed to ensure that the testing is carried all the way through the appliance. If these basic tests pass, best practice would be to run a live test on the appliance whilst detecting any leakage to earth. There are strict limits for the acceptable levels of leakage for certain types of appliances and these are detailed in AS/NZS 3760:2010.
Something that often gets misunderstood or overlooked when testing, is computer screens and cords. A typical desktop computer consists of a monitor, a case or tower and cords for each of them. The cords are special cords known as IEC leads. As the leads can be removed from both the monitor and the computer case and swapped to other computers or equipment, they are deemed to all be separate items. Therefore, each item needs to be tested. This means that a typical computer requires four tests not one or two. Our technicians will explain this and other not so obvious details so that you have a full appreciation for the scope of works, with no surprises.