Home | Affiliate | About Us | FAQ | Links | Contact Us | Legal/Privacy | Site Map | Jobs | Forum | News | Tutors Wanted
Home Study Courses
GOLA Exam Simulators
Free Newsletter
Free Google Pack
Book Store
 |
Electrical/Electrician Courses
Other Electrical
PC / IT Technician
Plumbing Course
Language Courses
Other Home Study Courses
Portable Appliance (PAT) Testing Explained contd.
The electrical tests for portable appliances PAT
Portable appliance testing will usually involve the following:
(a) Earth bond continuity tests
(b) Insulation resistance testing
(c) Functional checks
(1) Earth Bond Test (Class 1 equipment only):
Readings should show less than 0.1+R Ohms (where R is the resistance of the lead)
Tested at a current of 1.5 times the rating of the fuse and no greater than 25A for a period of between 5 and 20 seconds or with a short-circuit test current within the range 20mA to 200mA.
(2) Insulation Resistance Test:
The applied test voltage should be approximately 500 Vdc
Class 1 heating equipment < 3kW 0.3M Ohms
Class 1 All other equipment 1M Ohms
Class 2 Equipment 2M Ohms
Class 3 Equipment 250k Ohms
(3) Optional Tests:
Flash Test: No flash-over or breakdown shall occur
Operation/Load test: Compare the reading with stated details on nameplate
Earth leakage test:
Class 1 Handheld Appliances 0.75mA
Other Class 1 Appliances 3.5mA
Class 2 Appliances 0.25mA
Keeping Records
It has been seen that it is a defence under Regulation 29 of the Electricity at Work Regulations for a duty holder to ' prove that he took all reasonable steps and exercised all due diligence to avoid the commission of that offence'. It seems clear that the most effective method by which a duty holder would be able to prove this in court would be by producing records to show that he or she had acted within either the letter or the spirit of the law. Records are therefore essential for a proper and organised system of testing.
Record keeping should be seen as essential. Records provide evidence for the defence in the event of a prosecution and, more practically, such records enable the close monitoring of the electrical equipment. Records can highlight potential faults or adverse trends. Records are also essential for forming an accurate assessment of the necessary frequency of testing. For example, if over a number of consecutive test, few or no failures were recorded then he duty holder may consider reducing the frequency of tests, obviously the converse may also apply.
Replacement of appliance flexes
For flexes to be protected by the fuse in a BS1363 plug there is no limit to their length, providing their cross-sectional areas are as below:
3A 0.5mm2
13A 1.25mm2
Other considerations such as voltage drop may limit flex lengths. Smaller csa's than those given are acceptable if flex lengths are restricted. However, for replacement purposes the above simplified guidance is usually appropriate.
The maximum lengths recommended for extension leads do not apply to appliance flexes or cord sets.
Ratings of Fuses
For the convenience of users, appliance manufacturers have standardised on two plug fuse ratings- 3A & 13A and adopted appropriate flex sizes. For appliances up to 700W a 3A fuse is used, for those over 700W a 13A fuse is used.
The fuse within the plug is not fitted to protect the appliance, although in practice often it does. Portable and fixed appliances are generally designed to European standards for use throughout the European Union. The fuse contained within the plug serves to protect against faults in the flex and can allow the use of a reduced csa flexible cable. This is useful for appliances such as soldering irons, electric blankets etc. where the flexibility of a thin flexible cable is desirable.
Choosing Portable Appliance Testing Equipment
When you are sourcing a portable appliance tester, the first thing you may notice is the large range you have to choose from. For simplicity, PAT testing equipment can be categorised in one of three distinct categories.
Simple PASS or FAIL types
The PASS/FAIL or GO/NO GO, type testers give a simple pass or fail test result allowing no interpretation of the test data. These testers generally only carry out insulation and earth continuity tests. Most PASS/FAIL PAT testers do not have a selectable Earth Continuity test current.
The IEE Code of Practice states that the earth continuity of an electrical appliance can be tested either:
a) - With a current between 20-200mA while flexing the lead of the appliance or,
b) - With a current not less than 1.5 times the rating current of the appliance, and no greater than 25 amps.
If the earth circuit on an appliance is susceptible to corrosion such as those found in a fridge, washing machine, kettle or dryer then you should test these appliances with the higher earth current to ensure any potential corroded earth wires are suitably stressed. To test IT equipment the tester must be able to perform an earth bond test at the lower current of between 20 - 200mA
The disadvantage of this type of tester is that the high current types (usually 25A) are unsuitable for testing IT equipment and the low current types (usually 100mA) are unsuitable for testing general electrical appliances. A further disadvantage with all the PASS/FAIL type of testers is the earth bond pass limit is set, allowing no interpretation of the test result. The IEE Code of Practice requires the earth bond resistance to be no greater than 0.1 Ohms + the resistance of the cable. A tester with a set Earth Continuity limit of 0.1 Ohms will wrongly fail equipment with long leads or low csa that may have a higher resistance. Some testers avoid this by setting the limit higher, usually 0.3 Ohms, but these do not comply with the IEE Code of Practice and may still wrongly fail equipment.
