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Pat Testing Information
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Information on class, type and environment in which electrical equipment is used and how it impacts the frequency and type of testing applied.
Class of Equipment
The method of construction of an electrical appliance determines it's Class and the tests that we carry out.
All electrical appliances using mains voltage have to provide at least 2 levels of protection to the user. This is to ensure that if one of the protection layers were to fail, there is the back-up of the second layer still in place. This makes electrical equipment very safe to use.
Depending on how exactly the protection is provided, electrical appliances are put into 5 Classes of equipment construction which are Class I, II, III, 0 and 01. Of these the most important are Class I & II.
In Class I appliances the user is protected by a combination of basic insulation and the provision of an EARTH connection, thus providing two levels of protection.
In a Class II appliance, the user is protected by at least two layers of insulation. For this reason, Class II appliances are also known as Double Insulated. They do not require an Earth connection. Class II appliances are always indicated by the double box symbol on the rating plate.
Equipment built to the Class Ill standard is designed to be supplied from a special safety isolating transformer whose output is known as Separated Extra-Low Voltage or SELV. This must not exceed 50 V AC and is normally is below 24V or 12V. There is no use of an Earth in Class III appliance.
The electrical safety of Class III appliances are taken care of in the safety isolating transformer design where the separation between the windings is equivalent to double insulation.
CLASS O & 01
This type of equipment is not for normal use in business or residential environments. It is just presented here for completeness.
Class 0 appliances depend only on basic insulation for protection from electric shock. For this reason, they do not have 2 levels of protection built in and are not allowed for sale.
In Class 01 appliances, there is provision for an Earth connection, but it is wired with either twin core cable or only has a 2-pin plug, so an Earth cannot be connected. As in Class O equipment, one is dependent only on basic insulation for protection from electric shock. As they only have 1 level of protection, Class 01 appliances are not allowed for sale.
Types of Electrical Appliances
Electrical appliances are separated into different Types to allow us to assess how likely they are to be damaged when they are being used. Knowing the type of an electrical appliance, we can work out how frequently it needs inspection and testing. As a guide, against each item there is a risk factor shown with 5 indicating a high probability of damage during use and 1 indicating a low risk of damage.
Stationary equipment (risk factor of 1)
This is equipment that is greater than 18 kg in weight and is not provided with a carrying handle e.g. refrigerator, cooker, washing machine or dishwasher.
Generally, there is very low risk of damage to this type of appliance. They are rarely moved and so there is little risk of the cable or plug getting damaged. However, these types of appliances are still required to be fully tested.
An electric cooker which is run off a fused mains spur also needs to be included in the list of items that are maintained. Some assume that PAT Testing only includes appliances with a plug. In actual fact, it would need to include everything that is capable of being moved. This is because if the appliance can be moved, then there is a possibility of damage to the mains cable.
Information technology (IT) equipment (risk factor of 2)
This includes all types of business equipment e.g. computers, fax machines, printers or photocopiers.
These are also fairly low risk appliances. They are generally enclosed in plastic and rarely moved, thus presenting little risk to the user.
Movable (transportable) equipment (risk factor of 3)
These are equipment that is either
There is slightly more risk with these types of appliances as they can be moved quite frequently. They will need regular inspection and testing.
Portable equipment (risk factor of 4)
These are appliances of less than 18kg in weight that is intended to be moved while in operation or an appliance that can easily be moved from one place to another e.g. toaster, food mixer, kettle or chip fryer. Appliances of this type are easily moved and can be used heavily and this is reflected in their higher risk factor.
An extension lead is necessary when a convenient mains socket is not available. An RCD extension lead is an extension lead that includes an RCD. Multi-way adaptors are used when there are insufficient mains sockets available. RCD adaptors are used to provide protection for people using portable appliances particularly when they are being used outdoors. Generally all of these can be treated as Portable appliances.
Hand-held equipment (risk factor of 5)
A hand-held appliance or equipment is portable equipment intended to be held in the hand during normal use e.g. angle grinder, power drill, sander, hedge-cutter, iron or hair dryer.
