All electrical accessories using mains voltage need to supply a minimum of two degrees of security to the consumer. This is to make sure that when one of those security layers were to fail, there's the backup of the next coating still set up. This makes electric equipment quite safe to use.
When PAT testing, it's necessary to first identify the Class of this appliance since Class 1 appliances have been analyzed differently in Class 2 appliances.
Based on how precisely the protection is supplied, electric appliance are placed into 5 Classes of gear construction that are Class 1, 2, 1, 0, 01. Of these the main are Class 1 & 2. For completeness all of the Courses are described below.
Here the security is supplied by a mix of insulation and usage of this mains Earth. It's best shown by speaking to a electric fire that's been taken apart.
From the open plug in the 3 wires linking to the LIVE, NEUTRAL and also EARTH pins. Within the flame, the brownish LIVE cable and the blue NEUTRAL cable link into a plastic connector. The green/yellow Earth cable connects to the metallic case of the flame.
The consumer is shielded from electrical shock from the plastic insulation of this connector. This retains the LIVE and NEUTRAL cables in position and prevents them from touching the metal case of the electrical fire. This plastic insulating material of this connector is called basic insulation.
If this simple insulation should happen to fail, state as a result of excessive motion of the cable where it touches the alloy case then the consumer of this flame can get an electrical shock or even for the fact that the EARTH cable is present.
By linking to the metallic case of the electrical fire, the EARTH cable keeps all this alloy in EARTH possible. What this signifies is that it's not possible to find an electrical shock even if the metallic case of the flame is attached straight to the LIVE voltage. In training a fuse will dismiss either in the plug or the primary fuse box to safeguard the user.
To sum up, in Class 1 appliances that the user is guarded by a blend of basic insulation along with the supply of an EARTH link, hence providing two levels of security.
In a Class two appliance, the consumer is shielded by at least two layers of insulating material. Because of this, Class 2 appliances can also be referred to as Double Insulated.
This can be best shown by appearing within a Class 2 electrical drill that has been opened up. Inside one can see that and the plastic connector supplying basic insulation, there's additional insulation offered by the plastic enclosure of this drill.
The consumer is therefore protected by 2 individual layers of insulating material. When PAT testing Course 2 appliances, only the Insulation Resistance evaluation is performed.
Class 2 appliances are constantly indicated by the dual box emblem on the rating plate.
Equipment constructed to Class 3 standard are all made to be provided from a distinctive security isolating transformer whose output is popularly called Safety Extra-Low Voltage or SELV. All Class 3 appliances have been indicated with a particular symbol. There's no usage of an Earth at Class III appliance
The electrical safety of Class 3 appliances have been cared for at the safety isolating transformer design in which the gap between the windings is equal to double insulation. The transformer is indicated as being appropriate to be used with Class III appliances.
This sort of gear isn't appropriate for normal use in residential or business environments.
Class 0 appliances rely just on fundamental insulation for protection against electrical shock. Because of this, they don't have 2 degrees of security built in and aren't permitted for sale. The brass lamp displayed this is a good illustration of a two wire, metal laminated appliance with just standard insulation. There's absolutely not any provision for connection with a ground to the bulb holder.
In Class 01 appliances, there's provision for an Earth link, but it's wired with either twin core cable or just has a 2-pin plugin, so an Earth maynot be connected. AS in Class 0 equipment, one depends solely on fundamental insulation for protection against electrical shock from electrical accessories. Since they only have 1 degree of security, Class 01 appliances aren't permitted for sale.