All electrical home equipment utilizing mains voltage have to offer a minimum of 2 ranges of safety to the person. That is to make sure that if one of many safety layers had been to fail, there may be the back-up of the second layer nonetheless in place. This makes electrical gear very protected to make use of. Home equipment will be Class 1 or Class 2.
When PAT testing, you will need to first establish the Class of the equipment as Class 1 home equipment are examined in another way from Class 2 home equipment.
Relying on how precisely the safety is supplied, electrical equipment are put into 5 Lessons of kit building that are Class 1, 2, 3, 0, 01. Of those crucial are Class 1 & 2. For completeness all of the Lessons are described under.
CLASS 1
Right here the safety is supplied by a mixture of insulation and use of the mains Earth. It’s best proven by referring to an electrical hearth 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 person is protected against electrical 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 electrical hearth. This plastic insulation of the connector is called primary insulation.
If this primary insulation had been to fail, say as a consequence of extreme motion of the cable the place it touches the metallic case then the person of the fireplace can obtain an electrical shock if not for the truth that the EARTH wire is current.
By connecting to the metallic case of the electrical hearth, the EARTH wire retains all this metallic at EARTH potential. What this implies is that it’s not possible to get an electrical shock even when the metallic case of the fireplace is related on to the LIVE voltage. In apply a fuse would blow both within the plug or the principle fuse box to guard the person.
In abstract, in Class 1 home equipment the person is protected by a mixture of primary 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 assessments are carried out.
CLASS 2
In a Class 2 equipment, the person is protected by a minimum of two layers of insulation. Because of this, Class 2 home equipment are also called Double Insulated. They don’t require an Earth connection.
That is greatest proven by wanting inside a Class 2 electrical drill which has been opened up. Inside one can see that in addition to the plastic connector offering primary insulation, there may be further insulation supplied by the plastic enclosure of the drill.
The person is due to this fact protected by two separate layers of insulation. When PAT testing Class 2 home equipment, simply the Insulation Resistance check is carried out.
Class 2 home equipment are at all times indicated by the double box image on the score plate.
CLASS 3
Gear constructed to Class 3 customary are designed to be provided from a particular security isolating transformer whose output is called Security Additional-Low Voltage or SELV. This should not exceed 50 V AC and is often is under 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} security of Class 3 home equipment are taken care of within the security 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 will not be for regular use in business or residential environments. It’s simply introduced right here for completeness.
Class 0 home equipment rely solely on primary insulation for defense from electrical shock. Because of this, they don’t have 2 ranges of safety inbuilt and should not allowed on the market. The brass lamp proven right here is an instance of a two wire, metallic cased equipment with solely primary insulation. There isn’t any provision for connection of an earth to the bulb holder.
In Class 01 home equipment, there may be 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 related. AS in Class 0 gear, one depends solely on primary insulation for defense from electrical shock. As they solely have 1 degree of safety, Class 01 home equipment should not allowed on the market.
If throughout PAT testing one comes throughout a Class 0 or Class 01 equipment these will be failed.
IDENTIFYING CLASS I & CLASS II APPLIANCE
Because the PAT testing carried on Class 1 and Class 2 home equipment differ, you will need to establish one from the opposite. There isn’t any different space of PAT testing that causes extra confusion than this and there are lots of 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 made 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 best rule to use is the one under.
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 skin metallic casing of the heating aspect. When PAT testing this kettle the Earth Continuity and Insulation Resistance check needs to be carried out.
Instance – Plug-top power supply
The score plate on this Plug-top transformer clearly exhibits the “double box” image, so this can be a Class 2 equipment. Notice 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 check 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 check needs to be carried out 정수기렌탈.
Instance – Table lamp
The score plate on this table lamp clearly exhibits the “double-box” so it’s a Class 2 equipment. (Notice that this can be a Class 2 equipment that’s largely in a metallic enclosure). The bulb holder is made from plastic and offers the required double insulation. Simply the Insulation Resistance check needs to be carried out throughout PAT testing.
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. Notice that it doesn’t have any person accessible metallic.
Instance – Metallic Lamp
If this metallic lamp had a score plate, then it will 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 protected?
As each have 2 ranges of safety inbuilt, they’re each protected for common use.
Nevertheless with Class 1 an equipment, one of many layers of security 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 appropriately taken to the native earth potential. That is normally picked off the Earth sheathing of the mains cable coming into the premises, or by driving an area 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 nonetheless at all times 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 rather a lot safer than Class 1 home equipment.
