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What are the Different Types of PAT Testers?
PAT testing equipment has various levels of functionality. Basic PASS/FAIL kits are very easy to use and relatively inexpensive. They are the preferred choice for a range of businesses, clearly indicating whether an item of electrical equipment has passed or failed. Mains-powered testers require connection to an electrical supply. However, the self-contained battery versions are ideal for large workplaces due to their portability and ease of use. They commonly feature basic light systems that indicate whether electrical items have passed or failed the test.
Basic PAT testing equipment also allows for the establishment of:
- Earth continuity
- Insulation resistance
- Polarity
Basic PAT testers don't display the complete set of electrical test results, and neither do they allow for test configuration or data storage. However, they are often the best choice for obtaining electrical test results quickly and easily.
Advanced PAT testing kits offer the following types of functionality:
- Portable RCD lead testing
- Adjustable PASS test limits
- Substitute and mains powered leakage testing
- Fuse testing
- Lead polarity testing
While a 500V insulation test voltage is typical and suitable for a number of appliances, many PAT testers now include the option of a 250V insulation resistance test. This is essential for testing sensitive and surge-protected equipment, such as IT hardware.
Advanced PAT testing kits are suitable for users with a high level of technical knowledge and expertise. These advanced systems are particularly well suited to facilities management, as they allow for the recording of the location and test status of equipment and appliances. Some of these systems can also transfer the test results to computers for digital interpretation. Test records can be maintained with PAT software.
The PAT Appliance Classes – Defined
Class 1
These electrical appliances only have simple insulation and instead, rely on earth for protection. Such devices are the most common.
Class 2
These electronic devices are outfitted with supplementary insulation and therefore have no reliance on earth for protection. Such devices will be identifiable with a double insulated marking (a square within a square): usually found on the manufacturer’s plate.
Class 3
Low voltage electricals: they are the safest of the classes. They do not require a PAT test, however, the charging lead and cables may do. Class 3 devices will often carry a symbol that contains three vertical stripes within a diamond.
What is a PAT Test?
Defined as Portable Appliance Testing (PAT), it is a routine inspection or examination of various types of electrical equipment and appliances to determine if they are safe to use: this is to prevent accidents or harm to humans, animals and property in the workplace.
Though many defects of electrical equipment can be visually determined, PAT testing also involves a cable inspection using specialist PAT testing tools. The full PAT test is simple to break down:
- Visual inspection of the electrical appliance
- Cable inspection – using PAT testing equipment
The cable inspection portion of a PAT test will include checks and confirmations of the earthing continuity, lead polarity and the integrity of the insulation resistance.
The definition of PAT can be somewhat misleading, however, particularly the word “portable”: appliances that fall under PAT can be any appliance that has a plug attached to connect it to a wall outlet.
There are three distinct classes of electrical appliances: Class 1, Class 2 and Class 3. Class 1 devices are the most dangerous and require a full PAT test.
Why is it important?
It is essential because it keeps the power safe for those in proximity to electrical equipment.
Pat testing prevents accidents by ensuring that there are no potential hazards such as:
Faulty wiring, loose connections or improper grounding of a device. Pat testing ensures proper and complete insulation from the high voltage or low-voltage alternating currents used in electricity distribution systems to establish an adequate ground connection between system parts (elements) that may be exposed to different voltages. It also helps prevent fires caused by defective plug connectors, faulty plugs and poor design flaws on circuit breakers and fuses. This process can help eliminate defects before they cause any harm or injury to people working near these devices.
How Does PAT Testing Work?
The earth continuity test allows for verification of the connectivity between any exposed metal parts and the protective earth pin in the mains plug of a class 1 appliance. This involves connecting the item of electrical equipment to the PAT tester, and the test probe to exposed metal parts. A current is then transferred from the PAT tester along a mains cord to the enclosure. This current then flows back to the PAT tester via the protective earth conductor. This will result in the display of the protective earth path resistance.
The measurement of a predictive conductor current will require the connection of the appliance to the PAT tester. The powering of the appliance will result in a current flowing along the mains supply via live and neutral conductors. The live and neutral currents will ideally be neutral. However, the PAT may highlight an imbalance between the live and neutral currents in some instances.
