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
Testing to use the popular acronym) ensures that electrical appliances continue to
be safe to use.
What’s the best way to carry out PAT Testing?
The Health & Safety Executive (HSE) makes an excellent recommend which is in three
stages. User checks, Formal Visual Inspection and Inspection and PAT testing.
Which is the most cost effective way of carrying out PAT Testing?
Organisations can ensure that electrical appliances are maintained in a number of
ways. The different options below have different advantages and disadvantages.
1. They could employ one of the many PAT Testing companies to carry this out on a
2. They could provide an employee with adequate training, so that they could then
carry out the maintenance in-house
3. Or a mixture of the two, where the PAT Testing company carries out the regular
testing and the competent employee handle all the appliances bought in by employees,
visitors, sub-contractors or customers.
How do you tell if an appliance is Class I or Class II?
If the rating plate has a double box symbol, then the appliance is Class II. Otherwise
it’s Class I.
What is the risk of damage to different 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 this, we can work
out how frequently they need inspection and testing. As a guide, against each item
there is a risk factor indicated with 5 indicating a high probability of damage during
use and 1 indicating a low risk of damage.
Stationary equipment (1)
IT equipment (2)
Movable equipment (3)
Portable equipment (4)
Handheld equipment (5)
Does the environment have an effect on the chance of damage?
Electrical appliances in different work environments will have a differing probability
of damage. To help, we have assigned different risk factors, with 5 indicating a
high probability of damage and 1 indicating a low risk of damage.
Equipment used by the public (3)
Construction sites (5)
How often do you carry out PAT testing?
This is dependent on the following three factors. The IEE Code of Practice (and the
FSS PAT Testing Handbook) gives a detailed breakdown.
The equipment construction i.e. Class I or II
Equipment Type i.e. stationary, portable, handheld etc.
Environment i.e. office, school, factory etc.
What is the best way to record the results of the PAT testing?
A form that is essential at this stage is the Equipment Test Record. This is a permanent
written record of the test results and is proof that the tests have been carried
out. At the top of the form are details about the appliance including how often this
is going to be inspected and tested. The various columns allow one to record firstly
the results of the Formal Visual Inspection followed by the PAT testing results.
What is the point of User Checks?
The person that uses the equipment regularly will be in the best position to know
if it is in a safe condition or working properly. Making the user aware of the early
signs of danger is a great safety measure on most companies.
How do you carry out a Formal Visual Inspection?
This is the most important part of maintaining electrical appliances as it can pick
out faults that cannot be picked out by PAT Testing. It is important to carry this
out in a step by step way. There are essentially five steps to Formal Visual Inspection
and they are outlined below.
Check the cable
Check the appliance
Check the outside of the plug
Check the inside of the plug
Check the fuse rating
How do you check that the appliance has got the right fuse?
This is quite easy to do. If the plug has a 3A or a 5A fuse, then leave this in place.
If the appliance has a 13A fuse, then check the power rating.
If the power rating is less than 700W then change the fuse to a 3A one.
If the power rating is more than 700W then leave the 13A fuse in place.
What tests need to be carried out during PAT Testing?
Different tests are carried out depending on the Class of equipment. Appliances are
tested slightly differently from power cords.
Class I - Test Earth Continuity and Insulation Resistance
Class II - Test only Insulation Resistance
Power Cord - Test Earth Continuity, Insulation Resistance and Polarity
What is the purpose of the Earth Continuity test?
This test is carried out on all Class I appliances. The purpose of the test is to
check that there is a good connection between the Earth pin on the plug and the case
of the appliance. A good connection is defined as having a resistance of less than
0.1 ohms (or 100 milliohms).
The Earth Continuity test is sometime referred to as the Earth Bond test or the Earth
Resistance test. In effect they all measure that there is a good connection between
the mains plug and the Earth point.
What is the purpose of the Insulation Resistance test?
This test is carried out on Class I and Class II appliances. The purpose of this
test is to ensure that there is adequate insulation between the Live parts of the
appliances and the user touchable metal parts. Adequate insulation is defined as
greater than 1 M ohm for Class I appliances and 2 M ohm for Class II appliances.
Are there any other tests required for PAT Testing?
Below are some of the other tests that are frequently available on PAT Testers with
some notes regarding their use.
Earth Leakage (also known as the Protective Conductor test or Touch Current test)
- Sometimes used as a replacement for the Insulation Resistance test.
Load/Run test - Used after repair to check that the appliance is not taking excessive
Flash test - This high voltage test is normally carried during the manufacturing
process or after major repairs have been carried out. It is not required as part
of PAT Testing.
Fuse test - PAT Testers with this feature test for the presence of a fuse in a plug.
This is done by passing a small current into the Live pin of the plug and checking
that a circuit is made by looking for the same current in the neutral pin.
What are the different types of PAT testers?
There are many different makes and models of PAT testers available for sale and these
can be classified as follows for ease of comparison.
PASS/FAIL PAT testers - These testers carry out the PAT test and simply display PASS
or FAIL by checking the test results automatically against internally set thresholds.
PAT Testers with display of results - On these types of testers, the test result
is displayed on an LCD display. The user has to interpret these results to work out
whether the appliance has passed or failed a particular test.
PAT Testers with PASS/FAIL and display - This is a combination of the 2 above.
Downloadable PAT Testers - These testers tend to have an LCD display to display the
results, internal memory to retain a number of test results as well as a PC connection.