IEC 61439-3 defines the specific requirements for distribution boards intended to be operated by ordinary persons:
— assemblies intended to be operated by ordinary persons (e.g. switching operations and replacing fuse-links), e.g. in domestic household applications,
— assemblies containing outgoing circuits with protective devices intended to be operated by ordinary persons,
— assemblies for applications where the nominal voltage to earth does not exceed 300 V AC,
— assemblies with a rated current (Inc) of the outgoing circuits not exceeding 125 A and a rated current (InA) not exceeding 250 A,
— assemblies intended for use in connection with the generation, transmission, distribution and conversion of electrical energy, and for the control of equipment consuming electrical energy and for associated data processing,
— enclosed, stationary assemblies,
— assemblies for indoor or outdoor use.
DBOs can contain protection devices, control devices, signalling devices alone or a combination of devices e.g. circuit-breakers, load shedding relay, energy management, communication devices, and lighting control.
IEC 61439-3 does not apply to empty enclosures, individual devices, or self-contained components, such as circuit breakers, fuse switches, and electronic equipment that comply with relevant product standards. It describes integrating devices, self-contained components, or both into a DBO or an empty enclosure forming a DBO.
IEC 61439-3 applies to DBOs designed, manufactured, and verified on a one-off basis or fully standardised and manufactured in quantity. It does not apply to the specific types of assemblies covered by other parts of the IEC 61439 series.
IEC 61439-3:2024 text has been approved in Europe as EN IEC 61439-3:2024 without any changes.