Functional Classification of Low-Voltage Complete Equipment

Low-voltage complete sets of equipment are classified based on function, protection level, and operational use according to IEC 61439 and appliance protection classes.

Classification by Function (IEC 61439)

Low-voltage assemblies are categorized according to their intended function and operational requirements:

• Distribution Boards (DB): Designed to distribute electrical power to various circuits, often including protection devices like circuit breakers and fuses. Subtypes include:
  • DBO (Distribution Boards for Ordinary Persons): Operated by non-qualified personnel, typically in residential or commercial settings .
  • DBN (Distribution Boards for Skilled Persons): Intended for use by trained personnel, often in industrial environments .
• Motor Control Centers (MCC): Assemblies that control and protect motors, integrating starters, contactors, and overload relays.
• Control Panels: Provide centralized control for machinery or processes, including monitoring and automation functions.
• Switchgear Assemblies: Include devices for switching, protection, and isolation of circuits, ensuring safe operation under normal and fault conditions .

Classification by Protection Level (Appliance Classes)

Electrical equipment is also classified by protection against electric shock:

• Class 0: Basic insulation only, no protective earth; use restricted to dry environments .
• Class I: Basic insulation plus protective earth connection; chassis connected to earth via a conductor .
• Class II: Double or reinforced insulation; no earth connection required.
• Class III: Operates at extra-low voltage (SELV), inherently safe from electric shock.

Classification by Safety and Operational Continuity

Low-voltage complete sets can be further classified based on supply reliability and safety level:

• Class III or IV AC supply: Depending on the safety level, assemblies may be connected to UPS systems or alternate supplies to ensure continuity .
• Battery-backed DC supplies: Provide uninterrupted power for critical systems, switching to AC supply when available .

Compliance and Standards

• IEC 61439-1 & 61439-2: Define general rules, technical characteristics, and verification procedures for LV assemblies .
• IEC 60947 series: Covers low-voltage switchgear and controlgear devices used within these assemblies .
• Low Voltage Directive 2014/35/EU: Ensures equipment meets essential safety requirements for electrical installations .

Summary Table

This classification ensures that low-voltage complete sets of equipment are safely designed, appropriately protected, and compliant with international standards, facilitating reliable operation in residential, commercial, and industrial applications.