Changes to the IET Code of Practice

April 2014

The Code of Practice for In-Service Inspection and Testing of Electrical Equipment was first published in 1994 by the IEE, Institution of Electrical Engineers. By the time the 4^th edition was published in 2012, the IEE had a name change to the IET, Institution of Engineering and Technology. We often get asked if it's okay to use an earlier version of the Code of Practice for our PAT testing course, so I thought it would be useful to look at the changes that have been made to the guidance on PAT testing throughout the 4 editions.

Earth Continuity test

The 1^st edition includes the standard (0.1 + R)Ω limit, but also has some additional limits: 0.5Ω including the supply cable for BS4533 Luminaires, and (0.5 + R)Ω for BS415 Mains Operated Electronic and Related Apparatus. In the 2^nd edition the earth continuity table was dropped and the advice was a (0.1 + R)Ω limit for all equipment. There is no mention of flexing the the cable during the high current test in the earlier editions. The 3^rd and 4^th editions add the extra requirement that “the resistance measurement should be observed while flexing the cable.” Previously this was only a requirement for the low current tests in 1^st and 2^nd editions. The 3^rd edition also introduces the terminology of ‘hard’ and ‘soft’ tests for the high and low current tests. We have some further information in our article about the earth continuity test.

Insulation Resistance test

The limits for the insulation resistance test are quite different in the 1^st edition than they are in later versions. The 1^st edition gives limits for both class 1 and class 2 equipment in both ‘As New’ and ‘In-service’ condition The limit for ‘In-service’ for class 1 is 0.5MΩ, and the limit for ‘In-service’ for class 2 is 1MΩ and a variety of ‘As New’ limits depending on equipment type. In the 2^nd edition this has been simplified to just 1.0 MΩ for class 1, 2MΩ for class 2, and 0.3MΩ for class 1 heating & cooking greater than 3kW. A new option of a 250V dc Insulation test voltage for sensitive electronic equipment is introduced in the 3^rd edition.

Leakage Current test

The 1^st edition briefly mentions that the insulation resistance test may be substituted by an earth leakage measurement where the insulation test is not appropriate. It also gives an example of mineral insulated elements that may not meet the insulation resistance limits, and an earth leakage test could be used instead. There is no mention of the limits for leakage in this section, but Appendix IV on Routine Manufacturing Testing does give some limits: 3.5mA for Class 1 and 0.25 for Class 2.

In the 2^nd edition a new section on leakage tests has been introduced: 15.6 Protective conductor / touch current measurement. This advises that it is used “as an alternative to the in-service insulation test for use if the insulation resistance test either cannot be carried out or gives suspect test results.” It also includes a table for the leakage limits. The 3^rd & 4^th editions remain pretty much the same, however it now described as an “alternative or complimentary" test. We have some further information in our article about carrying out a leakage test.

Substitute/Alternative Leakage Test

The substitute leakage test was first introduced in the 3^rd edition in section 10.1. The previous versions have no mention of this test.

Labels

The advice on PAT labels was pretty consistent in the 1^st, 2^nd, & 3^rd editions. “The date on which re-testing is due or the last test date and re-test period should be stated”. This seems like a sensible approach; a user can look at the PAT label and be able to determine if a re-test is due. In the 4^th edition there was a complete u-turn on this. The new advice is “The date for re-testing should not be marked on the label”. The 4^th edition was introduced after the Professor Löfstedt Report on health and safety legislation recognised that there was an over compliance in PAT testing. This was partially due to PAT contractors often putting annual re-test dates on all labels.

Frequency of testing

The Suggested Initial Frequency of Inspection and Testing of Equipment table remained unchanged in the 1^st, 2^nd, & 3^rd editions. The general advice on the frequency of testing in the 4^th edition has been expanded to emphasis the need for a risk assessment approach to determine the re-test frequency. The table on suggested initial intervals is still included, albeit with some minor changes to some of the periods. It also has some new rows for fixed equipment.

Microwave oven leakage

The 1^st edition has a section on Microwave ovens (15.10). This states that microwave leakage (radiation) can occur if the oven is damaged or corroded but microwave leakage tests are normally only carried out after repair. The 2^nd edition gives some information on functional checks, but no mention of microwave leakage tests. The 3^rd edition recommends that “Microwave leakage should be checked at appropriate intervals”. The 4^th edition dropped the microwave section completely. The preface gives details that the microwave leakage testing is not within the remit of the CoP as it is not an electrical safety test and for this reason it has been removed. Although this is no longer a PAT requirement, we do have an article on carrying out a microwave leakage test.

RCDs

As far as I can see, there is no mention of RCDs in the 1^st & 2^nd editions. In the 3^rd edition it states that “The RCD should be checked for correct operation by plugging it in, switching it on and then pushing the test button.” It also recommends that the trip time is measured. In the 4^th edition the wording for the trip time test has been changed and is now a requirement: “timing tests should take place during the combined inspection and testing.” Table 15.5 on RCD operating characteristics has also been updated.

Production testing

The 1^st, 2^nd, & 3^rd editions all have a large section in the appendix dedicated to Production Testing. The reason given for its inclusion is that these tests may be required after the repair or refurbishment of equipment. In the 4^th edition this entire section of the appendix has been dropped. The preface in the 4^th edition explains “Production testing, previously included in this Code of Practice, has been removed as it is not relevant to in-service inspection and testing.”

Sections introduced in 2^nd edition

The other notable additions to the 2^nd edition are new sections on the Replacement of Appliance Flexes (15.13), and Plug Fuses (15.14)

Sections introduced in 3^rd edition

From a reader's perspectve, the 3^rd edition is a big improvement on the 2 earlier versions. It now includes useful colour diagrams throughout. The colour illustrations in appendix VIII showing examples and information for the visual inspection are a good addition.

Sections introduced in 4^th edition

The 4^th edition has a new chapter - 16. This includes some useful information that was missing in previous versions on New Equipment (16.1), Second-hand Equipment (16.2), and Hired Equipment (16.3).

Purchasing the Code of Practice

If you are buying a copy of the Code of Practice for the City & Guilds PAT course, make sure you get the latest 4^th edition; there are still some online retailers selling the old 3^rd edition. The current C&G 2377-22 syllabus and exam is based on the 4^th edition. The IET Code of Practice for In-Service Inspection and Testing of Electrical Equipment. 4^th edition (ISBN 978-1-84919-626-0). Second hand copies sometimes come up on Ebay, but just make sure that all the pages are intact, the binding quality on the early print runs of the 4^th edition was terrible, so many have missing pages.

5^th Edition Update!

In November 2020, the 4^th edition was replaced with a new 5^th edition. The City & Guilds PAT testing qualification was also updated to reflect the changes in the new edition. The new City & Guilds qualification is 2377-77 and it is still open book, so you will need the latest 5^th edition of the IET for the exam. We also have a new article on the IET Code of Practice, 5^th edition.