Portable appliance testing (PAT) is the term used to describe the examination of electrical appliances and equipment to ensure they are safe to use. Most electrical safety defects can be found by visual examination but some types of defect can only be found by testing. However, it is essential to understand that visual examination is an essential part of the process because some types of electrical safety defect can’t be detected by testing alone.
A relatively brief user check (based upon simple training and perhaps assisted by the use of a brief checklist) can be a very useful part of any electrical maintenance regime. However, more formal visual inspection and testing by a competent person may also be required at appropriate intervals, depending upon the type of equipment and the environment in which it is used
In practise, many equipment defects can be found during a formal visual inspection. Many potential hazards arise due to the way in which a piece of equipment is used or abused.
The Equipment Enclosure/Casing:
a) Physical damage such as cracks or chemical corrosion
b) Signs of overheating
c) Signs of ingress of fluids or foreign bodies.
a) Correct fit in the mains outlet – not loose and can be removed without difficulty
b) Cracks or damage
c) Signs of overheating
d) Properly tightened off terminal screws
e) Correct wiring
f) Mains flex is properly secured by the cable grip
g) Correct fuse rating and type.
a) Damage, cuts or fraying. Extension leads should be checked along the entire length
b) Joints or connections which are unsafe
c) Appropriate length
d) Correct rating for the equipment.
Visual inspections are to be carried out by a competent person & results need to be logged.
Most manual PAT testers in the market will have preset values stored in the tester which is set by the manufacturer, these typically tend to be worst case scenario values. Some manual testers will allow further tests to continue once the competent person has overruled the value displayed based on knowledge of that equipment type. Some of the more enhanced automated testers will allow the user to write their own test sequences based on the equipment types they are testing.
There are a number of things that need to be considered when determining the frequency of PAT testing. It basically comes down to the higher the risk the more frequent inspection & testing should be carried out. It is down to the ‘Duty Holder’ to assess the electrical appliances within their control & in conclusion implement a preventative maintenance programme for in-service inspection & testing.
It’s important to remember that the Electricity at Work Regulations covers all electrical ‘systems’ & therefor includes equipment operating at all voltages. These items should be added to the asset register, a risk assessment must be carried out & the appropriate test regime implemented with results logged. In some cases it may just be a ‘visual only’ inspection as the amount of testing which can be carried out on this type of equipment may be minimal.
3 Phase equipment is included in the IET Code of Practice (4th Edition) & therefor should be treated the same as any single phase appliance carrying out visual, earth bond & insulation tests. Connections can be made to the PAT tester using 3 phase adapters, should you wish to carry PE Conductor Current tests or Touch Leakage Tests on 3 phase equipment then you need to ensure your tester has the capability to do so or have the appropriate leakage test adapters.
Class I equipment is constructed such that protection against electric shock does not rely on basic insulation alone. In addition to basic insulation around live internal parts, exposed conductive parts are connected to the protective conductor in the fixed wiring of the electrical installation. Class I equipment relies upon a connection to the protective conductor to prevent exposed conductive parts becoming live in the event of a failure in the basic insulation.
Class II equipment is constructed such that protection against electric shock does not rely on basic insulation alone. In addition to basic insulation around live internal parts, supplementary insulation is provided, there being no provision for connection of exposed conductive parts to the protective conductor. Such equipment is often described as “double insulated” and should carry the symbol .
So essentially Class I equipment has an earth which will be visibly terminated in the plug top & has an earth incorporated in the supply cable. Class II equipment does not rely on an earth connection for safety therefor inside the plug you will only see 2 wires (L+N) & is supplied by a 2 core cable.
When testing long extension leads it is very common for most portable appliance testers to indicate a fail on earth continuity, this may lead to false failures & incorrect records. The earth resistance limit for earth continuity stipulated in the IET Code of Practice 4th Edition allows 0.1+R ohms with R being the resistance of the cable.
There is a table in the Code of Practice that will calculate R using the length & cross sectional area of the cable. Some PAT testers will in fact indicate a fail & not allow further tests to continue.
So, to test long extension leads you will need a PAT tester that will either allow the tests to continue once the result shown has been interpreted as a pass by the competent person or a tester that will allow you to programme test sequences factoring in long leads. Some PAT testers will also incorporate a limit calculator function.
One of the big myths surrounding PAT is that we only have to test items with a plug on.
The Electricity at Work Regulations 1989 covers all electrical ‘Systems’ at work and therefore the law does not differentiate between equipment with a plug and that which is wired directly to the supply.
Many companies still fail to include fixed equipment in their risk assessments and asset registers, leaving themselves wide open if something were to go wrong.
During Portable Appliance Testing we try to minimise any disruption by only disconnecting items as we test them. We can work outside of business hours if this helps.
A portable appliance is any equipment which is powered between 40 and 240 volts and which is connected to the electrical mains through a plug, usually 13 amp, but we are also able to test 110 volt, 240 volt including C Form plugs.
We start with a visual inspection checking for:
- Damaged flexes
- Damaged plugs and equipment (overheating, burn marks, discolouration)
- Correctly wired plugs
- Correctly rated fuse
Then a series of tests (depending on the class of equipment), they may include
- Earth continuity testing
- Insulation resistance
- Polarity test
- Earth leakage test
No. The law simply requires an employer to ensure that their electrical equipment is maintained in order to prevent danger. It does not say how this should be done or how often. Employers should take a risk-based approach, considering the type of equipment and what it is being used for. If it is used regularly and moved a lot e.g. a floor cleaner or a kettle, testing (along with visual checks) can be an important part of an effective maintenance regime giving employers confidence that they are doing what is necessary to help them meet their legal duties. HSE provides guidance on how to maintain equipment including the use of PAT.
It is strongly recommended that equipment suppliers formally inspect and test the equipment before each hire, in order to ensure it is safe to use. The person hiring the equipment should also take appropriate steps to ensure it remains safe to use throughout the hire period. The question ‘What is portable appliance testing?’ above gives guidance on what this will entail.
The person doing testing work needs to competent to do it. In many low-risk environments, a sensible (competent) member of staff can undertake visual inspections if they have enough knowledge and training. However, when undertaking combined inspection and testing, a greater level of knowledge and experience is needed, and the person will need:
- the right equipment to do the tests
- the ability to use this test equipment properly
- the ability to properly understand the test results
New equipment should be supplied in a safe condition and not require a formal portable appliance inspection or test. However, a simple visual check is recommended to verify the item is not damaged.
There is no legal requirement to label equipment that has been inspected or tested, nor is there a requirement to keep records of these activities. However, a record and / or labelling can be a useful management tool for monitoring and reviewing the effectiveness of the maintenance scheme – and to demonstrate that a scheme exists.
The frequency of inspection and testing depends upon the type of equipment and the environment it is used in. For example, a power tool used on a construction site should be examined more frequently than a lamp in a hotel bedroom. For guidance on suggested frequencies of inspection and testing, see: Maintaining portable and transportable electrical equipment.
The Electricity at Work Regulations 1989 require that any electrical equipment that has the potential to cause injury is maintained in a safe condition. However, the Regulations do not specify what needs to be done, by whom or how frequently (ie they don’t make inspection or testing of electrical appliances a legal requirement, nor do they make it a legal requirement to undertake this annually).