Portable appliance testing

A Portable Appliance Test or PAT, in the United Kingdom is a process by which electrical appliances are routinely checked to see whether they are safe. The correct term for the whole process is In-service Inspection & Testing of Electrical Equipment.

When people work with electrical appliances, health and safety regulations say that the appliance must be safe. Many types of equipment require testing at regular intervals to ensure continual safety; the interval between tests depending on both the type of appliance and the environment it is used in.

In the UK, the resulting evidence of Portable Appliance Testing (commonly known as PAT or PAT Testing) is clearly visible to workers in the form of 'Passed' , 'Tested For Electrical Safety' and 'DO NOT USE after' labels affixed to various parts of the electrical equipment they use.

Name

Portable Appliance Testing is abbreviated to PAT. The phrase PAT Testing is in fact a tautology, in the same way that some people say "LCD Display" (see also RAS syndrome). However, the phrase is commonly used in the industry, even though most people realise it is incorrect. The correct term for the whole process is In-service Inspection & Testing of Electrical Equipment.

Legal

Regulations on who must have their equipment PAT Tested

The Electricity at Work Regulations (1989) requires "All electrical systems shall be maintained so as to prevent, so far as is reasonably practicable, any danger". This is interpreted as covering the fixed electrical installation as well as portable and transportable equipment connected to it. The Regulations also state "It is the duty of every employer and self employed person to comply with the provision of these Regulations."

British law (the Electricity at Work Regulations 1989 in particular) requires that all electrical systems (including electrical appliances) are maintained (so far as is reasonably practicable) to prevent danger. Guidance from the Institution of Engineering and Technology (IET, published under the IEE brand) and the Health and Safety Executive (HSE) suggest initial intervals for combined inspection and testing that range from three months (for construction equipment) to five years for inspection and, in many cases, never for testing (certain types of appliance in schools, hotels, offices and shops).

Electrical systems refer to the installation as well as all the appliances connected to it. A qualified electrician would normally inspect the installation at periodic intervals. For an office, this is typically every 5 years and for say a hotel where the risk may be higher, it may need to be done annually. The maintenance of the appliances can largely be carried out in-house in many organisations. This can result in cost savings and more flexibility in when PAT testing is carried out.

The European Low Voltage Directive governs the manufacture or importation of electrical appliances. Compliance to this has to be declared and indicated by the display of the CE mark on the product. The responsibility for this lies with the manufacturer or the importer and is policed by the Trading Standards. However, it is important to have a maintenance regime for electrical appliances. The Electricity at Work Regulations (1989) requires that electrical appliances be maintained so that they remain safe during use. The implementation of this is up to employers. The HSE or the local authority is responsible for the policing of this.

Who can PAT Test

It is not a legal requirement to have attended a course or gained a qualification in order to PAT Test. If you are a competent person and have a basic knowledge of electricity then you can be perfectly capable of testing appliances for electrical safety. It is, however, recommended that an individual wanting to PAT Test attends a course related to the subject matter. There can be much confusion on what needs PAT Testing, what class an appliance is (and therefore which areas to test), and how often appliances legally need to be tested. Proof of a company’s competence in PAT Testing is usually found in the form of a course certificate or qualification.

Carrying out PAT Testing

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This can be done by hiring an external company to test all the electrical products in a business or it can be done in-house by someone who has had some PAT training, either by an official qualification or by attending a health and safety course offered by some electrical health and safety companies.

The following steps are taken when testing a businesses electrical equipment.

User checks

Advising the user of potential danger signs can result in problems being picked up before they can result in any danger. For example, if the power cable is frayed or the plug is cracked, users need to be advised NOT TO USE the appliance and report the fault to a supervisor. This information can be put across, say by the use of a poster or in a memo.

Formal visual inspections

This is a process of simply inspecting the appliance, the cable and the plug for any obvious signs of damage. According to the HSE, this process can find more than 90% of faults. This is the most important part of maintaining appliances.

Combined inspections and PAT testing

At periodic intervals, it is essential to test the portable appliances to measure that the degree of protection to ensure that it is adequate. At these intervals, a formal visual inspection is carried out and then followed by PAT testing. Note the inside of the plug MUST be checked unless it is moulded or there is an unbroken seal covering the screws (bad internal wiring or an unsuitable fuse would cause the item to be classed as dangerous).

The tests that an individual must carry out to declare an item electrically safe is dependant on the class of construction (shown below). Some of these tests are:

• Earth Continuity

• Insulation Resistance

• Polarity of Wiring

Class of Construction

Electrical appliances are differentiated by a series of IEC protection classes. In PAT Testing it is essential for the person PAT Testing to know the difference in classes and therefore what checks must be completed before declaring the item electrically safe.

Class I - Single insulated wiring, which requires an earth connection. There is no symbol for a Class I product so if a rating plate has no symbol on it then it is usually Class I.

Class II - Double insulated wiring, therefore no need for a earth lead. Class II is indicated by double box.

