All electrical appliances utilizing mains voltage have to supply at the very least two ranges of defense to the user. This is to make sure that if 1 of the security layers were to are unsuccessful, there is the back again-up of the next layer even now in area. This can make electrical products very risk-free to use. Appliances can be Class 1 or Class two.
When PAT tests, it is crucial to 1st discover the Class of the appliance as Course 1 appliances are tested otherwise from Course two appliances.
Depending on how just the protection is furnished, electrical appliance are set into five Courses of products construction which are Course 1, 2, three, , 01. Of these the most significant are Course 1 & two. For completeness all the Courses are described underneath.
Course one
Listed here the security is offered by a blend of insulation and use of the mains Earth. It is greatest demonstrated by referring to an electric powered hearth that has been taken aside.
In the open plug the a few wires connecting to the Dwell, NEUTRAL and EARTH pins. Inside the fireplace, the brown Are living wire and the blue NEUTRAL wire join to a plastic connector. The environmentally friendly/yellow Earth wire connects to the steel situation of the fireplace.
The user is secured from electrical shock by the plastic insulation of the connector. This retains the Are living and NEUTRAL wires in place and prevents them from touching the metal circumstance of this electrical fire. This plastic insulation of the connector is recognised as essential insulation.
If this primary insulation were being to fail, say thanks to too much motion of the cable in which it touches the metallic situation then the consumer of the fire can obtain an electrical shock if not for the point that the EARTH wire is existing.
By connecting to the metallic circumstance of the electric fireplace, the EARTH wire retains all this steel at EARTH prospective. What this signifies is that it is extremely hard to get an electric shock even when the steel scenario of the fire is connected directly to the Dwell voltage. In follow a fuse would blow both in the plug or the primary fuse box to defend the person.
In summary, in Class 1 appliances the user is protected by a mixture of primary insulation and the provision of an EARTH connection, hence delivering two levels of protection.
When PAT Testing Class one appliances, the Earth Continuity and Insulation Resistance checks are carried out.
Course 2
In a Course two equipment, the consumer is shielded by at the very least two levels of insulation. For this reason, Course 2 appliances are also regarded as Double Insulated. They do not need an Earth link.
This is greatest revealed by hunting inside of a Class two electric drill which has been opened up. Within a person can see that as nicely as the plastic connector delivering primary insulation, there is added insulation delivered by the plastic enclosure of the drill.
The user is therefore secured by two separate levels of insulation. When PAT screening Class 2 appliances, just the Insulation Resistance exam is carried out.
Class 2 appliances are normally indicated by the double box image on the score plate.
Class 3
Gear constructed to Class three conventional are developed to be supplied from a exclusive security isolating transformer whose output is regarded as Security Extra-Minimal Voltage or SELV. This must not exceed fifty V AC and is typically is underneath 24V or 12V. All Course 3 appliances are marked by a distinctive image. There is no use of an Earth in Class III appliance
The electrical basic safety of Course three appliances are taken treatment of in the security isolating transformer layout where the separation between the windings is equal to double insulation. The transformer is marked as currently being suitable for use with Course III appliances.
Class & 01
This variety of equipment is not for usual use in organization or residential environments. It is just offered below for completeness.
Course appliances depend only on essential insulation for safety from electric shock. For this rationale, they do not have 2 concentrations of defense created in and are not authorized for sale. The brass lamp revealed here is an illustration of a two wire, metal cased appliance with only fundamental insulation. There is no provision for connection of an earth to the bulb holder.
In Course 01 appliances, there is provision for an Earth relationship, but it is wired with both twin core cable or only has a 2-pin plug, so an Earth can not be related. AS in Course devices, a person is dependent only on standard insulation for safety from electric shock. As they only have one degree of defense, Course 01 appliances are not permitted for sale.
If throughout PAT testing 1 will come throughout a Course or Course 01 equipment these can be failed.
Identifying Class I & Course II Equipment
As the PAT tests carried on Class one and Class two appliances vary, it is vital to discover 1 from the other. There is no other region of PAT screening that will cause extra confusion than this and there are lots of myths encompassing this. It will be useful to checklist some of these.
If there is a fuse in the plug, then it must be Course one.
It is created of metallic so it will have to be Course 1
The situation is plastic so it have to be Class two
It has a three main cable so it must be Course one
The plug has a metal Earth pin so it should be Class one
None of the earlier mentioned statements is a idiot-evidence way to determine Course I and Course II appliances and some are rather misleading.
The least difficult rule to use is the a person underneath.
If the ranking plate has a double box then the appliance is Course two. If it does not then it is Course one.
Instance - Kettle
The score plate on this kettle evidently has no "double-box" image, so working with our rule, it have to be Class one. The Earth connection from the plug is terminated on the outdoors metallic casing of the heating factor. When PAT screening this kettle the Earth Continuity and Insulation Resistance test has to be carried out.
Example - Plug-top rated energy supply
The rating plate on this Plug-prime transformer clearly exhibits the "double box" symbol, so this is a Course two equipment. Villanyszerelő Budapest Take note that it has a plastic Earth pin, as this is not needed for Course II. (Not all Class 2 appliances have a plastic earth pin). Just the Insulation Resistance examination has to be carried out in the course of PAT tests.
Case in point - Mains extension
The ranking plate on this extension is moulded in the plastic. It evidently does not have a "double-box" image, so it ought to be a Class 1. When PAT screening this extension guide the Earth Continuity and Insulation Resistance test has to be carried out.
Example - Desk lamp
The score plate on this desk lamp clearly exhibits the "double-box" so it is a Class 2 equipment. (Observe that this is a Class two equipment that is largely in a metallic enclosure). The bulb holder is made of plastic and presents the expected double insulation. Just the Insulation Resistance examination has to be carried out during PAT tests.
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