I am interested in making a widget to sell, but it will probably have a small market and small volume. At what level of complexity should I consider UL listing (or otherwise certifying) my widget?
I presume that device complexity is the range I should measure the device against to obtain a safety certification. I understand it costs several thousand dollars for such things. For a widget with only a few dollars in parts (off the shelf/eBay prices), and a small market or run, it doesn't make much business sense for sure.
However, in general, what level of complexity should I consider to procure some kind of safety certification?
The particular widget I am thinking of right now is a PCB with connectors and possibly a small 24V to 12V transformer (<100ma). Basically, something that was wirenutted/butt-spliced together will now be more professional looking on a board in a box.
Don't let the example distract you from the overall question though.
Best Answer
Its not about how much you sell or liability (a mark doesn't protect you from anything if you burn someones house down, but a safety mark will help prevent you from making mistakes)
I would also like to mention that there are retail boards that will not sell your product if it doesn't have a UL mark on it.
The short answer is: safety compliance is dependent on the market you are selling in, not the complexity of the design. There are different standards that pertain to industrial, residential and commercial markets. The differences and rules are so broad they cannot be covered in an answer (and I only know about 2% and I don't care to know all the rules, laws and safety regulations. I only want to know about those that pertain to the products I design.)
This means you will need to check the laws of your target market.
For example: if you are selling to a business that is required to follow OSHA safety requirements then they can't use that product if it doesn't have an ETL mark. Some local laws (think fire marshals) also require ETL marks.
Source: Is NRTL (UL) Required by law?
The second thing is you are required by law to make sure your product is in compliance with FCC rules (most other countries have similar rules). If your product is causing noise and a radio operator finds it, you could be fined.
Where I work we usually get our products tested through METLAB or TUV. They also do our FCC testing. We also have a compliance engineer to help us deal with passing our compliance (and save time and money, one of our products was being tested to the wrong standard). If I were you, I would make sure I have a safety and compliance\regulatory consultant help you through the process and check to see if you need testing.
A consultant will also save you money, because they can make sure that your product is being tested to the right standards, unneeded testing gets billed to you and those doing the testing are more than happy to make money.
Preparation before testing also saves you money and time, more testing means less money for you. In the past I have made sure I have more equipment than I need (like EMC control products, Extra power supplies\boards in case one fails and\or multiple units). Make sure all critical components used (usually anything over 60V especially anything that touches AC mains, check with the standards that apply to the product you design) in your product have valid certifications. The distance between high voltage sections of your design needs to clear a certain distance (Creepage and clearance distances) if you bring it onto a PCB. These distances also vary depending on the product (and pollution degree, or environment your product will be exposed to)
Also make sure that you size critical components correctly and you buy from sources that will not obsolete components in your product. For example, if you need different power supply, it means a retest and paying more money.
If you plan on selling in an international market, I would definitely get certified and not have to worry about dealing with issues later.
I would also get testing done if I had AC mains running into my product. There have been times when I have specifically designed products with a DC input so we would only have to do safety testing and FCC compliance and reduce the cost of testing (as AC has another set of requirements and standards to test to).