Hand-held appliances have the highest probability of damage during use. This is because they are held in the hand during use, so there is a high likelihood of dropping the appliance and damaging the casing or plug. The cable is flexed every time the appliance is used, so the chances of this fraying or twisting is very high. Finally, any damage to the appliance, cord or plug has a higher chance of causing an electric shock to the user.
It seems obvious that electrical appliances in different work environments will have a differing probability of damage. In this chapter we will look at how this can be categorised.
For the different work environments, we have assigned different risk factors, with s indicating a high probability of damage and 1 indicating a low risk of damage.
Offices (risk factor of 1)
Offices are generally considered to be low risk. Appliances such as PCs are rarely moved and in most modern well run offices, the risk of damage even to portable appliances is small. In other organisations such as shops, residential homes and hotels, equipment used by staff in offices is also classed as low risk for the same reasons.
Schools (risk factor of 2)
Equipment in schools for use by the pupils has a higher risk of damage. This is because there is a larger number of people using the equipment and generally there is less care taken over looking after them.
Equipment used by the public (risk factor of 3)
This applies to equipment in shops, pubs, hotels and residential homes provided for use by the customers. Again, this type of equipment could be used by a variety of people, it is important to inspect them for damage on a regular basis. e.g an arcade machine in a pub.
Industrial, including factories, workshops & commercial kitchens (risk factor of 4)
Environments such as a metal or wood workshop tend to be a lot harsher as often people are working to tight timescales, and equipment generally tends to get quite heavy use.
Construction sites (risk factor of 5)
Building sites quite harsh environments and being outdoors tend to also be affected by dust, water and debris from various construction activities. This type of environment presents the highest risk of damage to portable appliances. It is for this reason that 110V appliances are used to reduce the risk of serious injury if an appliance were to develop a fault and cause a shock to a user.
Why Do We have to PAT Test
Electrical appliances start off perfectly safe, but with use can deteriorate to an extent where there is a risk of an electric shock or a fire. Just as regular MOT checks ensure the safety of cars on the road, Portable Appliance Testing (or PAT to use the popular acronym) ensures that electrical appliances continue to be safe to use.
A vacuum cleaner for example would be used heavily in a school or a hotel. In time it is likely that the cable may start pulling out of the plug or the wire could start fraying.
If we don't have a system of maintenance where these types of faults are picked up and put right it is very possible that someone would get an electric shock.
For example there would be risk of a fire where a blown fuse has been replaced with one of the wrong value or even worse, by a piece of tin-foil. As shocking as this may seem, there are many examples where this is done to save time. The intention is to replace the tin-foil with the correct fuse at a later stage but somehow this never gets done.
If the appliance were to develop a fault then the tinfoil will not act as a fuse and there is a risk of a fire breaking out.
Increasingly, Insurance companies are stipulating Portable Appliance Testing as a necessary condition of insurance on most businesses. If there was a fire and the management in a company could not show that regular PAT Testing had been carried out, some insurance companies could take this into account when arriving at settlement figures.
In addition to the above reasons, there are a number of Health & Safety regulations that are in place to protect employees from danger. These imply directly or indirectly that employers have to ensure that electrical appliances do not cause any danger to staff.
The key points from these are summarised below.
The Health & Safety at Work Act 1974
Places a duty of care on employers and employees to ensure the safety of everyone at work, including the self-employed.
The Management of Health & Safety at Work Regulations 1999
These regulations require the employer to assess the risks to the health & safety of employees, visitors, customers and sub-contractors.
The Provision & Use of Work Equipment Regulations 1998
Employers shall ensure that work equipment is so constructed that it is suitable for the use to which it is put.
Electricity at Work Regulations 1989
These regulations are very relevant to the use of electrical appliances at work. They require electrical systems to be maintained so that they remain safe during use. This refers to everything electrical in the workplace, from the wiring in the building to electrical appliances.
PAT Testing is concerned with the maintenance of the electrical appliances.
European Low Voltage Directive
This Directive governs the manufacture or importation of electrical appliances. Compliance to this has to be declared and indicated by the display of the CE mark on the product. The responsibility for this lies with the manufacturer or the importer and is policed by the Trading Standards.
PAT Testing is a way of maintaining electrical appliances and it
• Reduces the risk of fires
• Prevents users getting an electric shock
• Is a legal requirement in the workplace