Low-voltage switchgear and controlgear assemblies - Part 3: Distribution boards intended to be operated by ordinary persons (DBO)

Overview

IEC 61439-3:2024 is the product part of the low-voltage assemblies family devoted to distribution boards that ordinary persons may operate (DBO). Such persons can perform switching and replace fuse-links. Typical examples are small final distribution boards. The second edition was published on 26 March 2024, runs to 130 pages and replaces the 2012 edition; a commented version is also available.

The scope limits are clear from the publication abstract: nominal voltage to earth does not exceed 300 V AC (DC limits are under consideration). Outgoing circuits may be rated up to 125 A (Inc) and the assembly up to 250 A (InA). The outgoing circuits are fitted with protective devices such as those under IEC 60898-1, IEC 61008/61009, IEC 62606, IEC 62423 and IEC 60269-3.

This part is not read on its own; it is applied together with IEC 61439-1, which holds the general rules, and it has a Turkish counterpart as TS EN 61439-3. For power assemblies, the separate product part IEC 61439-2 applies.

Key points

1. Covers assemblies operated by ordinary persons: switching operations and replacing fuse-links.
2. Outgoing circuits use protective devices such as IEC 60898-1, IEC 61008/61009, IEC 62606, IEC 62423, IEC 60269-3.
3. Nominal voltage to earth not exceeding 300 V AC; DC limits under consideration.
4. Outgoing circuit rated current Inc <= 125 A; assembly rated current InA <= 250 A.
5. Edition 2 published 26 March 2024 (130 pages); replaces the 2012 edition.
6. Applied with IEC 61439-1; the Turkish counterpart is TS EN 61439-3.
7. Power assemblies are covered separately by IEC 61439-2.

Using it in design

• Board selection rule: allow the DBO type only for office/support-area final boards within the 250 A/125 A limits.
• Specify IT-room boards operated only by skilled persons as PSC (Part 2) or BTS tap-offs.
• State in board specifications which part of IEC 61439 applies.
• Check the voltage limit: applications above 300 V AC to earth fall outside this part.

Who should read it

Electrical design engineers selecting and specifying low-voltage distribution boards.

Related standards

• IEC 61439-1
• IEC 61439-2
• TS EN 61439-3

Publication details

Authors

IEC TC 121

Publisher

IEC

Year

2024

Document number

IEC 61439-3:2024

Document language

English

Source type

Standard

Access

Citation only

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation