Class of Protection in Electrical Appliances

All electrical appliances using mains voltage have to provide at least 2 amounts of protection on the user. Testing and tagging Perth is to ensure that if one of the protection layers were to fail, there is a back-up from the second layer still in place. This makes electrical equipment very safe and secure to work with. Appliances might be Class 1 or Class 2.
When PAT testing, you will need to first identify the Class of the appliance as Class 1 appliances are tested differently from Class 2 appliances.
Depending how precisely the protection is provided, electrical appliance are put into 5 Classes of equipment construction that are Class 1, 2, 3, 0, 01. Of these the main are Class 1 & 2. For completeness all of the Classes are described below.
CLASS 1
Here the security is provided by a mixture of insulation and use in the mains Earth. It is best shown by referring to an electric fire that’s been taken apart.
In outdoors plug these wires connecting on the LIVE, NEUTRAL and EARTH pins. Inside the fire, the brown LIVE wire and also the blue NEUTRAL wire connect to a plastic connector. The green/yellow Earth wire connects for the metal case in the fire.
The user is protected from electric shock through the plastic insulation in the connector. This supports the LIVE and NEUTRAL wires set up and prevents them from touching the metal case of this electric fire. This plastic insulation from the connector is known as basic insulation.
If this basic insulation were to fail, say because of excessive movement of the cable where it touches the metal case then this user of the fire can receive an electric powered shock or even for your proven fact that the EARTH wire occurs.
By connecting on the metal case from the electric fire, the EARTH wire keeps pretty much everything metal at EARTH potential. What this means is that it is impossible to get a power shock even when the metal case in the fire is connected directly on the LIVE voltage. In practice a fuse would blow in the plug or the main fuse box to safeguard the consumer.
In summary, in Class 1 appliances an individual is protected by way of a mix of basic insulation and also the provision of the EARTH connection, thus providing two levels of protection.
When PAT Testing Class 1 appliances, the Earth Continuity and Insulation Resistance tests are executed.
CLASS 2
In a Class 2 appliance, the person is protected by a minimum of two layers of insulation. For this reason, Class 2 appliances may also be referred to as Double Insulated. They do not require an Earth connection.
This is better shown by looking in the Class 2 electric drill which was opened up. Inside one can possibly note that as well as the plastic connector providing basic insulation, there’s additional insulation provided by the plastic enclosure from the drill.
The user is therefore protected by two separate layers of insulation. When PAT testing Class 2 appliances, exactly the Insulation Resistance test is conducted.
Class 2 appliances are always indicated with the double box symbol on the rating plate.
CLASS 3
Equipment designed to Class 3 standard can be supplied from the special safety isolating transformer whose output is called Safety Extra-Low Voltage or SELV. This mustn’t exceed 50 V AC and it is normally is below 24V or 12V. All Class 3 appliances are marked by a special symbol. There is no use of your Earth in Class III appliance
The electrical safety of Class 3 appliances are covered in the safety isolating transformer design the location where the separation between your windings is the same as double insulation. The transformer is marked as being well suited for use with Class III appliances.
CLASS 0 & 01
This type of it technology is not for normal use within business or residential environments. It is just presented in charge of completeness.
Class 0 appliances depend only on basic insulation for protection from electric shock. For this reason, they do donrrrt you have 2 numbers of protection built-in and so are prohibited on the market. The brass lamp shown here is one particualr two wire, metal cased appliance with only basic insulation. There is no provision for connection of your earth to the bulb holder.
In Class 01 appliances, there’s provision with an Earth connection, but it is wired with either twin core cable or only has a 2-pin plug, so an Earth can’t be connected. AS in Class 0 equipment, an example may be dependent only on basic insulation for protection from electric shock. As they only have 1 level of protection, Class 01 appliances are unacceptable available for sale.
If during PAT testing one results in a Class 0 or Class 01 appliance these could be failed.
IDENTIFYING CLASS I & CLASS II APPLIANCE
As the PAT testing continued Class 1 and Class 2 appliances differ, you will need to identify one in the other. There is no other place of PAT testing that produces more confusion than this high a wide range of myths surrounding this. It will be informative to read some of these.
If there is certainly a fuse within the plug, this must be Class 1.
It is made of metal in order that it has to be Class 1
The case is plastic so that it must be Class 2
It includes a three core cable in order that it must be Class 1
The plug carries a metal Earth pin so it should be Class 1
None of the above statements is a fool-proof method to identify Class I and Class II appliances and several can be misleading.
The easiest rule to use could be the one below.
If the rating plate carries a double box then a appliance is Class 2. If it does not that is Class 1.
Example – Kettle
The rating plate for this kettle clearly does not have any “double-box” symbol, so using our rule, it have to be Class 1. The Earth connection in the plug is terminated around the outside metal casing in the heating unit. When PAT testing this kettle the Earth Continuity and Insulation Resistance test should be accomplished.
Example – Plug-top power supply
The rating plate about this Plug-top transformer clearly shows the “double box” symbol, so this is often a Class 2 appliance. Note that it includes a plastic Earth pin, because this is not necessary for Class II. (Not all Class 2 appliances use a plastic earth pin). Just the Insulation Resistance test needs to be accomplished during PAT testing.
Example – Mains extension
The rating plate for this extension is moulded in the plastic. It clearly will not use a “double-box” symbol, in order that it should be a Class 1. When PAT testing this extension lead the Earth Continuity and Insulation Resistance test must be accomplished.
Example – Table lamp
The rating plate about this table lamp clearly shows the “double-box” therefore it can be a Class 2 appliance. (Note that this can be a Class 2 appliance that is largely in a metal enclosure). The bulb holder is made from plastic and offers the mandatory double insulation. Just the Insulation Resistance test should be carried out during PAT testing.
Example – Desk fan
The rating plate just for this fan not only doesn’t possess a “double-box” symbol, it also says how the appliance has to be earthed. So this is clearly a Class 1 appliance. Note that it does not possess user accessible metal.
Example – Metal Lamp
If this metal lamp had a rating plate, it would have been a Class 1 appliance as it comes with a earth point for the lamp holder. However, because rating plate is missing, this could ought to be failed.
Are Class 1 and Class 2 appliances in the same way safe?
As both have 2 levels of protection internal, they are safe for general use.
However with Class 1 an appliance, one in the layers of safety factors are provided by the earth connection. For this to function, the wiring inside the building should be inspected regularly to check the Earth in the mains socket is correctly taken on the local earth potential. This is usually picked off of the Earth sheathing in the mains cable coming into the premises, or by driving an area stake in the ground. So Class 1 appliances depend about the external wiring inside the building to totally provide you with the 2 amounts of protection.
Class 2 appliances however always provide 2 degrees of protection irrespective with the status with the wiring installation. Both layers of protection are designed into the design making Class 2 appliances greater level of safer than Class 1 appliances.