EN60335-Household and similar electrical appliances Safety —Part 1: General requirements

basic insulation
insulation applied to live parts to provide basic protection against electric shock

supplementary insulation
independent insulation applied in addition to basic insulation, in order to provide protection
against electric shock in the event of a failure of basic insulation

double insulation
insulation system comprising both basic insulation and supplementary insulation

reinforced insulation
single insulation applied to live parts, that provides a degree of protection against electric
shock equivalent to double insulation under the conditions specified in this standard
NOTE It is not implied that the insulation is one homogeneous piece. The insulation may comprise several layers which cannot be tested singly as supplementary insulation or basic insulation.

functional insulation
insulation between conductive parts of different potential which is necessary only for the
proper functioning of the appliance

protective impedance
impedance connected between live parts and accessible conductive parts of class II
constructions so that the current, in normal use and under likely fault conditions in the
appliance, is limited to a safe value

class 0 appliance
appliance in which protection against electric shock relies upon basic insulation only, there
being no means for the connection of conductive accessible parts, if any, to the protective
conductor in the fixed wiring of the installation, reliance in the event of a failure of the basic insulation being placed upon the environment
NOTE Class 0 appliances have either an enclosure of insulating material which may form a part or the whole of the basic insulation, or a metal enclosure which is separated from live parts by an appropriate insulation. If an appliance with an enclosure of insulating material has provision for earthing internal parts, it is considered to be a class I appliance or class 0I appliance.

class 0I appliance
appliance having at least basic insulation throughout and incorporating an earthing terminal
but having a supply cord without earthing conductor and a plug without earthing contact

class I appliance
appliance in which protection against electric shock does not rely on basic insulation only
but which includes an additional safety precaution, in that conductive accessible parts are
connected to the protective earthing conductor in the fixed wiring of the installation in such a
way that conductive accessible parts cannot become live in the event of a failure of the
basic insulation
NOTE This provision includes a protective earthing conductor in the supply cord.

class II appliance
appliance in which protection against electric shock does not rely on basic insulation only
but in which additional safety precautions are provided, such as double insulation or
reinforced insulation, there being no provision for protective earthing or reliance upon
installation conditions
NOTE 1 Such an appliance may be of one of the following types:
– an appliance having a durable and substantially continuous enclosure of insulating material which envelops all metal parts, with the exception of small parts, such as nameplates, screws and rivets, which are isolated from live parts by insulation at least equivalent to reinforced insulation; such an appliance is called an insulation-encased class II appliance;
– an appliance having a substantially continuous metal enclosure, in which double insulation or reinforced insulation is used throughout; such an appliance is called a metal-encased class II appliance;
– an appliance which is a combination of an insulation-encased class II appliance and a metal-encased class II appliance.
NOTE 2 The enclosure of an insulation-encased class II appliance may form a part or the whole of the supplementary insulation or of the reinforced insulation.
NOTE 3 If an appliance with double insulation or reinforced insulation throughout has provision for earthing, it is considered to be a class I appliance or a class 0I appliance.

class II construction
part of an appliance for which protection against electric shock relies upon double insulation
or reinforced insulation

class III appliance
appliance in which protection against electric shock relies on supply at safety extra-low
voltage and in which voltages higher than those of safety extra-low voltage are not generated

class III construction
part of an appliance for which protection against electric shock relies upon safety extra-low
voltage and in which voltages higher than those of safety extra-low voltage are not generated

clearance
shortest distance in air between two conductive parts or between a conductive part and the
accessible surface

creepage distance
shortest distance along the surface of insulation between two conductive parts or between a
conductive part and the accessible surface