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All electrical appliances making use of mains voltage have to supply at least 2 ranges of security to the user. This is to assure that if one particular of the protection layers were being to fall short, there is the back-up of the 2nd layer continue to in area. This can make electrical devices incredibly safe and sound to use. Appliances can be Course 1 or Class two. When PAT tests, it is essential to initially identify the Course of the appliance as Course 1 appliances are examined otherwise from Class 2 appliances.Based on how just the safety is furnished, electrical appliance are set into 5 Classes of machines construction which are Course one, 2, three, , 01. Of these the most essential are Course one & 2. For completeness all the Courses are explained beneath.Course 1Here the safety is provided by a combination of insulation and use of the mains Earth. It is ideal shown by referring to an electric fire that has been taken apart.In the open plug the 3 wires connecting to the Are living, NEUTRAL and EARTH pins. Inside of the fireplace, the brown Reside wire and the blue NEUTRAL wire link to a plastic connector. The green/yellow Earth wire connects to the metal scenario of the fire.The consumer is secured from electrical shock by the plastic insulation of the connector. This retains the Dwell and NEUTRAL wires in area and stops them from touching the metallic circumstance of this electric powered fire. This plastic insulation of the connector is known as standard insulation.If this simple insulation had been to are unsuccessful, say because of to too much movement of the cable wherever it touches the steel scenario then the person of the fireplace can receive an electrical shock if not for the simple fact that the EARTH wire is current.By connecting to the metal scenario of the electric powered fire, the EARTH wire retains all this metal at EARTH possible. What this signifies is that it is difficult to get an electric shock even when the steel case of the hearth is related right to the Dwell voltage. In exercise a fuse would blow either in the plug or the main fuse box to secure the person.In summary, in Course one appliances the person is secured by a combination of basic insulation and the provision of an EARTH connection, so supplying two amounts of protection.When PAT Testing Class one appliances, the Earth Continuity and Insulation Resistance checks are carried out.Class twoIn a Class 2 appliance, the person is shielded by at minimum two levels of insulation. For this explanation, Class two appliances are also identified as Double Insulated. They do not require an Earth link.This is best demonstrated by on the lookout inside a Class 2 electric powered drill which has been opened up. Inside of 1 can see that as nicely as the plastic connector furnishing standard insulation, there is extra insulation presented by the plastic enclosure of the drill.The consumer is consequently guarded by two independent levels of insulation. When PAT screening Course two appliances, just the Insulation Resistance exam is carried out.Course 2 appliances are generally indicated by the double box symbol on the rating plate.Course 3Machines crafted to Course three common are made to be provided from a specific protection isolating transformer whose output is acknowledged as Protection Added-Low Voltage or SELV. This need to not exceed 50 V AC and is ordinarily is below 24V or 12V. All Course 3 appliances are marked by a particular symbol. There is no use of an Earth in Class III applianceThe electrical safety of Class 3 appliances are taken treatment of in the protection isolating transformer layout wherever the separation amongst the windings is equal to double insulation. The transformer is marked as getting acceptable for use with Course III appliances.Class & 01This type of devices is not for regular use in business enterprise or residential environments. It is just presented below for completeness.Course appliances depend only on basic insulation for security from electric shock. For this rationale, they do not have two ranges of security designed in and are not allowed for sale. The brass lamp shown listed here is an example of a two wire, metallic cased equipment with only simple insulation. There is no provision for connection of an earth to the bulb holder.In Class 01 appliances, there is provision for an Earth connection, but it is wired with possibly twin core cable or only has a two-pin plug, so an Earth can't be connected. AS in Class machines, one particular is dependent only on fundamental insulation for protection from electrical shock. As they only have one stage of protection, Class 01 appliances are not authorized for sale.If all through PAT tests just one will come throughout a Course or Course 01 appliance these can be unsuccessful.Figuring out Class I & Course II EquipmentAs the PAT testing carried on Course 1 and Course two appliances vary, it is essential to detect one from the other. There is no other location of PAT testing that causes extra confusion than this and there are lots of myths surrounding this. It will be informative to checklist some of these.If there is a fuse in the plug, then it ought to be Class one.It is built of metal so it need to be Course 1The scenario is plastic so it should be Course 2It has a a few main cable so it have to be Class oneThe plug has a metal Earth pin so it should be Course 1None of the above statements is a fool-evidence way to determine Class I and Course II appliances and some are rather misleading.The easiest rule to implement is the 1 below.If the score plate has a double box then the equipment is Course two. If it does not then it is Class 1.Illustration - KettleThe score plate on this kettle clearly has no "double-box" image, so using our rule, it ought to be Course 1. The Earth connection from the plug is terminated on the outside metal casing of the heating factor. When PAT screening this kettle the Earth Continuity and Insulation Resistance check has to be carried out.Illustration - Plug-best energy sourceThe rating plate on this Plug-leading transformer plainly shows the "double box" image, so this is a Course two equipment. Note that it has a plastic Earth pin, as this is not expected for Course II. (Not all Class two appliances have a plastic earth pin). Just the Insulation Resistance examination has to be carried out all through PAT testing.Example - Mains extensionThe rating plate on this extension is moulded in the plastic. It obviously does not have a "double-box" image, so it should be a Class one. When PAT screening this extension lead the Earth Continuity and Insulation Resistance test has to be carried out.Instance - Table lampThe ranking plate on this table lamp evidently demonstrates the "double-box" so it is a Class 2 appliance. (Take note that this is a Course two appliance that is mostly in a metal enclosure). The bulb holder is created of plastic and provides the essential double insulation. Just the Insulation Resistance check has to be carried out through PAT tests.