Appliance classes

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Appliance classes

In the electrical appliance manufacturing industry, the following IEC protection classes are used to differentiate between the protective-earth connection requirements of devices.

e appliances have no protective-earth connection and feature only a single level of insulation.

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In the electrical appliance manufacturing industry, the following IEC protection classes are used to differentiate between the protective-earth connection requirements of devices.

Class 0

These appliances have no protective-earth connection and feature only a single level of insulation. They were intended for use in dry areas. In most countries, the sale of Class 0 mains

Mains

Mains may mean or refer to, or be a subject of:* Mains electricity * Electricity transmission* Public utility, about "mains services", including electricity, natural gas, water, and sewage disposal...
-voltage appliances is prohibited today, as a single fault could cause an electric shock

Electric shock

An electric shock can occur upon contact of a human's body with any source of voltage high enough to cause sufficient Electric current through the muscles or hair....
or other dangerous occurrence. The International Electrotechnical Commission

International Electrotechnical Commission

The International Electrotechnical Commission is a Non-profit organization, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies ? collectively known as "electrotechnology"....
is in the process of removing provisions for Class 0 devices from its standards. It can be expected that the Class 0 concept will eventually disappear from the international market, in favour of Class II devices.

Class I

These appliances must have their chassis connected to electrical earth

Ground (electricity)

In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
(US: ground) by an earth conductor (coloured

IEC 60446

International standard IEC 60446 defines basic safety principles for identifying electrical conductors by colours or numerals, for example in electricity distribution wiring....
yellow/green in most countries, green in the U.S., Canada and Japan). A fault in the appliance which causes a live conductor to contact the casing will cause a current to flow in the earth conductor. This current should trip either an overcurrent device (fuse

Fuse (electrical)

In electronics and electrical engineering a fuse is a type of overcurrent protection device. Its essential component is a metal wire or strip that melts when too much current flows, which breaks the electrical network in which it is connected, thus protecting the circuit's other components from damage due to excessive current....
or circuit breaker

Circuit breaker

A circuit breaker is an automatically-operated Electricity switch designed to protect an Electrical network from damage caused by Overcurrent or short circuit....
) or a residual current circuit breaker (ground fault circuit interrupter [GFCI]) which will cut off the supply of electricity to the appliance.

Class II

A Class II or double insulated electrical appliance is one which has been designed in such a way that it does not require a safety connection to electrical earth

Ground (electricity)

Voltage

Electrical tension is the potential difference between two points of an electrical or electronic circuit, expressed in volts. It is the measurement of the potential for an electric field to cause an electric current in an electrical conductor....
becoming exposed so that it might cause an electric shock

Electric shock

An electric shock can occur upon contact of a human's body with any source of voltage high enough to cause sufficient Electric current through the muscles or hair....
and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having two layers of insulating

Electrical insulation

An insulator, also called a dielectric, is a material that resists the flow of electric current. An insulating material has atoms with tightly bonded valence electrons....
material surrounding live parts or by using reinforced insulation.

In Europe

Europe

Europe is, conventionally, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural , the Caspian Sea, and by the Caucasus Mountains to the southeast....
, a double insulated appliance must be labelled "Class II", "double insulated" or bear the double insulation symbol (a square inside another square).

See also double switching

Double switching

Double switching is the practice of using a multipole switch to close or open both the positive and negative sides of a Direct current electrical circuit, or both the hot and neutral sides of an Alternating current circuit....
.

Class III

A Class III appliance is designed to be supplied from a SELV (Separated or Safety Extra-Low Voltage) power source. The voltage from a SELV supply is low enough that under normal conditions a person can safely come into contact with it without risk of electrical shock. The extra safety features built into Class I and Class II appliances are therefore not required.