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AS/NZS 3000 specifies the electrical installation safety requirements for all premises in Australia and New Zealand. Following a 5-year transition period from 2016, the release of ‘AS/NZS 3000 Amendment 2’ mandates from May 2021 the AS/NZS 61439 series of standards for switchboard assemblies, superseding AS/NZS 3439. This change will impact the design and modification of electrical distribution, mechanical services, and other switchboards in buildings.
In Australia, the design and construction of switchboard assemblies not exceeding 1,000 V a.c. or 1,500 V d.c. previously followed AS/NZS 3439. This standard provided guidelines for the manufacture, testing and certification of all low voltage switchgear and the associated control gear assemblies.
Upgrades from AS/NZS 3439 to AS/NZS 61439 include:
- Definitions for Type-tested assembly (TTA), and Partially Type-tested assembly (PTTA) now replaced with “Design Verification”.
- Temperature rise verification by calculation now restricted to 630A (single compartments) and 1600A for Complete Board.
- Deviations from Original Manufacturer documentation means the Assembly Manufacturer becomes responsible for all Design Verification.
- Clients accepting switchboards without Design Verification will be legally responsible for the board.
Upgrades to existing switchboards built to previous standards are now more onerous. Replacing like-for-like components replacement is permitted, but changes to the switchboard itself results in upgrades to the section, which is practically an upgrade to the switchboard.
The Design Verification process listed in the standard highlights key components to be conformed with, including:
- Strength of materials and parts
- Insulation properties
- Protection of electric shock
- Integrity of protective circuits
Temperature Rise Calculations consider elements within the assembly, such as busbars and functional units, which need to be designed to withstand required operating conditions. Temperature calculations to comply with temperature limits are now provided with additional information on applied rated diversity factors.
Arc fault containment remains an optional component of the standard and a comprehensive list of common risks are identified including possible causes of failures within switchboards. Key components at risk due to incorrect or no maintenance are listed as common causes, with highlighted risks including:
- Damaged Insulation
- Incorrect installation of protection devices
- Replacement of protection devices with an inappropriate one
- Substitution of components not meeting the same standard or performance
- Inadequate protection barriers
AS/NZS 61439 includes a number of parts which are already published and applied. These being Part 0 – Guide to specifying assemblies, Part 1 – General Rules and Part 2 – Power Switchgear and Controlgear. It is of note that Part 3 – 6 detailing requirements for distribution boards, assemblies for construction sites or power distribution and busduct systems are proposed to be included within the AS 61439 series, superseding the international standard IEC 60439.
AS/NZS 3000 Amendment 2 provides further guidance to the industry on the introduction and application of the AS/NZS 61439 standard. The amendment also details circumstances where a switchboard does not require Design Verification to
AS/NZS 61439 including:
- Total connected load exceeds 125 amps per phase or,
- Prospective short-circuit current at the switchboard is greater than 10 kA
In these instances, independently verified assemblies can be achieved relying on manufactures component assessment and certification.
The AS/NZS 61439 Low-voltage Switchgear and Controlgear Assemblies standard and Amendments to the Wiring Rules can be obtained from SAI Global at https://infostore.saiglobal.com/
For guidance on design, modification, operation, maintenance and management of electrical infrastructure within facilities contact:
John Topouzakis
Discipline Leader (Electrical), A.G. Coombs Advisory
P: +61 3 9248 2700 | E: jtopouzakis@agcoombs.com.au