PASS/FAIL testers have the advantage of being easy to use but have a limited practical use.
Manual PAT Testers
Manual PAT testers give much more functionality than the simple PASS/FAIL testers but do require a level of understanding to correctly interpret the test data. As well as the standard Insulation and Earth Continuity tests, many also carry out Earth Leakage and Load tests. Look for testers with selectable Earth continuity test currents enabling the testing of IT equipment.
Downloadable PAT Testers
For testing large amounts of equipment a testers that automates the process and has recording capabilities is more suitable. These testers are able to initiate a pre-programmed test sequence via a shortcut menu. Test data, including the overall PASS or FAIL result, is stored for downloading or printing out. These testers often have a bewildering amount of features, some of the important ones to look for are:
Multiple Earth Paths ability: It is important to choose a PAT tester with the ability to make accurate earth bond measurements, even when multiple earth paths exist. Most PAT testers can measure earth leakage over multiple earth paths, but this is not the same as checking the integrity of an appliance's main earth. For example, consider the common office computer, which often has several other devices attached to it via a screened data cable - for example a printer, monitor or scanner.
An earth return path can still exist even if the earth bond wire in the cord of a computer is faulty.
If you buy a PAT tester that does not automatically cater for earth bond measurement under Multiple Earth Path conditions, the only way to ensure you are actually testing the earth bond of the computer is to disconnect it from all other ancillary equipment. The end result is an increase in test time, and a significant reduction in the number of tests you can do in a day.
On-board help: PAT testers can be complicated instruments and there is nothing worse than having to hunt for that ever-elusive manual. A PAT tester with on-board help that walks you through the tests and displays on-screen connection diagrams when you need them is a definite advantage.
Multiple Voltage Insulation Testing: With the advent of the EMC regulations in Europe, an increasing number of appliances have used filters to manage conducted emission problems. These surge filters can cause inconsistent test results with PAT testers that use a 500V insulation test. Buy a PAT tester with the option of a 240/250V insulation test.
110V Testing: If you intend on testing large amounts of 110V equipment look for a tester that is able to carry out a full Leakage and Load test at 110V. Most testers stating 110V testing are only able to perform sub-leakage tests on 110V equipment.
PAT Equipment manufacturers and suppliers include - Alphatek, Avo, Fluke, Kewtech, Martindale, Megger, Metrel, Seaward, Robin, Transmille
Using PAT Testing Labels
All portable appliance equipment that has been tested and inspected must be clearly identifiable. This usually achieved by labelling the equipment with a PAT Testing label.
The label or sticker must contain the following
a) A unique identification code to enable equipment to be identified
b) The status of the electrical equipment following the testing (PASS or FAIL)
c) The date the appliance was tested together with the re-test period or the re-test date
This information provided on the label is designed so the equipment can be easily identifiable even if several similar items exist within the same premises and it also indicates to a non-technical user if the equipment is due for re-testing or should not be used.
Many modern PAT testers and PAT testing equipment can read bar-coded labels which is particularly convenient for the appliance identification code.
PAT labels or stickers can vary in design but should be durable and hard wearing enough to withstand the period of time between PAT testing without deterioration. The PAT label should be positioned in a prominent position where it is clearly visible.
Portable appliances that fail the PAT test must be put beyond use and clearly labelled with a visible sticker indicating that the appliance has failed.
PAT Testing Software
Modern downloading PAT testers and PAT testing equipment require software to download the PAT testing results to a PC. The PAT testing equipment manufactures usually provide PAT software of their own. Independent PAT testing software is also available.
Legal requirements for landlords
Any person who lets residential accommodation (such as houses, flats and bed-sits and even holiday homes, caravans and boats) as a business activity has a legal requirement to ensure the equipment supplied as part of the tenancy is safe.
The Electrical Equipment (Safety) Regulations 1994 requires that all mains supplied electrical equipment, (wether it be new or second-hand), supplied with the accommodation must be safe. Landlords therefore need to regularly maintain and check the electrical equipment they supply to ensure it is safe.
The supply of goods occurs at the time of the tenancy contract. It is, therefore, essential that property is checked prior to the tenancy to ensure that all goods supplied are in a safe condition. A record should be made of the goods supplied as part of the tenancy agreement and of checks made on those goods. The record should indicate who carried out the checks and when they did it.
It would be strongly advisable to have all electrical equipment checked before the start of each let and also to have the equipment checked at regular intervals thereafter. All test reports listing the equipment, the tests carried out and the results should be retained by the landlord.
Copyright © 2005 ElectaCourse.com all rights reserved Web Design by ElectaCourse.com
Home | Affiliate | About Us | FAQ | Links | Contact Us | Legal/Privacy | Site Map | Jobs | Forum