Class 0 equipment
“Equipment in which protection against electric shock relies on basic insulation only. There is no supplementary or reinforced insulation.”
An example of Class 0 equipment is older style mains powered Christmas tree lights where the lights are interconnected by a bell flex type cable which is insulated but not sheathed. The recommendation is that these type of appliances should no longer be used.
Class 01 equipment
“Equipment has at least basic protection throughout and is provided with an earthing terminal. The equipment has a power supply cord without a protective earthing conductor and is fitted with a plug without an earthing contact.”
This is specialist equipment and is not for common use.
Class 1 equipment
“Equipment in which protection against electric shock does not rely on basic protection only, but which includes means for the connection of exposed-conductive-parts to a protective conductor in the fixed wiring of the installation.”
The metal parts of Class 1 equipment could assume a hazardous voltage if the basic insulation fails, so there is a requirement that the metal parts are earthed via the protective conductor. Class 1 equipment relies for its safety upon a satisfactory means of earthing from the equipment to the circuit protective conductors of the fixed installation.
Examples of Class 1 equipment are kettles, irons, washing machines etc.
Class 2 equipment
“Equipment in which protection against electric shock does not rely on basic insulation only, but in which additional safety precautions such as supplementary insulation are provided, there being no provision for the connection of exposed metalwork of the equipment to a protective conductor, and no reliance upon precautions to be taken in the fixed wiring of the installation.”
Class 2 equipment is also commonly known as “double insulated”. As there is no earth required for Class 2 equipment there is no reliance on the earthing of the fixed installation for their safety.
Examples of Class 2 equipment are hair dryers, garden power tools etc.
Class 3 equipment
“Equipment in which protection against electric shock relies on supply at SELV and in which voltages higher than those of SELV are not generated.” SELV stands for “Separated extra-low voltage” which means that the equipment operates at a voltage no greater than 50v a.c. or 120v d.c. and has no protective earth connection.
Examples of Class 3 equipment are low voltage lighting etc.