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We have a product, and we're trying to get it MET marked for export from the UK to the US. It uses an APD S10 converter [datasheet] to generate +-250V rails from a 12V supply. It's an isolated converter, but we're not using it as such, we've tied the negative input and the centre output together.

The relevant standard for our product is EN61010. Since the converter is not bridging an isolation barrier, I assumed that the only relevant part would be the flammability requirements. APD can provide us with datasheets showing V0 flamability for the PCB and potting compound, and the whole thing is in a metal case, so that seemed sufficient. And initially the test house agreed.

The test house has now changed their mind. Apparently MET labs think the converter should be tested separately to EN 60950. This seems like a sensible choice of standard, but the converter does not have a UL number and has not been tested. The manufacturer says the norm is to just test it as part of a complete product, in the same way the rest of the circuit is tested. I realise we'd be better off with a UL recognised converter, but there aren't many at the right voltage and it's too late to change - we've already passed EMC tests with this one, and we need to ship ASAP.

What am I missing here? What is the norm? APD is an American company, serving an American market, so there must be some way for them to sell these non-UL-recognised components for inclusion in a UL listed product. But now MET seem to be telling our test house that that is not possible. Yet APD are telling me that it happens all the time. I feel like I'm in the middle of a game of Chinese whispers, and want to understand the American system better.

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    \$\begingroup\$ The norm that I've always done is to get parts that do the job, and get the full product to pass the various tests and standards. Include a non-UL component is fine, as long as your product as a whole is UL complaint. \$\endgroup\$ – Puffafish Jun 29 '17 at 10:55
  • \$\begingroup\$ Yeah, that's kinda how I've approached this. But how do I demonstrate the whole product is compliant? An example or two of how you've done that with non-UL components would be awesome. \$\endgroup\$ – Jack B Jun 29 '17 at 10:59
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    \$\begingroup\$ Maybe I'm missing sth, but having a quick look at the datasheet you provided I found this at the last section: "The converters are designed to meet North American and International safety regulatory requirements per UL 60950- 1/CSA 22.2 No. 60950-1-07 Second Edition, IEC 60950-1: 2005, and EN 60950-1:2006." Isn't this that you want? The UL 60950? \$\endgroup\$ – nickagian Jun 29 '17 at 11:13
  • \$\begingroup\$ @nickagian I thought so, but after including them in my design, testing, paying for EMC testing etc., I discovered that "designed to meet" doesn't mean "meets, tested to, and UL recognised". \$\endgroup\$ – Jack B Jun 29 '17 at 11:16
  • \$\begingroup\$ Oh my god!! Really? I wouldn't expect sth like this! I may have to reconsider my way of thinking in the future, since I normally trust what it is written on the datasheet... Unfortunately I cannot give much help for your actual problem. Until now it didn't happen to me to have a non certified component. But I think our test house also examines some critical components of the product (such as a converter like yours) separately. \$\endgroup\$ – nickagian Jun 29 '17 at 11:55
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we need to ship ASAP ... What am I missing here?

Someone that understands the certification process. If you had such a person, they would have been involved from the start, and not allowed you to leave certification as something to do at the end. Thinking "We'll ship next week, just got to get this thing certified" shows extreme naivety to the point of incompetence.

Uncertified components

Ultimately, you want your whole product certified. That can be quicker and easier if whole subsystems are already individually certified. Your test house then can treat the subsystems as black boxes and not look inside. If a subsystem is not separately certified, then they have to look inside. This takes more time and therefore costs more, but does not by itself mean your whole unit can't be certified.

If you do go thru this process, it will cost less to get another product certified that uses whole subsystems from this one. It is quite possible that the same testing house has already done this with your exact subsystems for another customer. That will save them money, but they'll never tell you that. From your point of view, if ADP won't provide a certification, then your test house will have to look inside that module enough to prove to themselves that it meets all relevant requirements for how you are using it.

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    \$\begingroup\$ OK, just to clear something up on the incompetence front: I am based in the UK and the converters are OK for UK (CE) marking. We just have to do flammability as I said. Early in the process I phoned APD and described our use case. They said that UL approval was not a problem, lots of US customers use it the way we want. I then phoned our UK test house, who work with MET, and they said it was fine. I phoned a MET examiner in the UK and they said it was fine. This was 6 months ago. Now it's not fine, and I'm trying to work out why. But we're not here because I left it to the last minute. \$\endgroup\$ – Jack B Jun 29 '17 at 11:24
  • \$\begingroup\$ @Jack: Apparently "MET" is a test house. There are many out there. Maybe you need to use a different one if this one is giving you a run-around. \$\endgroup\$ – Olin Lathrop Jun 29 '17 at 11:26
  • \$\begingroup\$ Perhaps. We paid up front, which we're going to regret if we do that... I'd like to be confident that option was going to work before we jump into it (hence this question). If you have anything to add on the "relevant requirements for how you are using it" front, based on my description, that would be appreciated (I can edit in more details if that is useful) \$\endgroup\$ – Jack B Jun 29 '17 at 11:29
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You may wish to consider talking with your converter supplier about sharing in the cost of obtaining UL certification for the converter. The testing regime will be about equal but it is a win-win scenario.

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First on all, it is important to consider that UL listing is not a matter of matter of submitting, passing, done. To manufacture items with a UL mark, UL will review the manufacturing plant and its quality assurance system. You must sign a contract that must be in force for as you as you are manufacturing items with a UL mark. You must agree to ongoing unannounced UL inspections. Many manufacturers have one of their own engineers assigned to assuring UL requirements are met.

Many complex products contain some components that are not UL recognized. UL will review the risk of failure of those components, possible failure modes and the risk of fire, electric shock or other safety issues. They are concerned only with safety not with products meeting any performance standards. If a US company that wants to incorporate your product in a UL listed product, they may very well have reason to be confident that is manageable without your product being recognized. Other potential US customers may have a different view. To some extent it depends on their relationship with UL. If the UL inspector knows a company has reliable people of their own assuring the maintenance of UL standards, tow whole process is easier and less expensive.

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