A specification that asks for a “type-tested assembly” is asking for something IEC 61439 stopped calling by that name in 2011. The vocabulary matters, because what the manufacturer owes you under the current edition is both broader and narrower than the phrase suggests.
IEC 61439-1 is in its third edition, published on 5 May 2020, and IEC 61439-2 followed on 22 July 2020. Both replaced 2011 second editions. Most specifications circulating in the Kingdom still quote the 2011 text, and a good number still quote IEC 60439, which the 61439 series replaced outright. None of that is fatal — but it changes what a verification report has to contain, so the first question on any assembly is which edition the report was written against.
Verification replaced testing, and that was deliberate
Under the old series, a design was proved by testing a sample. Under 61439 it is proved by design verification, and testing is only one of three routes the standard allows. The other two are verification by calculation or measurement, and verification by satisfying design rules. For some characteristics all three routes are open; for others only testing will do.
This is not a loophole. It is how a manufacturer can offer a range of arrangements without building and destroying every one of them, and the standard is specific about which route is permitted for which characteristic. The practical consequence for a buyer is that “verified” does not mean “tested”, and a report that says verified by calculation against a clause where calculation is permitted is fully compliant. Rejecting it on sight is a common and expensive mistake in technical evaluation.
The nineteen verifications
Part 1 sets out the design verifications by clause. An assembly is not verified in general; it is verified against each of these, and a report should be readable against the list.
| Clause | Verification |
|---|---|
| 10.2.2 | Resistance to corrosion |
| 10.2.3.2 | Strength against abnormal heat and fire |
| 10.2.4 | Resistance to UV radiation |
| 10.2.5 | Lifting |
| 10.2.6 | Mechanical impact |
| 10.2.7 | Marking |
| 10.3 | Degree of protection of enclosures |
| 10.4 | Clearances and creepage distances |
| 10.5.2 | Continuity of the protective circuit |
| 10.5.3 | Short-circuit withstand of the protective circuit |
| 10.6 | Incorporation of equipment |
| 10.7 | Internal electric circuits and connections |
| 10.8 | Terminals for external conductors |
| 10.9.2 | Power-frequency withstand voltage |
| 10.9.3 | Impulse withstand voltage |
| 10.10 | Temperature rise |
| 10.11 | Short-circuit withstand strength |
| 10.12 | Electromagnetic compatibility |
| 10.13 | Mechanical operation |
The three clauses that get misread
10.10, temperature rise. The verification is not an absolute statement of current-carrying capacity. It is a statement about rise above a reference ambient, under a declared loading pattern. Edition 3 introduced a group rated current for circuits within a loaded assembly and refocused temperature-rise verification on it; the assumed loading of Part 2 remains the basis most specifications still quote. Either way, a 4000 A board is 4000 A under the conditions on the certificate, and the conditions are on the certificate for a reason. The companion piece on ambient derating takes this apart in detail.
10.11, short-circuit withstand strength. Two different declarations live under this clause and they are not equivalent. Rated short-time withstand current, Icw, says the assembly survives a defined current for a defined time — typically 1 s — with no device clearing it. Conditional rated short-circuit current says the assembly survives only because a named protective device, with a named let-through, clears the fault first. The second is perfectly legitimate and often the right engineering answer. It is also device-specific: change the incoming breaker on site and the declaration no longer applies to the board in front of you.
The manufacturer is not the brand on the enclosure. The standard distinguishes the original manufacturer, who establishes the verified design, from the assembly manufacturer, who builds the finished assembly and is responsible for it. A certificate showing that an enclosure system was verified by its originator is evidence about the system, not about the board. The assembly manufacturer must stay inside the verified arrangement, and must say so. Ask whose name is on the declaration of conformity, and whether the arrangement supplied falls inside the verified envelope — busbar supports, ventilation, device positions and cable entries are all part of that envelope.
What to ask for, in this order
| Ask for | What it tells you |
|---|---|
| The edition the report is written against | Whether you are comparing like with like across bids |
| The verification route used for each clause | Where testing was done and where calculation or design rules were applied |
| The declared ambient and loading behind clause 10.10 | Whether the rating survives your switchroom |
| Whether 10.11 is Icw or conditional, and on which device | Whether a device substitution invalidates the rating |
| The name on the declaration of conformity | Who carries responsibility for the assembly you receive |
| The routine verification record for your serial numbers | That the evidence is about your boards, not a design |
Where we stand
Our low voltage assemblies are built inside verified designs and routine verification is recorded per assembly, against the serial numbers on the boards. The verification route is stated clause by clause rather than summarized, and both the design verification evidence and the routine verification record for a named order are issued on request against a technical enquiry. The documentation register lists the standards with their references and validity.