I'm designing a circuit board for a large industrial product which is intended to be UL certified, so the boss wants as many individual submodules to be UL certified as possible, including mine. The problem is, certification seems to be an impenetrable maze for someone who isn't an expert or doesn't have significant experience; every standard is locked behind a paywall, and there are no clear guides to which standards a given product even needs to meet in the first place. CE isn't quite as bad, a bit of googling tells me as long as my board is safe and doesn't put out much EMI, I should be good.

The board is a Power-over-Ethernet PD, the sole function of which is driving some stepper motors. I'm just trying to get some idea of what I need to take into account when designing the thing to give it a decent chance of passing certification.

In general, how is someone starting any new design supposed to find out what they need to take into account without paying large sums of money?

  • 1
    \$\begingroup\$ Many UL specs have IEC equivalents that are cheaper to purchase. But knowing which specs you need to meet is the first battle. If you don't have an in-house expert, you may need to hire an outside consultant to guide you through it. \$\endgroup\$
    – The Photon
    Nov 20, 2019 at 20:59
  • \$\begingroup\$ Do you have access to a library that has the standards available? \$\endgroup\$ Nov 20, 2019 at 21:01
  • \$\begingroup\$ @ThePhoton that is what we're looking at, it just seems like a rather large expense for this early in the process \$\endgroup\$ Nov 20, 2019 at 21:02
  • \$\begingroup\$ @SpehroPefhany I don't believe so \$\endgroup\$ Nov 20, 2019 at 21:02
  • 2
    \$\begingroup\$ Maybe your boss will change his mind when s/he sees the price tag. Or maybe s/he'll realize it's less cost to do it right the first time than to try to fix it later. \$\endgroup\$
    – The Photon
    Nov 20, 2019 at 21:03

1 Answer 1


As an example UL 1449 editions 3 and 4 cover industrial and residential surge suppression devices in the USA. Because of hazards they must be under UL and ISO regulations. In this case UL is about technical details and using UL approved parts such as X and Y rated capacitors for line to neutral and neutral to ground filtering. RoHS standards require lead-free solder.

ISO is more about documentation of both devices and the equipment used to test them. Then you have documentation about the documentation under a document control supervisor. It will drive you bonkers to implement this.

I would say to contact UL, FCC and ISO to find out if your product is under agency control of any kind. RF emitting devices have to follow FCC guidelines such that the container limits emissions to a stated level.

An exception would be DIY stuff not directly line connected and not emitting any radiation or RF noise or high voltage (shock hazard) or high current (burn hazard). But if you build and ship in large quantities it would behove you to analyse what the dangers are and any emissions and put a disclaimer on the product. Labels are a form of self-disclaimer such as "HIGH VOLTAGE", "SHOCK HAZARD" and "BURN HAZARD". This can fend off malpractice attorneys who would tear you to pieces if someone was injured by your product. By the way surge suppression devices must have all of the above labels and disclaimers about miss-use of product.

Before building anything for mass shipping I would get in touch with an attorney who can hire a pion to look into the myriad things that can bite you later on. You seriously need to get your ducks in a row before you ship anything that you or your employees built. Manufacturing can be an expensive business with lots of up-front cost, so consider the legal research worth it.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.