PAT Testing
Our PAT Testing Procedure
 All testing is carried out under the IEE's (Institute
of Electrical Engineers) Code of Practice for In-Service
Inspection and Testing of Electrical Equipment and conforms to HSE (Health
& Safety Executive) guidelines.
Before any testing commences on an appliance, we will assess the close environment
to make sure testing can be carried out safely and with no risk to either themselves
or people working in the environment.
Inspection and Testing is carried out in
several stages and here is a breakdown detailing the various tests which may
be carried out on electrical appliances during inspection & testing:
Visual
Portable Appliance Inspection
Visual inspections should be carried out by a competent member of
staff who knows what to look at, what to look for and how to avoid danger to
themselves and others. This type of inspection does not require the use of any
specialist test equipment as it is purely a visual inspection. The inspection
should include, when disconnected from the mains supply, the removal of the plug
cover and checking that:
- damage, such as cuts or abrasions to the cable
covering;
- damage to the plug such as the casing is cracked or the pins
are bent;
- non-proprietary joints, including taped, in the cable;
- equipment
that has been used in conditions where it is not suitable, such as a wet or dusty
workplace;
- damage to the outer cover of the equipment or obvious loose
parts or screws;
- overheating (burn marks)
- The cord grip is holding
the outer part of the cable tightly
- The wires, including the earth wire
where fitted, are attached to the correct terminals
- No bare wire is visible
other than at the terminals
- The terminal screws are tight
- There
is no sign of internal damage, overheating, dust or dirt
- Cables located
so as to avoid damage (i.e. run unprotected under carpets)
- Means of disconnection/isolation
readily accessible
- Adequate equipment ventilation
- Cups, plants
and work material correctly placed to avoid spillage
- Equipment positioned
to avoid strain on cord
- Equipment is being operated with the covers
in place and any doors are closed
- Indiscriminate use of multi-way adaptors
and trailing sockets is avoided
- Correct size fuse fitted, BS marked,
ASTA marked
This visual inspection will not include taking the equipment itself
apart.
Combined Portable Appliance Inspections and Tests
The checks carried out as above will have
identified most (but not all) potentially dangerous faults - some deterioration
of the cable, its terminals and the equipment itself can be expected after significant
use. Equipment may also be misused or abused to the extent that it may give rise
to danger. Testing, together with a thorough visual inspection can detect faults
such as loss of earth integrity like a broken earth wire within a flexible cable,
or deterioration of insulation integrity or contamination of internal or external
surfaces.
Examples of some of the tests that we will carry out, as deemed necessary,
are as follows:
Earth Bond Testing
- The safety of certain appliances
depends upon a connection with the earth for its safety.
- A test is
carried out using electrical test equipment to ensure a safe earth is present
in the appliance.
- The test is to ensure that the connection between
the earth pin in the mains plug of the appliance and the metal casing of the
appliance is satisfactory and of sufficiently low resistance.
- (Class
1 equipment only): Readings should show less than 0.1Ω (Ohms) –R1
(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.
Insulation
Testing
- A test is carried out using electrical test equipment to ensure
the insulation resistance in the appliance is at a safe level.
- This
test is used to verify that adequate insulation exists between the mains supply
pins and the earth.
- 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.
Substitute Leakage
Test
- The sub Leakage Test applies a nominal voltage of 40V AC RMS to the
appliance and is applied between the earth pin and both the live and neutral
pins of the supply plug.
- This test can prove useful in situations
where neither conventional insulation nor flash tests are acceptable methods
of testing the insulation of the appliance.
Flash Testing
- This test
is rarely carried out and only then on certain appliances such as power tools.
- A test is carried out to measure the insulation of an appliance if a very
high test voltage is applied to it.
- This test is used to determine that
the insulation is of sufficient strength to prevent breakdown, particularly where
high transient voltages are likely.
Earth Leakage Measurement
- A test
is carried out to monitor the current flow through the earth lead of the appliance.
- The leakage test shows the current being lost through leakage as the difference
in the currents flowing in the live and neutral conductors. This difference is
the total leakage away from the appliance.
- This test is of particular
value when an appliance incorporates a number of sequences, which may change
the electrical characteristics of the appliance during its operation.
Load Test
- A test
is carried out applying a voltage through a current limiting resistor to the
mains supply plug and checks that the current flow will not be excessive when
full voltage is applied to the appliance. The current flow is also compared with
the declared current rating stated on the appliance’s information plate.
Touch Leakage Test
Functional Check
- A test is carried out to ensure that the appliance
is working correctly and basically does what it is supposed to do in the right
environment.
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