During a teacher strike last year, my 7-year-old had the impromptu opportunity to join me on the field evaluation of an industrial machine. Having familiarity with the end user, they were kind enough to permit her on site and even gave her a tour of their metal casting plant. In professional jest, they told her how important my inspection was to their operation and that my job entailed “playing with stickers all day”. No doubt they had heard my frequent rant about how field labels are not just fancy little stickers and knew full well that that comment would get a long run, as my daughter still repeats it to this day with a smirk.

To understand the significance of field evaluating unlabeled electrical equipment, it is helpful to appreciate the effort that goes into the process of listing an electrical equipment. The listing or labeling of any product should really begin with the inception of a product lifecycle, meaning the manufacturer must have the foresight to incorporate compliance with the product safety standard at the earliest stages of development. During business conception, the impending cost and compromise to final design is a significant commitment to achieving a certificate of compliance as part of the product launch.

The third-party responsible for validating the final design is called the Nationally Recognized Testing Laboratory (NRTL), which are OSHA recognized Testing and Certification Bodies that hold accreditation for performing conformity assessment, inspections and testing services These services are not free, but necessary by US law, so costs are amortized and shared amongst the manufacturers in the form of application and administration fees, labor for evaluation and testing and documentation, maintenance of the license to bear the NRTL mark, and publication of the certificate.

Technical documents are prescribed by each consensus safety standard, and generally include details of the construction and instructions for safe operation and maintenance. To underwrite a product design, the NRTL will at a minimum require electrical schematics, layout drawings, and bill of materials – the latter of which should include make, model, critical specification, and approval for each component of the product. A portfolio of each component certification may also be necessary and sometimes additional testing of sub-components to their respective safety standards is required. Based on the technical documentation, the NRTL staff will compare the unique product design with the criteria to confirm compliance, identify non-compliances, and develop a test plan.

Test performance is also prescribed by each standard and will include single-fault conditions generic to all electrical equipment (i.e. short-circuit, ground-faults, etc.) and fault conditions specific to the application (i.e. operator error, loss of coolant, etc.). Samples that are representative of the final production must be provided by the manufacture per the developed test plan, and since testing may be destructive, several samples could be necessary. Duration of the test application and thoroughness of data collection, as mandated by the laboratory accreditation, can take weeks to months to complete – that is if design is compliant, and even longer if the initial results do not pass. At the end of an investigation, the NRTL staff will provide the official test report to documents compliance and results of testing, all justification and consideration for passing judgment, and the test methods, test conditions, and test equipment used for validation.

The last step is to conduct a factory inspection that verifies the sample evaluated and tested is representative of the final production. The NRTL staff will visit the factory and perform an equally thorough evaluation of the manufacturing facility and its processes. This includes an audit of the quality manual pertaining to all personnel involved in the production, and all materials and assemblies used in construction of the product. Procedures are reviewed at each stage of receiving, storage, assembly, production testing and shipping for the components and products. All purchase orders, records of production line testing, and equipment calibration must be retained for the following periodic inspections. Even product improvement, returns or service records, and customer complaints must be retained for future reference. If an issue is discovered after a product reaches the market, then the manufacturer must have traceability to the production records.

All this effort is done to satisfy the very definition of “Listed” found in Article 100 of the National Electrical Code:

Equipment, materials, or services included in a list published by an organization that is acceptable to the authority having jurisdiction and concerned with evaluation of products or services, that maintains periodic inspection of production of listed equipment or materials or periodic evaluation of services, and whose listing states that either the equipment, material, or service meets appropriate designated standards or has been tested and found suitable for a specified purpose.

While little of this background may seem relevant to the installer of an unlabeled electrical equipment that was flagged by the Authority Having Jurisdiction (AHJ), every aspect of that Listing process is addressed within the Recommended Practice and Procedure for Unlabeled Electrical Equipment Evaluations (NFPA 791). The difference is that now the evaluation must be performed in the field, in front of spectators, with limited construction data and test information, to collect empirical evidence without causing damage, and often while avoiding job hazards that are driving their forklifts through your working space.

“The AHJ just wants to see a sticker on the equipment” declares the installer. My response is emphatic: It is not a fancy little sticker; my daughter plays with those at home … this here is a field label, it has a serial number!



David Falk is a Compliance Engineer at Southwest Energy Systems. He is responsible for field evaluations of unlabeled and modified electrical equipment. He has 13 years as field engineer in Electrical Industry including product development, systems integration, and regulatory compliance of alternative/renewable energies and industrial machinery.In addition, David is the second vice president for the Central Arizona Chapter of the International Association of Electrical Inspectors (IAEI). He was a Program Manager of Field Services and Senior Test Engineer at TUV Rheinland from 2011-2018 before joining the SES team.