Buying LV switchboards from China: IEC 61439 design verification, routine verification and device changes

This guide covers low-voltage switchgear and controlgear assemblies (main switchboards, sub-distribution boards and motor control centres) bought from Chinese panel builders for buildings, industrial plants, infrastructure and energy projects. Sinospect checked the standards and rules below at their sources on 26 September 2026.

The IEC 61439 series

IEC 61439 covers assemblies rated up to 1,000 V AC or 1,500 V DC. Part 1 sets the general rules and applies together with the part for the type of assembly. Main switchboards and motor control centres are power switchgear and controlgear assemblies (PSC-assemblies) under Part 2, which also covers any assembly the later parts leave out.

The 2020 editions introduced a group rated current (Ing) for circuits loaded together, and temperature-rise verification now centres on it. They added requirements for DC and the concept of class I and class II assemblies. IEC 61439-2:2020 clarified the forms of internal separation: above Form 1, the parts inside a functional unit’s compartment that stay live when the unit is switched off are protected to at least IPXXB. Since March 2026, assemblies for photovoltaic installations have their own part, IEC 61439-8.

IEC 61439 replaced the IEC 60439 series and its type-tested (TTA) and partially type-tested (PTTA) assemblies; ABB’s 2010 guide to the change gave 2014 as the end of the overlap. An offer that cites IEC 60439, TTA or PTTA refers to that earlier scheme.

Two stages of proof

IEC 61439 sets two stages of proof for a switchboard. Design verification is made once, on the design, by the original manufacturer: the organisation that designed the assembly system and verified it. Routine verification is made on every switchboard by the assembly manufacturer, the panel builder that builds it and takes responsibility for it. The standard provides for assemblies built by a company other than the original manufacturer.

For each characteristic, IEC 61439-1 allows verification by test, by comparison with a tested reference design, or by assessment through calculations and design rules, in the combinations below.

A change of device make or busbar layout

ABB’s guide to the standard states the rule for changes: a panel builder that adds arrangements outside the original manufacturer’s verification is deemed to be the original manufacturer for them, and verifies their design.

Device substitution has limits of its own, which BEAMA’s guide to verification sets out for the current edition. For temperature rise, a device from another series or another make can replace a verified one on the strength of the original test, under strict design rules: the physical arrangement stays essentially the same, and the substitute’s power loss and terminal temperature rise, tested to its own product standard, are equal to or lower than the original’s. For short-circuit strength, the comparison checklist of IEC 61439-1 (Table 13) keeps to devices of the same make, unless the circuit is exempt from short-circuit verification under 10.11.2.

A Chinese offer that changes the circuit-breaker make named in the specification, or the busbar layout, therefore comes with verification evidence for that change.

Routine verification before shipment

Routine verification is made on every switchboard. It covers the degree of protection, clearances and creepage distances, protection against electric shock and the continuity of protective circuits, the built-in components, internal circuits and connections, terminals for external conductors, mechanical operation, dielectric properties, and wiring, operational performance and function. The factory acceptance test lets the buyer witness it before shipment: see switchgear and control panel FAT witnessing.

In China: GB/T 7251, CCC and cabinet families

China’s GB/T 7251.1-2023 and GB/T 7251.2-2023, in force since 1 March 2024, are identical adoptions of IEC 61439-1:2020 and IEC 61439-2:2020. They replaced the 2013 editions, which adopted the 2011 IEC texts; Part 2 moved from number GB/T 7251.12 to GB/T 7251.2. The 2013 general rules had in turn replaced GB 7251.1-2005, China’s standard for type-tested and partially type-tested assemblies.

Power switchgear and controlgear assemblies sold in China need China Compulsory Certification (CCC). Since the certification authority’s announcement of November 2023, the CCC reference standard for them is GB/T 7251.2.

Chinese makers sell switchboards under family names: GGD for fixed boards, and GCK, GCS or MNS for withdrawable (drawer) designs. IEC 61439-2 describes the same choice with its own codes for how functional units connect: F for fixed, D for disconnectable and W for withdrawable. The specification states the code and the form of separation; the offer names the family and the design verification behind it.

What the specification and the offer state

IEC 61439-2 lists in its Annex AA the items the user and the panel builder agree on, with a default for each item the specification leaves open: the earthing system, the nominal voltage, the form of separation (Form 1 to Form 4b), how functional units connect (F, D or W), the degree of protection and more. IEC TR 61439-0 guides the specifier through them. The offer answers with the ratings:

• rated voltage (Un) and rated impulse withstand voltage (Uimp);
• rated current of the assembly (InA), and the rated current (Inc) and group rated current (Ing) of the main circuits;
• rated short-time withstand current (Icw) and rated peak withstand current (Ipk), or the rated conditional short-circuit current (Icc) with its protective device;
• the rated diversity factor (RDF) where the design uses one;
• the form of separation, the F, D or W code and the degree of protection (IP).

What moves the price and the lead time

• the rated currents and the short-circuit level;
• the form of separation and fixed or withdrawable functional units;
• the device makes named in the specification, and the design verification that covers them;
• busbar material and size;
• the degree of protection and the enclosure;
• metering, communication and control wiring;
• the test regime: routine verification witnessed at the factory;
• documentation, packing and the delivery term.

A BOQ that lists these per switchboard gets quotations that can be compared line by line: see preparing a BOQ or specification.

Buyer checklist

Before award

• IEC 61439-1 and IEC 61439-2 named with their 2020 editions, or GB/T 7251.1-2023 and GB/T 7251.2-2023, with the Annex AA items filled in.
• Ratings: InA, Inc and Ing, Icw and Ipk or Icc, the form of separation and the F, D or W code.
• Design verification records for the configuration quoted: the method for each characteristic, the reference design, and test reports with laboratory, date and edition.
• The device makes and busbar layout those records cover, and verification evidence for any change.
• Where the maker cites a CCC certificate: the models and ratings it covers.

Before shipment

• Routine verification records for each switchboard.
• The factory acceptance test witnessed where the contract provides for it.
• Drawings, wiring diagrams, manuals and the spare parts list in the destination language.

Frequently asked questions

Sources

Checked at the sources on 26 September 2026.

• IEC: IEC 61439-1:2020, IEC 61439-2:2020, IEC 61439-3:2024, IEC 61439-4:2023, IEC 61439-5:2023, IEC 61439-6:2012, IEC 61439-7:2022, IEC 61439-8:2026, IEC TR 61439-0:2022, IEC 61439-1:2020 preview (contents, foreword, scope), IEC 61439-2:2020 preview (contents, foreword)
• Guides: BEAMA, guide to verification of PSC-assemblies to BS EN IEC 61439-2:2021 (July 2023), ABB, IEC 61439: the new standard for low-voltage switchgear and controlgear assemblies (2010)
• China: GB/T 7251.1-2023, GB/T 7251.2-2023, GB/T 7251.1-2013 (China’s national standards portal), CNCA announcement 2023 No. 24
• Makers’ pages on cabinet families: Tongmai Electric, Zhongze Electric