Class III - These are appliances that are supplied at a low voltage (usually called Safety Extra Low Voltage) which must be less than 50V. These appliances are supplied with a transformer supply that is also marked.

Other

Class 0 - Non-earthed metal appliance with two core cable. Sales of these items have been banned since 1975.

Class 01 - As Class 0 but appliance has an earth terminal which is unused since two core cable is used.

See appliance_classes for more info on class of construction.

PAT Training and Qualifications

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It is not stated in the health and safety regulations for an individual to have any qualifications to PAT Test but it does state that it must be done by a competent person who has been given instruction - i.e. Someone who understands the process and can perform the necessary checks in a safe manner.

It is therefore generally recommended that if a company wishes to PAT Test in-house then they have the person who will be doing the testing attend a portable appliance testing training course or at least complete a distance learning course so as to fully understand what it is they are checking for.

The only nationally recognised qualification of competence in PAT is offered by City & Guilds: 'Code of Practice for In-service Inspection and Testing of Electrical Equipment - Vocational 3 (No. 2377)'. although many other non-recognised PAT training courses are available.

Types of PAT Testers

There are many different types of PAT testers available. The main kind for businesses are simple PASS/FAIL PAT testers that are very easy to use, and are aimed at in-house PAT testing. To use the majority of them, one does not require a high level of electrical skill.

There are also advanced PAT Testers, which give much more information and testing features but are mainly aimed at competent persons qualified to City & Guilds 2377. To use the majority of these testers, one does require a higher level of electrical skill.

Pass / Fail PAT Testers

These are the simple-to-use and comparatively much cheaper Portable Appliance Testers for most businesses who will test in-house to carry out the testing. They simply say PASS or FAIL when a test is carried out. You do not need to be an electrician to carry out PAT testing as long as you use a simple PASS/FAIL tester.

Mains Powered Pass / Fail PAT Testers

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The powered Pass / Fail PAT testers are the standard for most businesses who test in-house. It is ideal for those wanting to carry out in-house testing of electrical appliances in offices, hotels, schools, nursing homes, factories and construction sites. You usually get test result labels, which are attached to the electrical equipment that is being tested with a date stamp to show when the item next needs to be tested. The simplicity of these devices make them very popular with small businesses simply because of the PASS or FAIL display when a test is done. These testers are also safe for use on PCs and other IT equipment.

The newer battery powered testers offer much more flexibility as the tester can be moved to the equipment as appose to the other way round.

Battery Powered Pass / Fail PAT Testers

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These are the newer and more convienient pass / fail PAT testers, which you can take to the appliance to be tested making testing multiple items in a busineess much quicker. They usually come with rechargable batteries

The battery powered testers are fast replacing the older powered units. A common one is the BattPAT as shown right.

The newer battery powered PAT testers have a simple "lights" system. They have a "Pass" light , a "Fail" light, options for Class I metal / plastic or Class II. They also will show:

• Earth Continuity
• Insulation Resistance
• Polarity

Advanced PAT Testers (Also known as Electricians PAT Testers)

These PAT Testers give the actual readings from the PAT tester in Ohms (or Mohms) for the person testing to interprete. A knowledge of electrical readings is required hence why these type of PAT Testers are designed for use by an electrician / someone with electrical qualifications. Also some hybrid designs will have the electrical readings along with a PASS / FAIL option.

Advanced PAT Testers

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These are PAT Testers designed to display more information than just pass or fail. As well as giving the Pass / Fail results it will give readings for the tester to interprete. Some of these include:

• Earth Continuity Resistance (aka Earth Bond) tests with a measurement range of 0 - 1.99Ω at high test currents (usually 8A, 10A or 25A) and lower test currents (in the range 20mA to 200mA), enabling a complete range of appliances including personal computers to be tested.
• Insulation Resistance tests at test voltages of 500Vdc or 250Vdc.
• Protective Conductor/Touch Current measurement (sometimes referred to as Earth Leakage tests on some older PAT units).
• Fuse test.
• Lead Polarity
• Some units incorporate an RCD test function.

• Testing both 230V and 110V appliances

Computerised PAT Testers

Also some advanced PAT testers have the capability of downloading the information to a pc or laptop for recordings (an example of such a unit is shown to the right).

Calibration of PAT Testers

As PAT Testers are sophisticated instruments, it is important to make sure that they are continuing to measure correctly. If a company fails to check and maintain calibration, it could face difficulty substantiating any measurements in the event of a claim. It is usually recommended that calibration is carried out annually on a PAT testing unit.

When a PAT Tester is calibrated it is re-configuring it to match the original specification. This includes:

• Calibrating the unit back to National Standards. This is best performed by the product manufacturer (if they offer a calibration service) or a laboratory accredited by UKAS
• If it is mains powered, then a safety test must be carried out.
• A calibration certificate should be issued to prove the PAT unit has been electrically tested.

See also

• Test and tagging

External links

• IET/IEE Code of Practice for In-Service Inspection and Testing of Electrical Equipment
• HSE Maintaining electrical equipment safety
• http://testingappliances.blogspot.com/