PAT Definitions & Classifications
Portable Appliance Testing
can often appear confusing. Below are some basic definitions
that will hopefully help.
Portable
Appliance
Portable
Appliance Classifications
The Portable
Appliance Test
Portable Appliances
A portable appliance is
classed as an electrical appliance which is intended to be
moved in operation or an appliance that can easily be moved
from one place to another while connected to the supply.
At a simpler level, it
is an appliance that is connected to the electrical supply
by a plug and is between 50 volts and 240 volts. It therefore
covers a broad range of appliances including toasters, hairdryers,
drills, TVs, computers through to washing machines, fridges
etc.
The IEE
Code of Practice groups appliances to be tested into equipment
types including portable appliances, hand held appliances,
stationary equipment, IT equipment, extension leads.that each
require a different testing procedures and pass / fail limits.
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Appliance
Classifications
Electrical appliances
are grouped into 3 main classifications. This again determines
the testing procedures.
1. Class 1 / Earthed Appliances
Class 1 appliances are
protected against electric shock by means of a protective
earth conductor being connected between the supply plug and
the conductive (metal parts) of the equipment. This is in
addition to basic insulation.
Typically, Class 1 appliances
have exposed metal parts although not always. The supply cable
carries 3 wires – Live, Neutral & Earth. Example
of Class 1 appliance would be kettles, irons, toasters etc.
2. Class 2 / Double Insulated Appliances
Class 2 appliances are
protected against electric shock by basic insulation and additional
safety precautions such as double insulation or reinforced
insulation.
In the majority of cases
the appliances are cased in a non-conducting material like
plastic or rubber. They are marked by a square within a square
(as shown below)
There is no earth in Class
2 appliances and the supply cable has only 2 wires –
live and neutral. Examples of Class 2 appliances are electric
drills and hairdryers.
3. Class 3 Safety Extra Low Voltage
Class 3 appliances rely
for protection against electric shock on supply from a safety
extra low voltage (SELV) source. SELV voltages will not exceed
50V and often will be required to be under 24V or even 12V.
SELV systems require specialist
design and there will be no earth facility. The Class 3 construction
mark is above.
Class 3 appliances must be supplied from a safety isolating
transformer to BS3535. The transformer will be marked as follows.
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The Portable
Appliance Test
The Portable Appliance
Test is the combination of a visual inspection and electrical
testing to determine whether portable appliances are safe
and in compliance with Health & Safety regulations.
The procedures for Portable
Appliance Testing have been put together by the IET and are
specified in the Code of Practice.
Portable appliance safety
is reliant on everybody playing their part in the process.
This includes the Users, the Managers with responsibility
for the appliances and the PAT Testers / Inspectors.
The Inspection & Testing
process for Portable Appliances has 3 main parts that will
be explained in detail in the following pages.
-
User Checks
-
Formal Visual Inspection
- Combined
inspections and electrical tests
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