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Can a Listed panelboard be retrofitted into an existing cabinet that may be cemented into an existing wall?

Posted By Underwriters Laboratories, Wednesday, March 01, 2006
Updated: Tuesday, February 12, 2013

Question: Retrofitted panelboard

Can a Listed panelboard be retrofitted into an existing cabinet that may be cemented into an existing wall? What additional things need to be considered for the installation?


Panelboards are Listed under the category Panelboards (QEUY) located on page 92 in the 2005 UL General Information Directory for Electrical Equipment, the White Book. The Guide Information for QEUY states panelboards are intended for mounting in cabinets or cutout boxes, which may be provided with the panel or provided separately. Only panelboards marked to indicate that they are for use in a specific box and panelboards labeled as ‘‘Enclosed Panelboards’’ have been investigated to determine that box wiring space is adequate.

When updating an installation where the enclosure has been installed for many years, most likely the enclosure identified on the Listed panelboard is not the enclosure that is already installed. In such situations, installation into the existing enclosure is permissible; however, the AHJ will need to determine if the box wiring space is adequate for the installation. In addition, panelboards marked with short circuit ratings above 10,000 amperes are marked to identify the specific enclosure that must be used to achieve that rating. Panelboards not marked for use in specific enclosures, or panelboards installed into an enclosure other than that identified on the Listed panelboard, revert to a short-circuit current rating of 10,000 AIC. If necessary, UL can perform a Field Evaluation to determine a short-circuit rating above 10,000 AIC for panelboards mounted into enclosures other than is marked on the panelboard. For more information on initiating a Field Evaluation, please contact UL Field Evaluations at call 1-877-854-3577 and select prompt number 2.

Tags:  March-April 2006  UL Question Corner 

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