Understanding and Fulfilling Conditions of Acceptability

Editor’s Note: The paper on which this article is based was originally presented at the 2022 IEEE International Symposium on Product Compliance Engineering (ISPCE), held in San Diego, CA in September 2022. It is reprinted here with the gracious permission of the IEEE. Copyright 2022, IEEE.

Introduction

Third-party safety certification evaluations are offered by many independent national and international independent, third-party safety testing laboratories. Within North America and the focus of this paper, accredited laboratories are referred to as “Nationally Recognized Test Laboratories (NRTL)” ¹.

Selection of a particular third-party independent safety laboratory is by choice. Selection is often based on a variety of business factors including, but not limited to, the test laboratory’s brand recognition, technical capabilities, subject matter expertise in particular product evaluation categories, responsiveness, quality of work, costs, regional location and other factors outside the scope of this paper.

Third-party safety certifications provide an important element in a product development cycle, providing independent and non-biased safety evaluation of products, while benefiting many “softer” ethical balances.

The majority of third-party safety certification product evaluations focus on construction and testing requirements against nationally and/or internationally recognized safety standards. These evaluations focus either on the complete end-product, with the end certification being a “Listed or Certified” product, or component/subassembly evaluation known as a Recognized Component or Certified Component approval.

Components/Subassemblies (Recognized Components)

A recognized component certification is still evaluated against applicable safety standards. It’s important to differentiate that the evaluation and testing approach tends to be more limited. Many of a component’s safety features are based on the intended end-product application where such differences and limitations introduce subtle but important ethical obligations and considerations.

For Recognized Components, an often overlooked end-product design consideration is what’s known as “Conditions of Acceptability” (COA). These are specific end-product application integration, test or other restrictions published in the component/subassembly’s certification test report as issued by the certification laboratory.

Virtually all Recognized Components carry one form or another COAs which must be satisfied in the design of the end-product. Although a responsibility of the third-party safety certification laboratory performing the end-product Listing investigation, the end-product original equipment manufacturer (OEM) is also responsible to assure safety critical component/subassembly level COAs are satisfied in their end-product. This is an obligation to help contribute towards a safe end-product. Like the name implies, it’s a condition of acceptability for safe use of the end‑product.

Recognized Component Conditions of Acceptability – Key Considerations and Differences

End-product developers and OEMs introducing a product to market, especially those new to the field of compliance are often unaware of differences between Listing (end-product) and Recognized Component (component and/or subassembly) certifications. Recognized Components certification reports are exclusively assigned COAs, not found in Listing reports. They are identified and documented in their Recognized Component certification report to cover application specifics that must be included in the end-product’s Listing investigation. This report is accessible to the component/subassembly “Applicant” and generally available upon request from the component/subcomponent supplier, although the certification

report and its COAs may be considered proprietary by the component owning entity.

The responsibilities for identifying and obtaining component level COAs lies between the end-product OEM and Recognized Component supplier. Ability to obtain these important COAs can be accomplished through normal business relationships including considering the use of defining contractual specification obligations in procurement agreements between the end-product OEM and Recognized Component supplier.

Depending on the component specifics, application and particular safety standard, a Recognized Component’s COAs may also be published in a third-party certification safety laboratory’s Recognized Component certification directory, but this is not always the case nor a requirement. The information is also internally available to the third-party end-product Listing certification laboratory if the Recognized Component was certified by the same laboratory performing the end-product Listing investigation.

Ethical Considerations – Why Important?

First and foremost, unlike end-product certification Listings, Recognized Component certifications can vary significantly depending on the desired certification approach desired by the Recognized Component manufacturer and as determined with its certification laboratory. Recognized Component certifications are, by design, not intended to cover all application considerations like an end-product Listing encompasses. The actual safety evaluation program (construction and testing elements) can vary significantly since the components themselves are not considered “complete” or “ready to use” like the Listed end-products utilizing use these components and subassemblies.

A component/subassembly manufacturer and selected third- party certification laboratory have a great deal of flexibilities defining and implementing the Recognized Component construction and testing program elements since its tailored toward integration with other products and operating environments.

Identically functioning components/subassemblies may carry a totally different set of COAs for a variety of reasons, some good, some not so good, potentially impacting ethical considerations and outcomes:

Good reasons:

• Safety critical application needs of anticipated Listed end-product are limited, with little to no risk;
• Primary protective safety features are not primarily provided by the recognized component/subassembly vs. elsewhere in the Listed end-product being investigated;
• Supplier cost savings producing lower cost component/subassembly requiring limited safety features as defined in the intended end-products;
• Knowing the end-product will be evaluated in the design and certification process that accounts for the component/subassembly COAs.

Not so good reasons:

• Component/Subassembly manufacturer seeks a Recognized Component certification mark, knowingly accepting many complicated COAs to reduce their own testing obligations of the Recognized Component. Essentially, passing Recognized Component testing obligations from the Recognized Component supplier to the Listed end-product, potentially adding safety risks to the end-product;
• Component/Subassembly manufacturer is only interested in displaying a Recognition Mark on their component and supporting marketing information/data sheet to satisfy “compliance”, while knowing the certification is at minimum levels;
• Component/Subassembly manufacturer seeks a recognition component evaluation plan that requires the least path of compliance testing by the use of many COAs being passed on to the end-product Listing. This creates significant construction and testing evaluation obligations that must be fulfilled for the Listed end-product OEM.

Ethical Importance of COAs – An Example Component/Subassembly Power Supply

Virtually all recognized component power supplies have COAs ranging from simple considerations to more onerous ones, which depends on the technology, application and the power supply vendor’s integrity itself.

