UL Question Corner

UL Question Corner: Field modifications of UL Certified (Listed) products, tapping busbars in switchboards, and who is authorized to apply UL Field Evaluation labels

Q. When a UL Certified (Listed) product leaves the factory, the UL Mark on the product is the manufacturer’s attestation that the product complied with UL’s requirements at the time of manufacture. If that product is modified after it leaves the factory, only a UL Field Evaluation can determine if the modified product complies with UL’s requirements.

A. It is the responsibility of the authority having jurisdiction (AHJ) to determine whether any modifications are significant enough to require a UL staff member to evaluate the modified product. UL can assist the AHJ in making that determination.

UL does authorize some field modifications of products, as noted in specific replacement markings appearing on a product. For example, a switchboard may have specific ground bar kits added in the field. The switchboard is marked with a list of field installable accessory kits that have been specifically investigated for use in that particular switchboard. Only ground bar kits that are included in product markings have been investigated for use within that switchboard.

Another exception is a UL Certified (Listed) switchboard constructed with bus work that includes pre-drilled holes marked “TAP” next to the hole. That marking indicates the holes can be used in conjunction with specific wire connectors identified on the switchboard as a field installed accessory. Any other field modifications to the switchboard’s busbars requires a UL Field Evaluation for UL to determine the product’s compliance with UL’s requirements.

If a UL Certified (Listed) product is modified in the field, and the modification is then evaluated as part of a UL Field Evaluation, and found compliant with UL’s requirements, a UL Field Evaluation Label is applied to the product by UL staff. The UL Field Evaluation Label features a serial number referenced in the report prepared by a UL field engineer as part of the UL Field Evaluation. The report details the scope, investigation results, and specific limitations of the field evaluation and should be considered by AHJs when making their approval decision of the modification. The report is required to be provided to an AHJ, as well as, the party initiating the field evaluation. Only UL staff can apply a UL Field Evaluation Label. The UL Field Evaluation Label for the modifications is in addition to the original UL Certification (Listing) Mark on the product.

Switchboards are Certified (Listed) by UL under the product category Dead-front Switchboards (WEVZ). The UL guide information for WEVZ provides the following guidance on taps under the heading of field terminations:

Switchboards may have terminals or provisions for terminals located on the supply side of the service disconnecting means. These terminals or provisions for terminals are marked “TAP,” and the switchboard is marked to indicate the specific terminals or terminal kits intended to be field installed. The suitability of equipment connected to these taps is to be determined in accordance with NEC® 230.46, 230.82, 690.64(A), 701.11(E) and 705.12 by the AHJ at the final installation.

To view the UL Guide information and Certifications (Listings) for WEVZ, go to UL Product Spec at www.ul.com/productspec; enter WEVZ at the category code search. For more information on tapping busbars in a switchboard, click on the Tapping Busbar link under the heading UL publications on the search results page for WEVZ on UL Product Spec.

For more information on UL field evaluations or to obtain a quote, please contact UL’s Customer Service at 877-854-3577, #2 or www.ul.com/field .

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