PAT Testing and Electrical Safety

City & Guilds 2377 qualification

2012-01-29T03:17:00.000-08:00

Overview

There are no qualifications required prior to undertaking PAT testing. There are many training courses designed to bring delegates up to the required standard of competence for carrying this out.

The City & Guilds 2377 qualification is required by some organisations before staff are allowed to carry out PAT testing. Achieving this qualification shows a sound working knowledge of the IEE Code of Practice. The "IEE Code of Practice for in-service inspection and testing of Electrical Equipment" sets the industry standard on how to carry out PAT testing in the workplace.

This qualification is awarded on successful completion of an on-line multiple choice test. There are many organisations around the UK which offer City and Guilds 2377 training courses. Following the course the delegates can take the test at these approved centres. Delegates are allowed to refer to the IEE Code of Practice during the test.

Study resources for preparing for the test.

1. Book by the IET with sample papers with answers. This book is preiced at £13.75 on Amazon.

2. CD with C&G2377 exam simulator from Electacourse. This is £35.97 including VAT for the CD. The download version is priced at £27.70.

3. Free C&G2377-200 practice test from First Stop Safety. This is being trialled at present and is being offered FREE for the first 10 requests in from candidates.

The C&G2377 consists of C&G 2377-100 and C&G 2377-200

City and Guilds 2377 - 100 - Management of Electrical Equipment Maintenance: This is a recommended qualification for anyone who is responsible for inspection and testing. It covers the interpretation of the relevant legislation, assessing the risks, maintenance of records and working out the rquired period for retesting.

City and Guilds 2377 - 200 - Inspection and Testing of Electrical Equipment: This covers areas such as identifying class and type of appliances, being aware of the typical cuses of damage and working out appropriate test methods.

Shortcomings of the C&G2377

Although passing the City and Guilds 2377 exam shows a good understanding of the IEE Code of Practice, there is no practical element to this qualification. Anyone obtaining this Certificate would still need to consider a hands-on session of testing where a number of appliances with various faults are available. This could be achieved by attending a training course or undergoing an in-house training program with a more experienced member of staff.

The other shortcoming of the C&G2377 is that it unnecessarily complicates the business of maintaining electrical appliances in the workplace. In the main, this is a fairly straightforward task, capable of being carried out by a number of people. The majority of faults can in fact be picked up by a good visual inspection including checking the inside of the plug and the fuse. By making this qualification a test of the contents of the IEE code of practice, it covers the whole subject in unnecessary jargon and prevents wider participation in ensuring electrical safety in the workplace.

Summary

Many national PAT testing organsiations insist on the C&G2377 qualification for anyone carrying out PAT testing. This blog is a review of this qualification with tips on how to prepare for the on-line test.

Class I and Class II appliances

2011-12-04T10:19:00.000-08:00

All electrical appliances using mains voltage have to provide at least 2 levels of protection to the user. This is to ensure that if one of the protection layers were to fail, there is the back-up of the second layer still in place. This makes electrical equipment very safe to use. Appliances can be Class 1 or Class 2. When PAT testing, it is important to first identify the Class of the appliance as Class 1 appliances are tested differently from Class 2 appliances.

CLASS 1

Here the protection is provided by a combination of insulation and use of the mains Earth. It is best shown by referring to an electric fire that has been taken apart.

In the open plug the three wires connecting to the LIVE, NEUTRAL and EARTH pins. Inside the fire, the brown LIVE wire and the blue NEUTRAL wire connect to a plastic connector. The green/yellow Earth wire connects to the metal case of the fire.

The user is protected from electric shock by the plastic insulation of the connector. This holds the LIVE and NEUTRAL wires in place and prevents them from touching the metal case of this electric fire. This plastic insulation of the connector is known as basic insulation.

If this basic insulation were to fail, say due to excessive movement of the cable where it touches the metal case then the user of the fire can receive an electric shock if not for the fact that the EARTH wire is present.

By connecting to the metal case of the electric fire, the EARTH wire keeps all this metal at EARTH potential. What this means is that it is impossible to get an electric shock even when the metal case of the fire is connected directly to the LIVE voltage. In practice a fuse would blow either in the plug or the main fuse box to protect the user.

In summary, in Class 1 appliances the user is protected by a combination of basic insulation and the provision of an EARTH connection, thus providing two levels of protection. When PAT Testing Class 1 appliances, the Earth Continuity and Insulation Resistance tests are carried out.

CLASS 2

In a Class 2 appliance, the user is protected by at least two layers of insulation. For this reason, Class 2 appliances are also known as Double Insulated. They do not require an Earth connection.

