All electrical home equipment utilizing mains voltage have to supply not less than 2 ranges of safety to the consumer. That is to make sure that if one of many safety layers have been to fail, there’s the back-up of the second layer nonetheless in place. This makes electrical gear very secure to make use of. Home equipment may be Class 1 or Class 2.
When PAT testing, it is very important first establish the Class of the equipment as Class 1 home equipment are examined otherwise from Class 2 home equipment.
Relying on how precisely the safety is supplied, electrical equipment are put into 5 Lessons of kit development that are Class 1, 2, 3, 0, 01. Of those crucial are Class 1 & 2. For completeness all of the Lessons are described beneath.
CLASS 1
Right here the safety is supplied by a mix of insulation and use of the mains Earth. It’s best proven by referring to an electric fireplace that has been taken aside.
Within the open plug the three wires connecting to the LIVE, NEUTRAL and EARTH pins. Inside the fireplace, the brown LIVE wire and the blue NEUTRAL wire connect with a plastic connector. The inexperienced/yellow Earth wire connects to the metallic case of the fireplace.
The consumer is protected against electric shock by the plastic insulation of the connector. This holds the LIVE and NEUTRAL wires in place and prevents them from touching the metallic case of this electric fireplace. This plastic insulation of the connector is named fundamental insulation.
If this fundamental insulation have been to fail, say as a consequence of extreme motion of the cable the place it touches the metallic case then the consumer of the fireplace can obtain an electric shock if not for the truth that the EARTH wire is current.
By connecting to the metallic case of the electric fireplace, the EARTH wire retains all this metallic at EARTH potential. What this implies is that it’s not possible to get an electric shock even when the metallic case of the fireplace is linked on to the LIVE voltage. In follow a fuse would blow both within the plug or the principle fuse box to protect the consumer.
In abstract, in Class 1 home equipment the consumer is protected by a mix of fundamental insulation and the supply of an EARTH connection, thus offering two ranges of safety.
When PAT Testing Class 1 home equipment, the Earth Continuity and Insulation Resistance checks are carried out.
CLASS 2
In a Class 2 equipment, the consumer is protected by not less than two layers of insulation. For that reason, Class 2 home equipment are also called Double Insulated. They don’t require an Earth connection.
That is finest proven by wanting inside a Class 2 electric drill which has been opened up. Inside one can see that in addition to the plastic connector offering fundamental insulation, there’s extra insulation supplied by the plastic enclosure of the drill.
The consumer is subsequently protected by two separate layers of insulation. When PAT testing Class 2 home equipment, simply the Insulation Resistance take a look at is carried out.
Class 2 home equipment are all the time indicated by the double box image on the score plate.
CLASS 3
Gear constructed to Class 3 normal are designed to be equipped from a particular safety isolating transformer whose output is named Safety Further-Low Voltage or SELV. This should not exceed 50 V AC and is often is beneath 24V or 12V. All Class 3 home equipment are marked by a particular image. There isn’t any use of an Earth in Class III equipment
{The electrical} safety of Class 3 home equipment are taken care of within the safety isolating transformer design the place the separation between the windings is equal to double insulation. The transformer is marked as being appropriate to be used with Class III home equipment.
CLASS 0 & 01
The sort of gear just isn’t for regular use in business or residential environments. It’s simply offered right here for completeness.
Class 0 home equipment rely solely on fundamental insulation for cover from electric shock. For that reason, they don’t have 2 ranges of safety in-built and aren’t allowed on the market. The brass lamp proven right here is an instance of a two wire, metallic cased equipment with solely fundamental insulation. There isn’t any provision for connection of an earth to the bulb holder.
In Class 01 home equipment, there’s provision for an Earth connection, however it’s wired with both twin core cable or solely has a 2-pin plug, so an Earth can’t be linked. AS in Class 0 gear, one depends solely on fundamental insulation for cover from electric shock. As they solely have 1 degree of safety, Class 01 home equipment aren’t allowed on the market.
If throughout PAT testing one comes throughout a Class 0 or Class 01 equipment these may be failed.
IDENTIFYING CLASS I & CLASS II APPLIANCE
Because the PAT testing carried on Class 1 and Class 2 home equipment differ, it is very important establish one from the opposite. There isn’t any different space of PAT testing that causes extra confusion than this and there are various myths surrounding this. It will likely be informative to checklist a few of these.
If there’s a fuse within the plug, then it should be Class 1.
It’s manufactured from metallic so it should be Class 1
The case is plastic so it should be Class 2
It has a 3 core cable so it should be Class 1
The plug has a metallic Earth pin so it should be Class 1
Not one of the above statements is a fool-proof strategy to establish Class I and Class II home equipment and a few are fairly deceptive.
The simplest rule to use is the one beneath.
If the score plate has a double box then the equipment is Class 2. If it doesn’t then it’s Class 1.
Instance – Kettle
The score plate on this kettle clearly has no “double-box” image, so utilizing our rule, it should be Class 1. The Earth connection from the plug is terminated on the surface metallic casing of the heating ingredient. When PAT testing this kettle the Earth Continuity and Insulation Resistance take a look at needs to be carried out.
Instance – Plug-top power provide
The score plate on this Plug-top transformer clearly reveals the “double box” image, so it is a Class 2 equipment. Be aware that it has a plastic Earth pin, as this isn’t required for Class II. (Not all Class 2 home equipment have a plastic earth pin). Simply the Insulation Resistance take a look at needs to be carried out throughout PAT testing.
Instance – Mains extension
The score plate on this extension is moulded within the plastic. It clearly doesn’t have a “double-box” image, so it should be a Class 1. When PAT testing this extension lead the Earth Continuity and Insulation Resistance take a look at needs to be carried out.
Instance – Table lamp
The score plate on this table lamp clearly reveals the “double-box” so it’s a Class 2 equipment. (Be aware that it is a Class 2 equipment that’s largely in a metallic enclosure). The bulb holder is manufactured from plastic and offers the required double insulation. Simply the Insulation Resistance take a look at needs to be carried out throughout PAT testing 삼성tv렌탈.
Instance – Desk fan
The score plate for this fan not solely doesn’t have a “double-box” image, it additionally says that the equipment should be earthed. So that is clearly a Class 1 equipment. Be aware that it doesn’t have any consumer accessible metallic.
Instance – Steel Lamp
If this metallic lamp had a score plate, then it might be a Class 1 equipment because it has an earth level on the lamp holder. Nevertheless, because the score plate is lacking, this must be failed.
Are Class 1 and Class 2 home equipment simply as secure?
As each have 2 ranges of safety in-built, they’re each secure for basic use.
Nevertheless with Class 1 an equipment, one of many layers of safety is supplied by the earth connection. For this to be efficient, the wiring within the constructing needs to be inspected repeatedly to examine that the Earth within the mains socket is accurately taken to the native earth potential. That is often picked off the Earth sheathing of the mains cable coming into the premises, or by driving a neighborhood stake into the bottom. So Class 1 home equipment depend upon the exterior wiring within the constructing to totally present the two ranges of safety.
Class 2 home equipment nevertheless all the time present 2 ranges of safety no matter the standing of the wiring set up. Each layers of safety are constructed into the design making Class 2 home equipment are so much safer than Class 1 home equipment.