The term PAT Testing is commonly used to refer to the process of checking the performance and safety of electrical appliances and systems in the workplace. The term itself acts as an (tautological) abbreviation of the term Portable Appliance Testing although the process is more generally termed In-service Inspection & Testing of Electrical Equipment.

Before looking at how PAT testing is actually performed it is worth considering the purpose behind it and the requirements that drive it. The key purpose is to ensure the safety of electrical equipment but to this end it is also important that records are kept of the safety of individual electrical items and, following an assessment, when they are going to require follow up inspections.

There are many regulations that require the implementation of PAT testing, but the main piece of legislation is the Electricity at Work Regulations 1989 which demands that employers ensure electrical equipment is maintained sufficiently to prevent danger. More specific guidelines on assessing when and how often an appliance requires testing are provided by both the Health & Safety Executive and the Institution of Engineering and Technology.

Initial Checks

The first steps in ensuring the safety of an electrical appliance should ideally be performed by the users of that appliance who should be prompted to carry out basic visual checks whenever they use it. Faults like frayed or loose wires can be identified (and remedied) at any stage by anyone, without specific training and should not therefore remain a danger until the next scheduled PAT test.

Before carrying out a specific PAT test a trained tester should also, using their expertise, first perform a visual check of the appliance to look for external evidence which will be present for the vast majority of faults. Once a formal visual check is complete a PAT test should be performed, again by a trained individual, using the appropriate testing tools (see below).

Who performs PAT Testing

The actual PAT testing can be carried out by anyone with sufficient training and/or who is deemed competent. This may therefore constitute a member of staff in the workplace who has received training such as a City & Guilds qualification (although there is no one recognised qualification that testers require), or an external organisation.

There are obvious benefits to both; using internal staff may bring cheaper labour costs and greater flexibility however using specialist PAT Testing companies would bring benefit from a greater level of expertise - gained through the experience of performing tests day-in day-out - as well as negating the need to buy in the required testing equipment separately. As PAT testing is a task which relies, to a significant extent, on the judgement of the tester, the latter option may ultimately be preferable.

Classes of Electrical Items

The level of testing that each electrical appliance will warrant or require will depend on which class it falls under - as defined by the International Electrotechnical Commission (IEC). One of the key elements of PAT testing is knowing how to identify the class of a certain appliance and the testing it then requires.

Class 1 items refer to those with wires which have insulation only one layer thick and they therefore need to be checked as being earthed. Class 2 items however have wire insulation with two layers and as a consequence do not need to be tested for an earth. Class 3 items, which should come with a labelled transformer, are appliances with a low voltage supply that has to be below 50V. They are often referred to as being supplied with Separated Extra Low Voltage.

Class 2 & 3 items should be labelled as such and therefore appliances without a label should be treated as Class 1. There are some other classes to be aware of which use two core cables: Classes 0 (non-earthed) and 01 (earthed) but these were banned in 1975.

PAT Testing Equipment

There are a variety of tools that can be employed to carry out PAT testing depending on the particular requirements of the job at hand and the capabilities of the PAT tester.

The most basic testing devices that are generally used by staff working as in-house testers within an organisation, are Pass/Fail devices, which, as the name suggests simply give the user a pass or fail reading. These devices are used by in-house testers because of their simplicity and the fact that they therefore do not need the user to have advanced skills and training. The devices themselves will fundamentally test for pass/fail against the criteria of earth continuity, insulation resistance and a wiring check. Some, however, also have accompanying functionality, such as the ability to print the results on labels, which can be tagged to the appliance being tested, and the option of being battery powered to allow the user to move around between appliances more freely. Whilst they may be able to perform tagging the testers won’t store the results and they will therefore need to be logged elsewhere.

For those PAT Testers who are more experienced or highly trained, usually at specialist PAT testing companies, there are more advanced PAT devices available which provide more in depth testing metrics and more advanced functionality to handle those results. For example, testing devices can perform checks such as fuse, lead polarity and RCD tests in addition to the basic functionality and then display and record the more complex readings. Latterly, computerised PAT testers have allowed users to actually store, analyse and compare these results on the device itself rather than transfer them to another computer for analysis.

With the availability of training, tools and third party PAT Testing companies there is no excuse not to ensure that the electrical systems in any workplace aren’t as safe as can be.