IEC 61439 Switchboard Standard Explained for Buyers
An IEC 61439 switchboard is a low-voltage assembly whose ratings have been proved by design verification and whose every unit is checked by routine verification before it leaves the workshop. Part 1 sets general rules and Part 2 covers power switchgear assemblies. The buyer's task is to confirm both verifications exist and match the ratings ordered.
What you receive: send your single-line diagram and fault level, and you receive a written quotation within one working day that states the verified ratings, form of separation and FAT. Request a quotation
By Eng. Babu Parkash, Panel Engineering, Saudi Control Panels Company. Published October 2026.
What is IEC 61439 and what did it replace?
IEC 61439 is the series that sets the rules for low-voltage switchgear and controlgear assemblies up to 1,000 V a.c. It replaced IEC 60439, which divided assemblies into type-tested (TTA) and partially type-tested (PTTA). That split is gone. The current series asks one question of every assembly: can the manufacturer prove each rating it claims?
Two parts matter for most buyers:
- IEC 61439-1 gives the general rules that apply to every assembly.
- IEC 61439-2 adds the requirements for power switchgear and controlgear assemblies, the standard behind main distribution boards, sub-distribution boards and MCC sections.
Other parts cover distribution boards for unskilled operators, busbar trunking and similar products. If a specification only says "IEC 61439", ask which part, because the answer changes the test list.
What is the difference between design verification and routine verification?
Design verification proves the design. Routine verification proves the individual unit. You need evidence of both.
| Point | Design verification | Routine verification |
|---|---|---|
| Done on | The assembly design, once | Every assembly built |
| Who is responsible | The original manufacturer | The assembly manufacturer |
| Methods allowed | Testing, calculation, or design rules | Inspection and test |
| Typical items | Temperature rise, short-circuit withstand, dielectric properties, clearances, IP degree | Wiring and operation, dielectric check, protective circuit continuity, mechanical operation |
| Evidence you receive | Verification summary for the ratings | Signed test record per assembly |
The original manufacturer is whoever carried out the design verification and owns the design. The assembly manufacturer completes a specific board and takes responsibility for it. Both roles can sit in one company, or the assembler may build on a verified system from a component maker and follow its rules exactly. Either route is valid, provided the rules were followed and the record exists.
What data should appear on an IEC 61439 switchboard nameplate?
Look for the rated values, because each one limits what the board may be used for.
- Rated voltages, including operational voltage and insulation voltage.
- Rated current of the assembly (InA), the most the board can carry as a whole.
- Rated short-time withstand current (Icw) with its duration, or the conditional short-circuit rating with the protective device that backs it up.
- Rated diversity factor (RDF), where less than 1.
- Form of separation, from Form 1 to Form 4b.
- Degree of protection, as an IP code under IEC 60529.
- Manufacturer name, date and the standard the assembly follows.
A nameplate without a short-circuit value or an RDF should prompt a question, not a signature on the approval form.
Worked example: reading the rated diversity factor
Worked example: the figures are made up to show the method. A board has InA of 2,500 A. Its outgoing circuits are four of 800 A and six of 250 A.
| Step | Calculation | Result |
|---|---|---|
| Sum of outgoing ratings | 4 × 800 + 6 × 250 | 4,700 A |
| Largest permitted simultaneous load | Cannot exceed InA | 2,500 A |
| Highest RDF that works | 2,500 ÷ 4,700 | 0.53 |
| Verified RDF chosen | Rounded down | 0.5 |
| Simultaneous load the design supports | 0.5 × 4,700 | 2,350 A |
If all ten feeders can run at full load together, an RDF of 0.5 is wrong for the job. You would need a board with a higher InA, or an RDF of 1 with the busbars and incomer sized to match. Raising the RDF raises the busbar section and the temperature-rise margin, which is why the point belongs in the specification, not in the factory.
How does an IEC 61439 switchboard show short-circuit capability?
The board must withstand the fault current at its location for the time the upstream device takes to clear it. Two routes appear on nameplates:
- Icw, the short-time withstand, for example 50 kA for 1 s. It suits boards with an incoming air circuit breaker that can be delayed to coordinate with downstream devices.
- Conditional rating (Icc) with a named short-circuit protective device. It suits boards protected by a current-limiting device upstream.
Ask your design team for the prospective fault level at the board and check the nameplate exceeds it with margin. Our LV switchboards are built to IEC 61439-1 and -2, with short-circuit ratings up to 100 kA depending on the design verification. Details of ranges, forms and ratings are on the LV switchboards and MDB page.
Where does the routine verification happen?
At the workshop, before shipment, as a recorded factory acceptance test. The record shows that the unit you receive matches the design that was verified. Our factory acceptance test follows IEC 61439 routine verification and is included in the price, with customer or third-party witness welcome. The sequence is covered in the panel FAT and testing page, and if the design itself is still open, the panel design and drawings service fixes the ratings before the build.
Questions about the IEC 61439 switchboard standard
What is an LV panel?
An LV panel is an assembly of switchgear, protection and metering rated up to 1,000 V a.c., used to distribute or control power in a building or plant. Main distribution boards, sub-distribution boards and motor control centres are all LV panels.
Is IEC 61439 mandatory in Saudi Arabia?
Project specifications and end-client standards normally call for it, so in practice most industrial buyers require it. Check the specification of your project, because it will name the parts and any additional client standard that apply.
What is the difference between IEC 61439 and IEC 60439?
IEC 60439 split assemblies into type-tested and partially type-tested. IEC 61439 replaced that split with design verification by testing, calculation or design rules, plus routine verification of each unit. Requests that still quote TTA or PTTA are working from the older text.
Can a board be built to IEC 61439 without a type test?
Yes. The standard accepts design verification by calculation or by design rules, not only by testing, provided the original manufacturer follows the permitted method and keeps the record. What matters to the buyer is that the record exists and matches the ratings.
How quickly can a verified quotation be issued?
We issue a quotation within one working day of receiving your single-line diagram, stating the verified ratings, form of separation and FAT scope so that you can compare it with other offers.
Need an IEC 61439 switchboard specified correctly the first time? Send your single-line diagram and fault level, and we will return verified ratings, a form of separation and a lead time within one working day.