Exposed-conductive part: conductive part of equipment that can be touched and that is not live under normal conditions, but that can become live when basic insulation fails [this term is defined in the IEC 60050-195-2021].
The British standard BS 7671 defined the term in question in much the same way as IEC 60050-195-2021:
Exposed-conductive-part: conductive part of equipment which can be touched and which is not normally live, but which can become live under fault conditions.
The term “exposed-conductive-part” refers to those conductive parts of electrical equipment which are accessible to the touch and which, unlike live parts, are not under voltage in normal conditions when all means of protection are intact, including the basic insulation. A person in a building has numerous contacts with exposed-conductive-parts during which he or she is not exposed to the risk of electric shock.
In a single fault condition, when the basic insulation of a hazardous live part is damaged, an exposed-conductive-part may become voltage. It will then pose a real danger to a person who touches an exposed-conductive-part and could receive a dangerous electric shock.
Examples of Exposed-Conductive-Parts
As an example, exposed-conductive-parts primarily include metal enclosures and touchable fittings of class 0 and class I equipment, such as the metal housings of refrigerators, washing machines, electric stoves, metal fittings of fixtures, etc.
Exposed-conductive-parts are separated from live parts by means of basic insulation. Therefore, exposed-conductive-parts are parts of class 0 and class I electrical equipment, e.g. their metal sheaths.
The accessible conductive parts of class II electrical equipment, such as their metal sheaths, are separated from the live parts by double insulation, which is the combination of basic and supplementary insulation or the equivalent reinforced insulation. In the event of damage to the basic insulation or partial damage to the reinforced insulation of live parts, the accessible conductive parts of class II electrical equipment are not live and therefore do not present a danger to humans. They are therefore not exposed-conductive-parts.
IEC standard 61140, which classifies low-voltage electrical equipment in terms of protection against electric shock and lays down the fundamental requirements for electrical equipment of classes 0, I, II, III, refers to the conductive parts in question as accessible conductive parts of class II electrical equipment.
The accessible conductive parts of class 3 electrical equipment, which are their metal sheaths, must not be regarded as exposed-conductive-parts either. class III equipment operates at extra-low voltages. Its live parts are not hazardous live parts and cannot cause a dangerous electric shock.
The insulation of the live parts of class III electrical equipment is not basic insulation because the basic insulation is the insulation of the hazardous live parts. Therefore, the metal sheaths of class III electrical equipment cannot be exposed-conductive-parts.
What Is a Conductive Part?
A conductive part is an electrical component that allows current to flow through it. Current is the flow of electrons, and it is what powers electronic devices. Conductive parts are made of materials that allow electrons to flow freely, such as metal.
Conductive parts are essential to the functioning of any electronic device. They help to create circuits, which are pathways for current to flow. Without conductive parts, electronic devices would not be able to operate.
Conductive parts come in a variety of shapes and sizes, and they can be found in almost any type of electronic device. The most common type of conductive part is the wire. Wires are used to connect different components together and create circuits.
Is a Water Pipe an Exposed-Conductive-Part?
Some people believe that water pipes are exposed-conductive-parts, but this is not the case. Water pipes are not considered to be exposed-conductive-parts because they are not intended to carry an electrical current. Additionally, water pipes are not generally made of conductive materials. If a water pipe were to come into contact with an exposed-conductive-part, it would not create an electrical hazard.
Do Exposed-Conductive-Parts Need Bonding?
It’s a common misconception that all exposed-conductive-parts (ECPs) in electrical equipment need to be bonded. The truth is, only certain ECPs require bonding, and the NEC provides clear guidance on which ones need to be bonded and how to properly bond them.
Here’s a quick overview of when bonding is required for ECPs:
1) All ECPs that are part of the electrical circuit and are intended to come into contact with humans or animals must be bonded. This includes any ECPs that could become energized due to a fault in the equipment or system.
2) Any ECP that is not part of the electrical circuit but could become energized due to a fault in the equipment or system must also be bonded.
3) Any ECP that is not part of the electrical circuit but could become energized due to contact with another conductive object must also be bonded.
4) Finally, any ECP that is not part of the electrical circuit but could become energized due to inductive or capacitive coupling must also be bonded.
- IEC 60050-195-2021
- BS 7671
- IEC 61140-2016