Is It a Critical Part?

For any alternate component, the main consideration for the Certification Lab is whether
the component was reviewed and tested during the original certification evaluation. This
leads to a review of the Certification report for the overall product. Is the component in
question shown in the list of critical components in the certification report? Is it called out
by manufacturer’s name and part number? If the part is called out by manufacturer and
part number, it means that the component is highly critical and will require a certification
agency engineer to review and consider re-test to determine the acceptability of the new

Testing & Review Not Required:

If the component in question is not called out on the critical component list in the
certification report for the product, you may change the component without further
certification consideration. If the component is shown on the critical component list but
the report does not specify the manufacturer or part number for the component, you can
use the alternate component without notifying the certification agency. The new
component must be rated per the specifications stated in the certification report. The
component will be confirmed to comply with the ratings during your next regular
inspection by the certification agency factory inspector.

Testing Required:

If the initial review of the component determines that the original component was
“reviewed and tested”, the new component must be reviewed and tested in the final
product to confirm acceptability. For example, if the component could affect the input
current or the leakage current or was a measured component during the temperature
test, the affected test(s) would need to be repeated on the full product with the alternate
components installed. This is usually the case for alternate critical components such as
EMI Filters (leakage current), Power Supplies and Motors (accessibility, input current,
temperature, fault conditions). Internal components typically require more re-testing than
external components due to the potential impact on internal product temperatures.

Certification Agency Requirements:

It is important to note that OSHA, the agency that accredits US Certification Laboratories
for UL standards, has updated its policies over the last few years to tighten up
requirements in this area. Labs are now required to clearly address test requirements for
Alternate Components and Alternate Constructions. “Engineering rationale” in lieu of
testing is now highly discouraged for critical components that had an effect on the
original test results. This has greatly reduced the willingness of certification agencies to
add alternate critical components without some testing to justify that decision – this is
especially true for alternate EMI Filters, Power Supplies, and Motors.

Conditions of Acceptability:

All certified “components” have Conditions of Acceptability (CofA’s) in their UL
component certification report that provide guidelines that must be met in the end
product. You must comply with all CofA’s in order for the component to be suitable for
your application. Therefore, you should always request the CofA’s from your vendors
when sourcing components. You will also need to provide these CofA’s to your
Certification Lab so they can confirm the component is suitable for your application. The
CofA review is required of the Certification Agency for alternate components even if
testing is not required. In fact, it is part of the process to determine if tests are required
as there are some certified components with CofA’s that require specific tests on the
component when installed in the end product.

Large Sample Considerations:

For large products, changing a component that requires re-testing may not be worth it
due to the expense and difficulty in sending a sample to the certification lab. In this
situation, you may want to consider these options:

  1. If your product is due for an update to a new edition of the standard, you may wish to
    perform this work at the same time to help justify the cost in sending an entire
  2. A Certification Engineer could visit your facility to witness the tests if you have an
    adequate facility and the necessary test equipment.

  3. A Certification Engineer could visit your facility to witness the tests the next time they
    are in your area – to help reduce costs if you do not mind waiting.

Summary of Alternate Component Considerations:

In summary, the process for determining the suitability of your alternate components
should include:

  • Review the Certification Report to determine if the component in question is on the
    critical component list.
  • If the part is not on the critical component list, you can change it without any
    notification to the certification agency.

  • If the part is on the critical component list by ratings only, you may change it to
    another component that meets the same criteria/ratings specified.

  • If the part is on the critical component list with the manufacturer’s name and part
    number specified, you must request the certification agency add any replacements or
    alternates. This process involves a review of certified component CofA’s and,
    determining if testing on a sample of the overall product incorporating the new
    component(s) is necessary. Certain components are more likely to impact the
    original test results and therefore require re-test. These include EMI filters, Power
    Supplies, Motor Controllers, and Motors.

CertifiGroup can help you determine the suitability of your components
CertifiGroup operates a complete Product Test & Certification Lab

CertifiGroup can certify or field label your products to UL & CSA standards
On-site, at your facility, or in our lab!

Contact us and get help today!

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