Prefabrication is becoming more popular for electrical contractors as an effective way to improve quality control and worker safety while remaining competitive in electrical construction. This article focuses on prefabrication of electrical installations and how to achieve approvals for them. Understanding and accurately applying the National Electrical Code is key to successful prefab initiatives. 

Section 110.2 addresses approvals generally and applies to equipment and systems covered by the Code. From a practical perspective, one could surmise that on-site and remote prefabrication is already covered in the approval requirements. This is a valid assumption. However, challenges and inconsistencies do exist, as the term “prefabrication” is not yet mentioned in the NEC.

Complicating matters even more, jurisdictions at the state and local level may have additional unique regulations or amendments that handle this issue, and many do not address it all. The saying, “When in Rome, do as the Romans do,” has value when it comes to prefabrication processes. The processes can differ widely between jurisdictions, which can lead to inconsistency.

What’s in the Code?

In the NEC, approved is defined as “acceptable to the authority having jurisdiction.” The authority having jurisdiction (AHJ) is typically the jurisdiction’s building official who deputizes field inspectors to issue approvals during inspections. Note that other codes and standards may define and use “approved” differently.

The NEC clearly outlines the responsibilities of the AHJ in Section 90.4. This section simply indicates that the AHJ has the responsibility for interpreting the Code rules and issuing approvals. Another element of the approval process is granting special permission, which is also the AHJ’s responsibility. Special permission is typically handled by jurisdictions through a variance or modification process, usually formally and in writing. Special permission is defined by the NEC in Article 100 as the written consent of the AHJ.

Section 110.2 outlines the foundation of the approval process by indicating that conductors and equipment required or permitted by the NEC are acceptable only if approved. This requirement places the responsibility of the approving process squarely on the shoulders of the AHJ. Inspectors have the authority to approve any installation and use any criteria as the basis for such approvals. Product certification or listing often serves as a basis for inspector approvals.

The NEC does not globally require that all equipment be certified (listed). There are some specific NEC rules that do require certain wiring methods and materials to be certified (listed), but such a requirement will usually be contained within the specific rule applicable to the equipment and installation, including prefabricated electrical installations assembled either on-site or remotely. This involves communication and coordination processes important to reduce costly delays in job-site production.

Achieving approvals

The objectives are to achieve approval of the prefabricated installation or equipment (constructed either on-site or remotely) and providing evidence of such inspection and approval for the inspecting authority responsible for approval. There are a few methods for demonstrating that prefabricated installation has been inspected for Code compliance. These include equipment listing or labeling, evidence of equipment evaluation from a qualified testing laboratory or inspection agency concerned with product evaluation, evidence acceptable to the AHJ such as a manufacturer’s self-­evaluation or an owner’s engineering judgment or engineering report, or evidence of compliance or approval by the applicable AHJ or other inspection documentation.

 Keep in mind that the approval processes related to electrical prefabrication can vary. The AHJ can approve any installation, and they often must use much more criteria to determine compliance and ultimately issue approvals. The NEC compliance and the suitability of prefabbed electrical installations should be verified and carefully considered by the (AHJ) inspector when fulfilling their approving duties.

Whether the prefabrication happens remotely or on-site, the inspection and approval processes apply. Communication and coordination between responsible parties and the AHJ are essential in construction processes, including prefabrication. 

The additional efforts on the front end of this process will undoubtedly result in efficiency in the completion of electrical installations that are Code compliant and have received the required approval from the AHJ.

Header image: Rosendin Electric