Choosing a Tester
There is a wide range of PAT testers and accessories available, this can make choosing the correct tester confusing. As you will have noticed, we only sell a small range testers. We have carefully selected only the best models that represent the best value in terms of ease of use, functionality, reliability and price.
PASS/FAIL Testers / PAT Checkers
Pass/Fail testers only display an indictaion of a pass or fail result, they do not display any measured values. To correctly test an appliance you must interpret the readings the instrument is measuring. A tester with just a pass or fail indication does not allow for this. The IET Code of Practice recommends that equipment failing an earth continuity test using a Pass/Fail tester should have the actual resistance value measured with another test instrument. We do not supply or recommend purchasing a Pass/Fail tester.
Manual PAT Testers
Manual type PAT testers require the appliance details and test results to be manually recorded. This type of test instrument usually has separate tests for Class 1, Class 2, and Extension leads. The test sequence and pass limits are usually fixed which may mean that some manual interpretation of the test readings is required. For example, allowances for increased resistance of supply cords, or different leakage limits for earthed appliances. The manual type PAT testers we recommend are the Kewtech KT71, Seaward Primetest 100 and the Megger PAT150.
Downloadable PAT Testers
Downloadable PAT testers have a wider range of tests and features as well as the ability to download the test data and appliance details. This significantly speeds up the testing process and provides traceability to show the tests have been carried out correctly. A greater range of test sequences as well as the ability to carry out individual tests means that less interpretation of the results is required which makes them easier and quicker to use. The downloadable PAT tester that we recommend is the Seaward Apollo 400.
The most suitable tester
The main factors to consider when selecting a tester are the amount of appliances you will be testing and the type of records you want to keep. The most cost effective solution for testing up to about 500 items, would be an entry level tester. For more than 500 items, the time saved by using a downloadable tester usually outweighs the higher initial cost. For regularly testing larger quantities, the speed and versatility of a professional tester is worth considering.
|Earth Resistance - Low Current||✓||✓||✓||✓||✓||✓|
|Earth Resistance - High Current||✘||✓||✘||✘||✘||✘|
|Lead Polarity Test||✓||✓||✓||✓||✓||✓|
|Insulation Resistance - 500V||✓||✓||✓||✓||✓||✓|
|Insulation Resistance - 250V||✘||✓||✓||✓||✓||✓|
|Earth Leakage Test||✘||✓||✓||✓||✓||✓|
|Substitute Earth Leakage Test||✓||✘||✓||✓||✓||✓|
|230v Load Test||✘||✓||✘||✘||✘||✓|
|110V Load Test||✘||✘||✘||✘||✘||✘|
|RCD Trip Time Test||✘||✘||✓||✓||✓||✓|
|Download Test Data||✘||✘||✘||✘||✘||✓|
|Programmable Test Limits||✘||✘||✘||✓||✓||✓|
|Fixed Equipment Test||✘||✘||✘||✓||✓||✘|
|Barcode Reader Compatible||✘||✘||✘||✘||✘||✓|
|Label Printer Compatibility||✘||✘||✘||✘||✘||✓|
|Calibration Certificate Included||✘||✓||✘||✓||✓||✓|
Earth Resistance - There are two types of earth resistance/continuity test - low current and high current. The high current test is designed to simulate a fault current flowing through the earth path. This will detect any weaknesses in the protective conductor circuit as well as measuring the resistance. The low current test measures the resistance of the protective conductor but does not test for weakness. IT and other sensitive electronic equipment should only be tested using a low current earth continuity test. The IET Code of Practice states that either a low or high current test can be used for measuring earth continuity.
Insulation Resistance - Insulation resistance is usually measured using a 500V DC test voltage. The 250V test is used for testing surge protected equipment that would otherwise fail the standard test as the 500V triggers the surge protection device. Some older IT equipment, pre 1996, that is not built to BS EN 60950 standards should also be tested using a 250V test voltage. IT equipment post 1996 complying with BS EN 60950 is built to withstand a 500V test voltage.
Earth Leakage / Touch Current - This test measures the current flowing through the protective conductor, or in the case of class II appliances, the current flowing through the body should someone touch the appliance (touch current). The test instrument supplies a mains voltage and operates the appliance whilst measuring for any leakage current. An alternative to this test is the Substitute Earth Leakage test, this is performed at a reduced voltage and will not power up the appliance. The substitute leakage test is not as accurate as an earth leakage test.
Load Test - This is usually carried out during the earth leakage test. The test instrument supplies a mains voltage to the appliance and the current consumption and/or the power consumption is then measured. Most testers can only test 230V equipment.
110V Operation - Some testers can perform leakage and load tests at 110V as well as the standard 230V. If a test instrument does not have this ability, a substitute leakage test is usually used as an alternative.
RCD Trip Time - The IET Code of Practice recommends that the trip time of appliances fitted with an RCD is measured. Some PAT instruments such, as the Primetest 250, require an additional isolation transformer to be used when testing portable RCDs to prevent the main RCD within the distribution from tripping during the test. Other PAT testers such as the Megger PAT150 can test portable RCDs without tripping the main RCD.
Battery Operation - Has the advantage of not requiring a mains supply to operate. The limitations of the battery supply means that most of these testers can not perform a high current earth test or earth leakage and load test. Some battery powered testers such as the Seaward Apollo and Megger PAT150 can be plugged into a 230v supply in order to carry out a earth leakage and load test.
Test Sequences and Auto Tests - Can significantly speed up the testing. The correct series of tests and limits are automatically selected according to the class and specific type of appliance.
Barcode Reader - Can speed up the entering of appliance numbers and can also be used to select auto tests.
Label Printers - Some test instruments can be connected directly to a printer to print an appliance label using the data on the tester. Generally this is a slower than using standard labels and the cost of the printer, labels and ink cartridges usually makes this prohibitively expensive.
Qwerty Keyboard - This makes inputting appliance information much easier and quicker than other types.