This is best shown by looking inside a Class 2 electric drill which has been opened up. Inside one can see that as well as the plastic connector providing basic insulation, there is additional insulation provided by the plastic enclosure of the drill.

The user is therefore protected by two separate layers of insulation. When PAT testing Class 2 appliances, just the Insulation Resistance test is carried out.

Class 2 appliances are always indicated by the double box symbol on the rating plate.

IDENTIFYING CLASS I & CLASS II APPLIANCE

As the PAT testing carried on Class 1 and Class 2 appliances differ, it is important to identify one from the other. There is no other area of PAT testing that causes more confusion than this and there are many myths surrounding this. It will be informative to list some of these.

If there is a fuse in the plug, then it must be Class 1.

It is made of metal so it must be Class 1

The case is plastic so it must be Class 2

It has a three core cable so it must be Class 1

The plug has a metal Earth pin so it must be Class 1

None of the above statements is a fool-proof way to identify Class I and Class II appliances and some are quite misleading.

The easiest rule to apply is the one below.

If the rating plate has a double box then the appliance is Class 2. If it does not then it is Class 1.

Example - Kettle

The rating plate on this kettle clearly has no "double-box" symbol, so using our rule, it must be Class 1. The Earth connection from the plug is terminated on the outside metal casing of the heating element. When PAT testing this kettle the Earth Continuity and Insulation Resistance test has to be carried out.

Example - Plug-top power supply

The rating plate on this Plug-top transformer clearly shows the "double box" symbol, so this is a Class 2 appliance. Note that it has a plastic Earth pin, as this is not required for Class II. (Not all Class 2 appliances have a plastic earth pin). Just the Insulation Resistance test has to be carried out during PAT testing.

Example - Mains extension

The rating plate on this extension is moulded in the plastic. It clearly does not have a "double-box" symbol, so it must be a Class 1. When PAT testing this extension lead the Earth Continuity and Insulation Resistance test has to be carried out.

Example - Table lamp

The rating plate on this table lamp clearly shows the "double-box" so it is a Class 2 appliance. (Note that this is a Class 2 appliance that is largely in a metal enclosure). The bulb holder is made of plastic and provides the required double insulation. Just the Insulation Resistance test has to be carried out during PAT testing.

Example - Desk fan

The rating plate for this fan not only does not have a "double-box" symbol, it also says that the appliance must be earthed. So this is clearly a Class 1 appliance. Note that it does not have any user accessible metal.

Example - Metal Lamp

If this metal lamp had a rating plate, then it would be a Class 1 appliance as it has an earth point on the lamp holder. However, as the rating plate is missing, this would have to be failed.

Are Class 1 and Class 2 appliances just as safe?

As both have 2 levels of protection built in, they are both safe for general use.

However with Class 1 an appliance, one of the layers of safety is provided by the earth connection. For this to be effective, the wiring in the building has to be inspected regularly to check that the Earth in the mains socket is correctly taken to the local earth potential. This is usually picked off the Earth sheathing of the mains cable coming into the premises, or by driving a local stake into the ground. So Class 1 appliances depend on the external wiring in the building to fully provide the 2 levels of protection.

Class 2 appliances however always provide 2 levels of protection irrespective of the status of the wiring installation. Both layers of protection are built into the design making Class 2 appliances are a lot safer than Class 1 appliances.

Checking fuses in Plugs

2011-11-13T03:06:00.000-08:00

This subject seems to always causes much confusion during our PAT Training courses - so thought about covering this in our first post.

During the course our advise is:

In a working appliance, if you find a 3 Amp or 5 Amp fuse then there is no need to change this. Just leave this in place.

If you find a 13A fuse, then check the power rating. This is usually found marked in Watts on the rating plate.

If the power rating in leass than 700 Watts then change the fuse to a 3 Amp one. If the power rating is more than 700 Watts then leave the 13A fuse in place.

Considering that these instructions are based at beginners to PAT testing, it should in theory not cause any confusion. However when we pose the following question, nearly everyone gets the wrong answer.

"You find a 5 Amp fuse in a plug and the appliance has a power rating of 900 Watts. Would you leave the fuse in place or change it to a 13 Amp one".

Most delegates say that the fuse should be changed to a 13 Amp one as the power rating is more than 700 Watts, completely ignoring our advise to leave a 3 Amp or 5 Amp fuse in place.

I am really puzzled by this response. Is it because people assume that a 13 Amp fuse provides a better protection than a 3 Amp or a 5 Amp fuse?

I will be grateful for any suggestions on this topic.