National Electrical Installation Standards

Standards as High as Your Own

 
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Monday, July 25, 2022

Question:

Hello CQD,

Thank you for the daily read and your daily work in educating us further and your input is always appreciated. When installing or replacing the screws for a load center cover, if the screws become stripped out in older existing installations when doing service work or have been lost is it a code violation to install a sheet metal screw or a thread forming screw to get the cover installed. The instructions that I have read (SQ D QO) say to install the cover with the screws provided. Most load centers and covers are entirely painted surfaces but it appears the screws that come with the cover might have some bonding capabilities that a substituted screw might not have. Section 110.3(B) requires following the manufacturer’s instructions 250.4(A)(4) and 250.4(B)(4) would require bonding of the cover. 250.8(A)(5)&(6) mention screw thread requirement and 250.12 discusses clean surfaces.

Brian Frion

A

Answer:

Hi Brian,

This particular condition requires the manufacturer to provide a solution that remedies the stripped threads for fastening the cover. One could use a larger thread-forming screw and accomplish the task, but the recommendation and solution should be from the manufacturer so as the meet the 110.3(B) requirements you mention in your question. This is important because the grounding of the cover relies on properly fastening to the panelboard cabinet. Hope this is useful. 

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