Almost every tender for an LT panel now asks for compliance with IEC 61439. Many quotes say “IEC 61439 certified” in one line and leave it there. This article explains what the standard actually asks for, so you can tell a verified panel from a panel that only claims it.
Why the Standard Changed
IEC 61439 replaced the older IEC 60439. The old standard sorted panels into Type Tested Assemblies (TTA) and Partially Type Tested Assemblies (PTTA). In practice, “partially type tested” became a grey area: a panel could carry the label with very little proof behind it.
IEC 61439 removed that grey area. Every assembly now needs two things:
- Design Verification, done once for the design.
- Routine Verification, done on every panel before it leaves the factory.
The Parts You Will Meet
IEC 61439 is a family of standards. Part 1 sets the general rules, and the other parts apply them to a type of assembly:
| Part | What It Covers |
|---|---|
| IEC 61439-1 | General rules for all low-voltage assemblies |
| IEC 61439-2 | Power Switchgear and Controlgear Assemblies: PCC, MCC and similar panels |
| IEC 61439-3 | Distribution Boards operated by ordinary persons |
| IEC 61439-6 | Busbar Trunking Systems |
For an industrial PCC or MCC, the two that matter are Part 1 and Part 2, which is why you will see “IEC 61439-1 and 61439-2” on a compliant panel.
Two Roles: Original Manufacturer and Assembly Manufacturer
The standard separates two jobs:
- The Original Manufacturer designs the panel system and is responsible for its Design Verification.
- The Assembly Manufacturer builds a panel to that verified design and carries out the Routine Verification.
They can be the same company, or two. When we build Lauritz Knudsen Enersys panels, Lauritz Knudsen is the original manufacturer of the Enersys system, and we build each panel to the Enersys design.
Design Verification: Proving the Design
Design verification shows that the design meets the standard. It can be done by testing, by comparison with a verified reference design, or by assessment, depending on the characteristic. It covers, among others:
- Temperature Rise: the panel carries its rated current without overheating.
- Short-Circuit Withstand Strength: busbars and supports survive a fault at the rated level, for example a stated kA for 1 second.
- Dielectric Properties: insulation withstands the test voltages.
- Clearances and Creepage Distances between live parts.
- Protection Against Electric Shock and the integrity of the protective circuits.
- Degree of Protection (IP) of the enclosure.
- Strength of Materials and Parts, including corrosion resistance.
- Mechanical Operation of doors, withdrawable parts and interlocks.
Temperature rise and short-circuit strength are the two that matter most in service, and the two hardest to prove without testing. Ask how they were verified.
Routine Verification: Checking Every Panel
Design verification proves the design. Routine verification proves that this panel was built to it. It is done on every panel and includes checks on:
- Wiring, connections and correct fitting of components
- Clearances, creepage distances and degree of protection
- Continuity of the protective circuits
- Dielectric test
- Mechanical operation and interlocks
- Functional checks of control circuits
At Simplex, a test report is handed over with each panel.
Forms of Separation
IEC 61439-2 also describes Forms of Separation: how the inside of a panel is divided by barriers or partitions.
| Form | What Is Separated |
|---|---|
| Form 1 | No internal separation |
| Form 2 | Busbars separated from the functional units |
| Form 3 | As Form 2, and each functional unit separated from the others |
| Form 4 | As Form 3, and the outgoing terminals of each unit separated as well |
Forms 2, 3 and 4 have sub-types “a” and “b”, depending on how the terminals are treated. A higher form costs more, but it makes it easier and safer to work on one feeder while the rest of the board stays in service, always under your site’s own safety rules.
What to Ask Your Panel Builder
Before you place an order, ask for:
- Evidence of Design Verification for the ratings you need: rated current and short-circuit level in kA for 1 second.
- Confirmation that the switchgear matches the verified design: the same make and type of breakers and components that were verified.
- The Routine Verification report for your panel, handed over with it.
- The Form of Separation and IP rating written into the offer.
- Internal arc performance, if your site needs it. This is covered by a separate document, IEC TR 61641, not by IEC 61439 itself.
If a supplier can answer all five clearly, you are buying a verified panel, not just a label.
