What is PAT Testing?

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2C Fix Appliance

Under the Safety, Health and Welfare at Work Regulation’s S.I NO.299 of 2007 it is now a requirement under Irish law that all businesses’ must carry out PAT Testing on all portable appliances to ensure the welfare and safety of both customers and employees. We regularly get asked questions about PAT Testing, what it is and the legal requirement for it. Powerpoint Engineering have put together the following information that I hope will give you a better understanding of what Portable Appliance Testing is.

Portable appliance testing (PAT Testing) refers to the process of testing electrical portable appliances at regular intervals to ensure they are safe for use. This routine safety check is prevalent not only in the UK, but also in Ireland, Australia and New Zealand. While HSA regulations require electrical equipment and appliances at the workplace be maintained in good condition for safe use, original equipment/appliance manufacturers also advise regular inspection and testing to detect and remedy issues that may render electrical appliances faulty or unsafe over time.

PAT guidelines are specified in AS3760:2013, and the process more aptly defined as “In-service Inspection & Testing of Electrical Equipment” by City and Guilds and IET/IEE. PAT inspections are carried out either manually or by using special testing equipment designed for the purpose. Visual inspections have been observed to be more effective in detecting serious defects such as frayed wires that compromise the safety of the appliance/equipment users. Testing the electrical units, however, help ascertain proper power supply to the unit and also ensure they are in good shape for safe daily use.

Workers who actually use the electrical equipment can themselves check the unit for any visible signs of damage or potential danger before operating it (user check). Alternatively, employers can avail the services of trained technicians to visually inspect (formal visual inspection), or inspect and PAT test all the electrical systems in the workplace to clear them for use.

PAT Testing – Common Tests

The type of electric appliance, its electrical class and risks involved in a specific test will determine the tests that could be performed on the unit. Appliances with single insulated wiring fall under IEC Class I, while those with double insulated wiring belong to Class II.

PAT Testing typically includes these tests in the specified sequence:

Earth Resistance – The test measures the resistance provided by the appliance’s earthing rods. Resistance value must be less than .1Ω.

Earth Continuity – Class 1 appliances are usually subjected to this test to reduce the possibility of severe shocks using an Ohm or a PAT meter. There are three different test conditions that can be applied based on the tester’s discretion.

  • Current strength 100mA – 200mA subject to a max of 12V (aka earth continuity or screen test).
  • Current strength 10A subject to a max of 12V (aka routine test).
  • Current strength 1.5x rated appliance current or 25 A (whichever is higher) (aka type/ bond test).

Insulation Resistance – Class 1 and Class II appliances are put through this test to ascertain the effectiveness of insulation that surrounds live electrical components. An Ohm meter or a PAT meter is used to carry out the test.

  • The test is conducted by applying 500V d.c to the neutral and active conductors of the appliance for 5 seconds.
  • A 0 volt reference is located on earthed parts of class 1 equipment or on the external metal parts, in case of class 2 equipment.
  • Appliances with surge protectors or suppressors are likely to fail this test and need to undergo leakage current test, requiring rated voltage values to remain within 5mA and and 1mA for class I and class II equipment, respectively.
  • Repeating the test several times with references on different external parts will help determine the correct level of insulation of class II appliances.

Polarity – This test helps determine if the leads at the end of the plug fit right terminals on the socket. UK connectivity standard BS7671 requires that live cable should connect with the socket’s right side terminal (when facing the socket outlet).

  • The polarity of pins/sockets in flat three-pin plugs and sockets respectively are usually in the following order – earth (yellow/green), neutral (light blue) and active (brown) – in clockwise direction, and can be visually identified by typically coloured wires (when plug pins facing socket).

Switches/Residual Current Devices/ Earth Leakage Circuit Breakers

  • Are tested using the Press button/ Applied Current methods.
  • The Press button method requires an RCD tester. The test is conducted for a selected half and full range of current strengths to first eliminate nuisance tripping and subsequently clear the unit.
  • Applied current method needs special equipment and expertise. It measures operating time of the switch when sudden current equal to tripping current is passed between active and protective leads.

The frequency of inspection and testing varies based on the type of electrical equipment and its usage (how, where, and when). For example, a power drill or saw used at a construction project site needs regular preventive maintenance to ensure safety of the worker.

PAT tests often figure as a part of the scheduled maintenance plan of a business firm. Though they may be an overhead in low-risk environments, they do ensure a safe workplace.

For further information contact us on 057 866 2162 or email us here.

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