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What is needed for UL ?

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What is needed for UL ? | 6 August, 2017

We have a client that wants to export modules to the USA, which they didn't do so far, and ask for UL status.

I am a bit unclear about that, so I wonder what is needed?

For the PCB it's clear, must be from a UL supplier. Does the UL number has to be on the PCB?

How about other components, do all parts, (R, C, IC, connectors etc) must be from a UL supplier? (I guess so)

Must cables/insulated wires have the UL logo? (I have some AWG28 cables on the board)

I hope somebody can help with some answers.

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What is needed for UL ? | 7 August, 2017

The only people that can answer what you need is UL.

At least once a year an inspector from UL stops by and makes sure the High-Pot tester is up to date on calibration and that we are following the BOM provided by the customer and approved by UL.

At at previous company the UL inspector showed up and informed us that we were putting the wrong parts on. They were the parts provided by the customer.

Specific requirements will depend on the product.

Who will be paying for the inspections, you or your client?

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What is needed for UL ? | 8 August, 2017


What is needed for UL ? | 10 August, 2017

> The only people that can answer what you need is UL.

I worked with VDE and I do not know any company that works like that. With VDE we prepare a module according to VDE standard and do an internal pre-approval - and present it.

To put something randomly together and send it to UL will extend the time and the cost.

Looks like some parts have no UL requirement, can't see any for 'normal' Yageo R and C.

So back to square one, do all parts need UL?

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What is needed for UL ? | 10 August, 2017

Do not put something randomly together. Go to the UL web site. Ask them your questions. Do not only ask us. Personally I think you would be smart to present the BOM to UL before buying anything. And parts being UL is not the only requirement.

Where did you get the VDE standards from?

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What is needed for UL ? | 31 August, 2017

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What is needed for UL ? | 8 September, 2017

UL listing is handled by the customer typically. I am assuming you are a contract manufacturer producing only a component pcb assembly for use in a product final assembly and not the final product itself. We are a manufacturer that does our own population now, but previously we designed and had our UL listed products' pcba's made by a third party. We (the customer) were wholly responsible for designing and getting the product to pass UL's tests as a completed assembly. A UL inspector comes to our facility quarterly for construction review for proper components and hipot calibration and operation, etc. UL does not care who does the population of the PCB, just that it matches the listing report for construction. However, if you are manufacturing completed assemblies with a UL mark that you are applying, you definitely will need to be the manufacturer getting the UL listing. If that is the case, contact UL.

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What is needed for UL ? | 11 September, 2017

Great reply, Tom.

We do contract assembly of a few UL listed products and when we do, the customer has always done the legwork up front, with UL, to determine which components are critical.

Being the manufacturer of record, we're responsible for making sure we purchase per the UL requirements and maintain the proper records.

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What is needed for UL ? | 12 September, 2017

My experience with UL is that they are mainly concerned with fire and shock to the user. They are usually not concerned about products that are under 50 Volts.

UL recognition is different than UL listing. UL listing is for a completed system (this is the UL with a circle around it). The system may contain UL recognized components, usually indicated with a backwards UR.

It starts with design. The board may have required electrical clearances between high voltage (>50) traces. The design will be tested for safety and a file will be created listing all the critical components such as transformers, relays, wiring, enclosure material, etc.

On the manufacturing side, a manufacturing facility must be indicated in the UL file and an inspector will periodically check that the critical components listed in the UL file are actually being used. They may also check some equipment calibration such as a hipot tester.

The PCB vendor will mark the board with their UL recognized logo, not the UL number. Usually a 94V-0 will indicate flame retardant properties.

R, C, IC, etc. are not required to be UL unless they are very specialized. Usually it is switches, relays, transformers, some connectors and wiring that must be UL recognized.

Wiring should not be required unless it is high voltage.

Hope this helps.

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