Electrical appliances are differentiated by a series of IEC protection classes. In PAT Testing it is essential for the person PAT Testing to know the difference in classes and therefore what checks must be completed before declaring the item electrically safe.

Electrical appliances are grouped into 3 main classifications. This again determines the testing procedures.

Class I / 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. There is no symbol for a Class I product so if a rating plate has no symbol on it then it is usually Class I.

Class II / Double Insulated Appliances
There is no earth in Class 2 appliances and the supply cable has only 2 wires – live and neutral. As class 2 appliances are double insulated wiring there is no need for an earth lead. Examples of Class 2 appliances are electric drills and hairdryers. Class II is indicated by double box.

Class III / Safety Extra Low Voltage
These are appliances that are supplied at a low voltage (usually called Separated Extra Low Voltage) which must be less than 50V, supplied with a transformer supply that is also marked. 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.

Class 0 - Non-earthed metal appliance with two core cable. Sales of these items have been banned since 1975.

Class 01 - As Class 0 but appliance has an earth terminal which is unused since two core cable is used.