There are “ethical” elements to consider since some suppliers of component power supplies try to substitute COAs in their recognized component power supply certification as a cost-reduced approach to minimize and/or eliminate basic safety certification obligations and/or features. This is sometimes achieved by passing these component manufacturers’ obligations to the end-product OEM, increasing both safety certification construction and testing obligations. In many cases, a power supply can and should provide primary safety protection for the end-product since it is the workhorse of voltage conversion and power transfer capable of providing isolated (and safe) current levels and voltages within the OEM end-product by limiting risk of electrical shock and/or fire hazards.

This clearly simplifies construction and testing obligations of the power supply component itself not to mention cost if such features are not included in the recognized component power supply, transferring this obligation to the unsuspecting end-product manufacturer.

One might argue if this is a deliberate opportunity to cut corners by marketing a very limited safety featured recognized component certified power supply to pass on many of the inherent safety features to an unaware OEM building their end-product.

This may be an ethical compromise since the recognized component power supply is marketed as certified by a third- party, independent safety laboratory, particularly in absence of any differentiation between Listed and being a Recognized Component.

There is no obvious right or wrong answer here since COAs are used to address application integration compliance needs. Determining “goodness” of this approach is beyond scope of this publication but should be considered an owned responsibility of the Recognized Component supplier.

Example: Tying a computing product Recognized Component power supply COAs to ethical obligations

Let’s conclude with a simple, high-level walk-through of a partially framed/enclosed switch mode power supply typically used in computing equipment. For illustration purposes, the power supply includes a battery for certain power failure back- up conditions.

The Recognized Component power supply and OEM end-product computing device are covered by IEC 62368-1, Audio/Video, Information and Communication Technology Equipment – Part 1: Safety Requirements (Edition 3)

For this hypothetical example, four simple COAs (or “Application Considerations as noted earlier) are provided in the power supply’s Recognized Component certification report as follows:

• DC outputs of power supply have not been evaluated for short circuit protection.
• Power supply tested to a maximum internal ambient temperature rating of 30ºC as measured in the power supply, meaning the power supply cannot exceed 30ºC air temperature in its immediate surrounding area where installed in the end-product.
• Open frame rear panels containing AC receptable connector not evaluated as an enclosure.
• A lithium battery is provided for back-up circuits and has not been evaluated.

Both compliance and ethical obligations for the third-party NRTL performing the end-product Listing investigation is well defined, being a required action. Critical recognized component COAs must be verified as a part of the end-product certification evaluation.

The “ethical” question comes into play regarding confirmation of the power supply’s COAs compliance for this particular computing product if the OEM elects not to certify their end-product through a third-party NRTL, or, self-certifies the safety of the computer to various norms and directives in countries that permit these practices.

At the end of the day, all COAs must be satisfied in the end-product. In absence of a third-party safety test lab performing this deliverable, the obligation to satisfy the requirement falls on the OEM. Failure to effectively validate that COAs are being satisfied in the end-product creates compliance gaps that may raise question regarding the overall ethical commitment of the end-product OEM. This is due to the selection of a Recognized Component power supply NOT BEING COMPLETE without COA compliance verification in the OEM’s end-product.

The OEM end-product developer may not always be aware of the component/subassembly COA requirement since its often a subtle requirement, particularly when selecting and qualifying recognized components/subassembly that potentially ignore these important obligations, often occurring in situations where the OEM’s end-product is not certified by a third-party NRTL.

Closing on Power Supply COAs –Why Important From Both a Compliance and Ethical Perspective?

Let’s walk through each of the Recognized Component’s power supply COAs to conclude why compliance of each are critical to the safety of the OEM end-product computer and why failure to comply may lead to both a safety issue and ethical infraction:

COA #1: DC outputs of the power supply have not been evaluated for short circuit protection

Failure to meet: Computer end-product loads fail due to non-limiting shorted power supply output, creating electrical shock risk (if isolation system compromised) or fire condition due to overheating.

COA #2: Power supply tested to a maximum ambient surrounding temperature ambient rating of 30ºC

Failure to meet: Most computing products are rated to 40ºC ambient. With power supply rated to 30ºC surrounding ambient temperature, and, in absence of suitably certified temperature derating curves or other end-product certification testing considerations, a possible fire risk may occur if exceeding the power supply’s rated ambient temperature rating as integrated into the computer.

COA #3: Open frame rear panel containing AC power receptable not evaluated as an enclosure

Failure to meet: If the OEM end-product computer employs the rear panel of the power supply as a part of the overall computer’s enclosure, additional fire or shock hazard risks could be created due to an ineffective power supply panel enclosure.

COA# 4: The lithium battery and back-up circuits have not been evaluated

Failure to meet: Depending on the selected non- rechargeable lithium battery, most recognized component lithium batteries have stringent end-product protective requirements including use of series diodes and/or limiting current resistors. These components help to minimize risk of rupture and/or fire due to charging and/or short circuit reverse polarity requirements. Without such verification, risks may not be mitigated.

Conclusions

Takeaways from this paper underscore importance from a product safety design and ethical obligation to understand, identify, and implement a Recognized Component’s accompanying “Conditions of Acceptability or “Application Considerations” as published in its certification report.

When developing an end-product that integrates Recognized Components, awareness for these important design and ethical compliance obligations should be addressed early in the development process. It should be carefully reviewed between the Recognized Component supplier, the end-product OEM and where end-product Listing is applicable, your third-party certification laboratory of choice, typically being a NRTL if North American based.

These obligations should not be arbitrarily assigned or assumed to any one entity since ownership starts with the OEM developing a product that effectively executes components/subassemblies whose safety critical COAs are carefully evaluated, effectively implemented and verified in the end-product. 

References

Nationally Recognized Test Laboratories, United States Department of Labor.